Paul Wender
Francis W. Bergstrom Professor and Professor, by courtesy, of Chemical and Systems Biology
Chemistry
Bio
The Wender Group addresses unsolved problems in chemistry, synthesis, biology, medicine, and materials science using new computational tools, new reactions, reagents, strategies and design. Leveraging affiliations with the Medical School, Imaging Center, Chemical Biology Program and Molecular Therapeutics Program as well as numerous internal and external collaborations, the lab emphasizes the use of chemistry, design and synthesis to address problems of significance in biology and medicine, including eradication of HIV/AIDS, overcoming resistant cancer, cancer immunotherapy and treating cognitive disorders such as Alzheimer's disease.
Paul Wender received his B.S. degree from Wilkes University and his Ph.D. in chemistry from Yale University. He was an NIH Postdoctoral Fellow at Columbia University. He served on the faculty at Harvard University and joined the faculty at Stanford University where he is the Francis W. Bergstrom Professor of Chemistry and holds a courtesy appointment in the Department of Chemical and Systems Biology. Professor Wender’s research has been recognized with numerous awards including recently the Tetrahedron Prize, Prelog Medal (Swiss Federal Institute of Technology), Arthur Cope Award (American Chemical Society), Cohen Award for Excellence in Medicinal Chemistry (Israel Chemical Society), and Research Award of the German Bioactives and Biotechnology Leibniz Allaince. He has also been recognized with several teaching awards including the Hoagland Prize, Bing Teaching Award, and the Dean's Teaching Award. He is an elected member of the US National Academy of Sciences, a foreign member of the Royal Spanish Academy of Sciences, and a fellow of the American Association for the Advancement of Science and the American Academy of Arts and Sciences.
Academic Appointments
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Professor, Chemistry
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Professor (By courtesy), Chemical and Systems Biology
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Member, Bio-X
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Faculty Fellow, Sarafan ChEM-H
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Member, Stanford Cancer Institute
Honors & Awards
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Research Award of the German Bioactives and Biotechnology, Leibniz Alliance (2016)
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Arthur C. Cope Award, American Chemical Society (2015)
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Cohen Award for Excellence in Medicinal Chemistry, Israel Chemical Society (2015)
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Office of Technology Licensing Innovator Award, Stanford University (2015)
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Prelog Medal, ETH, Switzerland (2013)
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Tetrahedron Prize for Creativity in Organic Chemistry, Tetrahedron Publications (2012)
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Wilbur Lucius Cross Medal (Yale Graduate Alumni), Yale University (2010)
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The Hamilton Award, University of Nebraska (2008)
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MERIT Award, National Institutes of Health (2006)
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H.C. Brown Award for Creative Research in Synthetic Methods, American Chemical Society (2003)
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MERIT Award, National Institutes of Health (2003)
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Member, National Academy of Science (2003)
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Fellow, American Association for the Advancement of Science (2001)
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Dean's Award for Distinguished Teaching, Stanford University (2000)
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Award for Creative work in Synthetic Organic Chemistry, American Chemical Society (1998)
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Pfizer Research Award for Synthetic Organic Chemistry, American Chemical Society (1995)
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Bing Teaching Award, Stanford University (1992)
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Fellow, American Academy of Arts and Sciences (1992)
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ASSU Teaching Award, Stanford University ASSU (1991)
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Alexander von Humboldt Stiftung Award, Alexander von Humboldt Foundation (1991)
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Hoagland Prize for Undergraduate Teaching, Stanford University (1991)
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Arthur C. Cope Scholar Award, American Chemical Society (1990)
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Ernest Guenther Award, American Chemical Society (1988)
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Stuart Award for Excellence in Chemistry, ICI Pharmaceutical Group (1988)
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Dreyfus Teacher Scholar Award, Camille and Henry Dreyfus Foundation (1980)
Professional Education
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Ph.D., Yale University, Chemistry (1973)
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B.S., Wilkes College, Chemistry (1969)
Patents
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Paul Wender, Jung-Min Kee, Jeffrey Warrington. "United States Patent 8,067,632 A Process to Produce Prostratin and Structural or Functional Analogs Thereof", Leland Stanford Junior University, Nov 29, 2011
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Christina Cooley, Erika Geihe Stanzl, Robert Waymouth, Paul Wender. "United States Patent 61,531,495 Amphipathic Co-Oligomers for the Delivery of SIRNA", Leland Stanford Junior University, Sep 11, 2011
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Paul Wender, Lars Heumann, Rainer Kramer, Carolyn Gauntlett, Elizabeth Beans. "United States Patent 12/839,808 Prostratin Analogs, Bryostatin Analogs, Prodrugs, Synthetic Methods, and Methods of Use", Leland Stanford Junior University, Jul 20, 2010
Current Research and Scholarly Interests
Molecular imaging, therapeutics, drug delivery, drug mode of action, synthesis
2024-25 Courses
- Organic Polyfunctional Compounds
CHEM 123 (Aut) -
Independent Studies (6)
- Advanced Undergraduate Research
CHEM 190 (Aut, Win, Spr, Sum) - Directed Instruction/Reading
CHEM 90 (Aut, Win, Spr, Sum) - Master's Research
MATSCI 200 (Aut, Win, Spr, Sum) - Out-of-Department Undergraduate Research
BIO 199X (Aut, Win, Spr, Sum) - Research and Special Advanced Work
CHEM 200 (Aut, Win, Spr, Sum) - Research in Chemistry
CHEM 301 (Aut, Win, Spr, Sum)
- Advanced Undergraduate Research
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Prior Year Courses
2023-24 Courses
- Advanced Organic Chemistry I
CHEM 221 (Aut)
2022-23 Courses
- Advanced Organic Chemistry I
CHEM 221 (Aut) - Structure and Reactivity of Organic Molecules
CHEM 33 (Win)
2021-22 Courses
- Advanced Organic Chemistry I
CHEM 221 (Aut) - Structure and Reactivity of Organic Molecules
CHEM 33 (Win)
- Advanced Organic Chemistry I
Stanford Advisees
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Doctoral Dissertation Reader (AC)
Hayden Anderson, Lawrence Berg, Amy Laturski, KE ZHENG -
Postdoctoral Faculty Sponsor
Adam Cook, You Jin Jung, Sukhun Lee, Pavan Yadav -
Doctoral Dissertation Advisor (AC)
Rami Hourani, Zhijian Li, Owen McAteer
All Publications
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Topological Heterogeneity of Protein Kinase C Modulators in Human T-Cells Resolved with In-Cell Dynamic Nuclear Polarization NMR Spectroscopy.
Journal of the American Chemical Society
2024
Abstract
Phorbol ester analogs are a promising class of anticancer therapeutics and HIV latency reversing agents that interact with cellular membranes to recruit and activate protein kinase C (PKC) isoforms. However, it is unclear how these esters interact with membranes and how this might correlate with the biological activity of different phorbol ester analogs. Here, we have employed dynamic nuclear polarization (DNP) NMR to characterize phorbol esters in a native cellular context. The enhanced NMR sensitivity afforded by DNP and cryogenic operation reveals topological heterogeneity of 13C-21,22-phorbol-myristate-acetate (PMA) within T cells utilizing 13C-13C correlation and double quantum filtered NMR spectroscopy. We demonstrate the detection of therapeutically relevant amounts of PMA in T cells down to an upper limit of 60.0 pmol per million cells and identify PMA to be primarily localized in cellular membranes. Furthermore, we observe distinct 13C-21,22-PMA chemical shifts under DNP conditions in cells compared to model membrane samples and homogenized cell membranes, that cannot be accounted for by differences in conformation. We provide evidence for distinct membrane topologies of 13C-21,22-PMA in cell membranes that are consistent with shallow binding modes. This is the first of its kind in-cell DNP characterization of small molecules dissolved in the membranes of living cells, establishing in-cell DNP-NMR as an important method for the characterization of drug-membrane interactions within the context of the complex heterogeneous environment of intact cellular membranes. This work sets the stage for the identification of the in-cell structural interactions that govern the biological activity of phorbol esters.
View details for DOI 10.1021/jacs.4c05704
View details for PubMedID 39322225
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Biguanide-Vancomycin Conjugates are Effective Broad-Spectrum Antibiotics against Actively Growing and Biofilm-Associated Gram-Positive and Gram-Negative ESKAPE Pathogens and Mycobacteria.
Journal of the American Chemical Society
2024
Abstract
Strategies to increase the efficacy and/or expand the spectrum of activity of existing antibiotics provide a potentially fast path to clinically address the growing crisis of antibiotic-resistant infections. Here, we report the synthesis, antibacterial efficacy, and mechanistic activity of an unprecedented class of biguanide-antibiotic conjugates. Our lead biguanide-vancomycin conjugate, V-C6-Bg-PhCl (5e), induces highly effective cell killing with up to a 2 orders-of-magnitude improvement over its parent compound, vancomycin (V), against vancomycin-resistant enterococcus. V-C6-Bg-PhCl (5e) also exhibits improved activity against mycobacteria and each of the ESKAPE pathogens, including the Gram-negative organisms. Furthermore, we uncover broad-spectrum killing activity against biofilm-associated Gram-positive and Gram-negative bacteria as well as mycobacteria not observed for clinically used antibiotics such as oritavancin. Mode-of-action studies reveal that vancomycin-like cell wall synthesis inhibition with improved efficacy attributed to enhanced engagement at vancomycin binding sites through biguanide association with relevant cell-surface anions for Gram-positive and Gram-negative bacteria. Due to its potency, remarkably broad activity, and lack of acute mammalian cell toxicity, V-C6-Bg-PhCl (5e) is a promising candidate for treating antibiotic-resistant infections and notoriously difficult-to-treat slowly growing and antibiotic-tolerant bacteria associated with chronic and often incurable infections. More generally, this study offers a new strategy (biguanidinylation) to enhance antibiotic activity and facilitate clinical entry.
View details for DOI 10.1021/jacs.4c06520
View details for PubMedID 39088791
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Isoprenoid CARTs: In Vitro and In Vivo mRNA Delivery by Charge-Altering Releasable Transporters Functionalized with Archaea-inspired Branched Lipids.
Biomacromolecules
2024
Abstract
The delivery of oligonucleotides across biological barriers is a challenge of unsurpassed significance at the interface of materials science and medicine, with emerging clinical utility in prophylactic and therapeutic vaccinations, immunotherapies, genome editing, and cell rejuvenation. Here, we address the role of readily available branched lipids in the design, synthesis, and evaluation of isoprenoid charge-altering releasable transporters (CARTs), a pH-responsive oligomeric nanoparticle delivery system for RNA. Systematic variation of the lipid block reveals an emergent relationship between the lipid block and the neutralization kinetics of the polycationic block. Unexpectedly, iA21A11, a CART with the smallest lipid side chain, isoamyl-, was identified as the lead isoprenoid CART for the in vitro transfection of immortalized lymphoblastic cell lines. When administered intramuscularly in a murine model, iA21A11-mRNA complexes induce higher protein expression levels than our previous lead CART, ONA. Isoprenoid CARTs represent a new delivery platform for RNA vaccines and other polyanion-based therapeutics.
View details for DOI 10.1021/acs.biomac.4c00373
View details for PubMedID 38814265
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Organ- and Cell-Selective Delivery of mRNA In Vivo Using Guanidinylated Serinol Charge-Altering Releasable Transporters.
Journal of the American Chemical Society
2024
Abstract
Selective RNA delivery is required for the broad implementation of RNA clinical applications, including prophylactic and therapeutic vaccinations, immunotherapies for cancer, and genome editing. Current polyanion delivery relies heavily on cationic amines, while cationic guanidinium systems have received limited attention due in part to their strong polyanion association, which impedes intracellular polyanion release. Here, we disclose a general solution to this problem in which cationic guanidinium groups are used to form stable RNA complexes upon formulation but at physiological pH undergo a novel charge-neutralization process, resulting in RNA release. This new delivery system consists of guanidinylated serinol moieties incorporated into a charge-altering releasable transporter (GSer-CARTs). Significantly, systematic variations in structure and formulation resulted in GSer-CARTs that exhibit highly selective mRNA delivery to the lung (97%) and spleen (98%) without targeting ligands. Illustrative of their breadth and translational potential, GSer-CARTs deliver circRNA, providing the basis for a cancer vaccination strategy, which in a murine model resulted in antigen-specific immune responses and effective suppression of established tumors.
View details for DOI 10.1021/jacs.4c02704
View details for PubMedID 38743019
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Defining the Effects of PKC Modulator HIV Latency-Reversing Agents on Natural Killer Cells.
Pathogens & immunity
2024; 9 (1): 108-137
Abstract
Latency reversing agents (LRAs) such as protein kinase C (PKC) modulators can reduce rebound-competent HIV reservoirs in small animal models. Furthermore, administration of natural killer (NK) cells following LRA treatment improves this reservoir reduction. It is currently unknown why the combination of a PKC modulator and NK cells is so potent and whether exposure to PKC modulators may augment NK cell function in some way.Primary human NK cells were treated with PKC modulators (bryostatin-1, prostratin, or the designed, synthetic bryostatin-1 analog SUW133), and evaluated by examining expression of activation markers by flow cytometry, analyzing transcriptomic profiles by RNA sequencing, measuring cytotoxicity by co-culturing with K562 cells, assessing cytokine production by Luminex assay, and examining the ability of cytokines and secreted factors to independently reverse HIV latency by co-culturing with Jurkat-Latency (J-Lat) cells.PKC modulators increased expression of proteins involved in NK cell activation. Transcriptomic profiles from PKC-treated NK cells displayed signatures of cellular activation and enrichment of genes associated with the NFκB pathway. NK cell cytotoxicity was unaffected by prostratin but significantly decreased by bryostatin-1 and SUW133. Cytokines from PKC-stimulated NK cells did not induce latency reversal in J-Lat cell lines.Although PKC modulators have some significant effects on NK cells, their contribution in "kick and kill" strategies is likely due to upregulating HIV expression in CD4+ T cells, not directly enhancing the effector functions of NK cells. This suggests that PKC modulators are primarily augmenting the "kick" rather than the "kill" arm of this HIV cure approach.
View details for DOI 10.20411/pai.v9i1.673
View details for PubMedID 38765786
View details for PubMedCentralID PMC11101012
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TPPB modulates PKC activity to attenuate neuroinflammation and ameliorate experimental multiple sclerosis.
bioRxiv : the preprint server for biology
2024
Abstract
Protein kinase C (PKC) plays a key role in modulating the activities of the innate immune cells of the central nervous system (CNS). A delicate balance between pro-inflammatory and regenerative activities by microglia and CNS-associated macrophages is necessary for the proper functioning of the CNS. Thus, a maladaptive activation of these CNS innate immune cells results in neurodegeneration and demyelination associated with various neurologic disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Prior studies have demonstrated that modulation of PKC activity by bryostatin-1 (bryo-1) and its analogs (bryologs) attenuates the pro-inflammatory processes by microglia/CNS macrophages and alleviates the neurologic symptoms in experimental autoimmune encephalomyelitis (EAE), an MS animal model. Here, we demonstrate that (2S,5S)-(E,E)-8-(5-(4(trifluoromethyl)phenyl)-2,4-pentadienoylamino)benzolactam (TPPB), a structurally distinct PKC modulator, has a similar effect to bryo-1 on CNS innate immune cells both in vitro and in vivo, attenuating neuroinflammation and resulting in CNS regeneration and repair. This study identifies a new structural class of PKC modulators, which can therapeutically target CNS innate immunity as a strategy to treat neuroinflammatory and neurodegenerative disorders.
View details for DOI 10.1101/2024.02.02.578637
View details for PubMedID 38370818
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Vancomycin-Polyguanidino Dendrimer Conjugates Inhibit Growth of Antibiotic-Resistant Gram-Positive and Gram-Negative Bacteria and Eradicate Biofilm-AssociatedS.aureus.
ACS infectious diseases
2024
Abstract
The global challenge of antibiotic resistance necessitates the introduction of more effective antibiotics. Here we report a potentially general design strategy, exemplified with vancomycin, that improves and expands antibiotic performance. Vancomycin is one of the most important antibiotics in use today for the treatment of Gram-positive infections. However, it fails to eradicate difficult-to-treat biofilm populations. Vancomycin is also ineffective in killing Gram-negative bacteria due to its inability to breach the outer membrane. Inspired by our seminal studies on cell penetrating guanidinium-rich transporters (e.g., octaarginine), we recently introduced vancomycin conjugates that effectively eradicate Gram-positive biofilm bacteria, persister cells and vancomycin-resistant enterococci (with V-r8, vancomycin-octaarginine), and Gram-negative pathogens (with V-R, vancomycin-arginine). Having shown previously that the spatial array (linear versus dendrimeric) of multiple guanidinium groups affects cell permeation, we report here for the first time vancomycin conjugates with dendrimerically displayed guanidinium groups that exhibit superior efficacy and breadth, presenting the best activity of V-r8 and V-R in single broad-spectrum compounds active against ESKAPE pathogens. Mode-of-action studies reveal cell-surface activity and enhanced vancomycin-like killing. The vancomycin-polyguanidino dendrimer conjugates exhibit no acute mammalian cell toxicity or hemolytic activity. Our study introduces a new class of broad-spectrum vancomycin derivatives and a general strategy to improve or expand antibiotic performance through combined mode-of-action and function-oriented design studies.
View details for DOI 10.1021/acsinfecdis.3c00168
View details for PubMedID 38252999
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TPPB modulates PKC activity to attenuate neuroinflammation and ameliorate experimental multiple sclerosis.
Frontiers in cellular neuroscience
2024; 18: 1373557
Abstract
Protein kinase C (PKC) plays a key role in modulating the activities of the innate immune cells of the central nervous system (CNS). A delicate balance between pro-inflammatory and regenerative activities by microglia and CNS-associated macrophages is necessary for the proper functioning of the CNS. Thus, a maladaptive activation of these CNS innate immune cells results in neurodegeneration and demyelination associated with various neurologic disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Prior studies have demonstrated that modulation of PKC activity by bryostatin-1 (bryo-1) and its analogs (bryologs) attenuates the pro-inflammatory processes by microglia/CNS macrophages and alleviates the neurologic symptoms in experimental autoimmune encephalomyelitis (EAE), an MS animal model. Here, we demonstrate that (2S,5S)-(E,E)-8-(5-(4-(trifluoromethyl)phenyl)-2,4-pentadienoylamino)benzolactam (TPPB), a structurally distinct PKC modulator, has a similar effect to bryo-1 on CNS innate immune cells both in vitro and in vivo, attenuating neuroinflammation and resulting in CNS regeneration and repair. This study identifies a new structural class of PKC modulators, which can therapeutically target CNS innate immunity as a strategy to treat neuroinflammatory and neurodegenerative disorders.
View details for DOI 10.3389/fncel.2024.1373557
View details for PubMedID 38841204
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Defining the Effects of PKC Modulator HIV Latency-Reversing Agents on Natural Killer Cells
Pathogens and Immunity
2024; 9 (1): 108 - 137
View details for DOI 10.20411/pai.v9i1.673
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Immunologic and virologic parameters associated with HIV DNA reservoir size in people living with HIV receiving antiretroviral therapy.
The Journal of infectious diseases
2023
Abstract
A better understanding of the dynamics of HIV reservoirs in CD4+ T cells of people with HIV (PWH) receiving antiretroviral therapy (ART) is crucial for developing therapies to eradicate the virus.We conducted a study involving 28 aviremic PWH receiving ART with high and low levels of HIV DNA. We analyzed immunologic and virologic parameters and their association with the HIV reservoir size.The frequency of CD4+ T cells carrying HIV DNA was associated with higher pre-ART plasma viremia, lower pre-ART CD4+ T cell counts, and lower pre-ART CD4/CD8 ratios. During ART, the High group maintained elevated levels of intact HIV proviral DNA, cell-associated HIV RNA, and inducible virion-associated HIV RNA. HIV sequence analysis showed no evidence for preferential accumulation of defective proviruses nor higher frequencies of clonal expansion in the High versus Low group. Phenotypic and functional T-cell analyses did not show enhanced immune-mediated virologic control in the Low versus High group. Of considerable interest, pre-ART innate immunity was significantly higher in the Low versus High group.Our data suggest that innate immunity at the time of ART initiation may play an important role in modulating the dynamics and persistence of viral reservoirs in PWH.
View details for DOI 10.1093/infdis/jiad595
View details for PubMedID 38128541
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Charge-altering releasable transporters enhance mRNA delivery in vitro and exhibit in vivo tropism.
Nature communications
2023; 14 (1): 6983
Abstract
The introduction of more effective and selective mRNA delivery systems is required for the advancement of many emerging biomedical technologies including the development of prophylactic and therapeutic vaccines, immunotherapies for cancer and strategies for genome editing. While polymers and oligomers have served as promising mRNA delivery systems, their efficacy in hard-to-transfect cells such as primary T lymphocytes is often limited as is their cell and organ tropism. To address these problems, considerable attention has been placed on structural screening of various lipid and cation components of mRNA delivery systems. Here, we disclose a class of charge-altering releasable transporters (CARTs) that differ from previous CARTs based on their beta-amido carbonate backbone (bAC) and side chain spacing. These bAC-CARTs exhibit enhanced mRNA transfection in primary T lymphocytes in vitro and enhanced protein expression in vivo with highly selective spleen tropism, supporting their broader therapeutic use as effective polyanionic delivery systems.
View details for DOI 10.1038/s41467-023-42672-x
View details for PubMedID 37914693
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Conjugation of Vancomycin with a Single Arginine Improves Efficacy against Mycobacteria by More Effective Peptidoglycan Targeting.
Journal of medicinal chemistry
2023
Abstract
Drug resistant bacterial infections have emerged as one of the greatest threats to public health. The discovery and development of new antimicrobials and anti-infective strategies are urgently needed to address this challenge. Vancomycin is one of the most important antibiotics for the treatment of Gram-positive infections. Here, we introduce the vancomycin-arginine conjugate (V-R) as a highly effective antimicrobial against actively growing mycobacteria and difficult-to-treat mycobacterial biofilm populations. Further improvement in efficacy through combination treatment of V-R to inhibit peptidoglycan synthesis and ethambutol to inhibit arabinogalactan synthesis underscores the ability to identify compound synergies to more effectively target the Achilles heel of the cell-wall assembly. Moreover, we introduce mechanistic activity data and a molecular model derived from a d-Ala-d-Ala-bound vancomycin structure that we hypothesize underlies the molecular basis for the antibacterial improvement attributed to the arginine modification that is specific to peptidoglycan chemistry employed by mycobacteria and distinct from Gram-positive pathogens.
View details for DOI 10.1021/acs.jmedchem.3c00565
View details for PubMedID 37477249
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Detection of intact vancomycin-arginine as the active antibacterial conjugate in E. coli by whole-cell solid-state NMR.
RSC medicinal chemistry
2023; 14 (6): 1192-1198
Abstract
The introduction of new and improved antibacterial agents based on facile synthetic modifications of existing antibiotics represents a promising strategy to deliver urgently needed antibacterial candidates to treat multi-drug resistant bacterial infections. Using this strategy, vancomycin was transformed into a highly active agent against antibiotic-resistant Gram-negative organisms in vitro and in vivo through the addition of a single arginine to yield vancomycin-arginine (V-R). Here, we report detection of the accumulation of V-R in E. coli by whole-cell solid-state NMR using 15N-labeled V-R. 15N CPMAS NMR revealed that the conjugate remained fully amidated without loss of arginine, demonstrating that intact V-R represents the active antibacterial agent. Furthermore, C{N}REDOR NMR in whole cells with all carbons at natural abundance 13C levels exhibited the sensitivity and selectivity to detect the directly bonded 13C-15N pairs of V-R within E. coli cells. Thus, we also present an effective methodology to directly detect and evaluate active drug agents and their accumulation within bacteria without the need for potentially perturbative cell lysis and analysis protocols.
View details for DOI 10.1039/d3md00173c
View details for PubMedID 37360389
View details for PubMedCentralID PMC10285746
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Detection of intact vancomycin-arginine as the active antibacterial conjugate in E. coli by whole-cell solid-state NMR
RSC MEDICINAL CHEMISTRY
2023
View details for DOI 10.1039/d3md00173c
View details for Web of Science ID 000997162500001
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Circular RNA vaccine induces potent T cell responses.
Proceedings of the National Academy of Sciences of the United States of America
2023; 120 (20): e2302191120
Abstract
Circular RNAs (circRNAs) are a class of RNAs commonly found across eukaryotes and viruses, characterized by their resistance to exonuclease-mediated degradation. Their superior stability compared to linear RNAs, combined with previous work showing that engineered circRNAs serve as efficient protein translation templates, make circRNA a promising candidate for RNA medicine. Here, we systematically examine the adjuvant activity, route of administration, and antigen-specific immunity of circRNA vaccination in mice. Potent circRNA adjuvant activity is associated with RNA uptake and activation of myeloid cells in the draining lymph nodes and transient cytokine release. Immunization of mice with engineered circRNA encoding a protein antigen delivered by a charge-altering releasable transporter induced innate activation of dendritic cells, robust antigen-specific CD8 T cell responses in lymph nodes and tissues, and strong antitumor efficacy as a therapeutic cancer vaccine. These results highlight the potential utility of circRNA vaccines for stimulating potent innate and T cell responses in tissues.
View details for DOI 10.1073/pnas.2302191120
View details for PubMedID 37155869
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Lysine-Derived Charge-Altering Releasable Transporters: Targeted Delivery of mRNA and siRNA to the Lungs.
Bioconjugate chemistry
2023
Abstract
Targeted delivery of nucleic acid therapeutics to the lungs could transform treatment options for pulmonary disease. We have previously developed oligomeric charge-altering releasable transporters (CARTs) for in vivo mRNA transfection and demonstrated their efficacy for use in mRNA-based cancer vaccination and local immunomodulatory therapies against murine tumors. While our previously reported glycine-based CART-mRNA complexes (G-CARTs/mRNA) show selective protein expression in the spleen (mouse, >99%), here, we report a new lysine-derived CART-mRNA complex (K-CART/mRNA) that, without additives or targeting ligands, shows selective protein expression in the lungs (mouse, >90%) following systemic IV administration. We further show that by delivering siRNA using the K-CART, we can significantly decrease expression of a lung-localized reporter protein. Blood chemistry and organ pathology studies demonstrate that K-CARTs are safe and well-tolerated. We report on the new step economical, organocatalytic synthesis (two steps) of functionalized polyesters and oligo-carbonate-co-α-aminoester K-CARTs from simple amino acid and lipid-based monomers. The ability to direct protein expression selectively in the spleen or lungs by simple, modular changes to the CART structure opens fundamentally new opportunities in research and gene therapy.
View details for DOI 10.1021/acs.bioconjchem.3c00019
View details for PubMedID 36996808
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Secreted factors induced by PKC modulators do not indirectly cause HIV latency reversal.
Virology
2023; 581: 8-14
Abstract
HIV can establish a long-lived latent infection in cells harboring integrated non-expressing proviruses. Latency reversing agents (LRAs), including protein kinase C (PKC) modulators, can induce expression of latent HIV, thereby reducing the latent reservoir in animal models. However, PKC modulators such as bryostatin-1 also cause cytokine upregulation in peripheral blood mononuclear cells (PBMCs), including cytokines that might independently reverse HIV latency. To determine whether cytokines induced by PKC modulators contribute to latency reversal, primary human PBMCs were treated with bryostatin-1 or the bryostatin analog SUW133, a superior LRA, and supernatant was collected. As anticipated, LRA-treated cell supernatant contained increased levels of cytokines compared to untreated cell supernatant. However, exposure of latently-infected cells with this supernatant did not result in latency reactivation. These results indicate that PKC modulators do not have significant indirect effects on HIV latency reversal in vitro and thus are targeted in their latency reversing ability.
View details for DOI 10.1016/j.virol.2023.02.009
View details for PubMedID 36842270
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Comprehensive analysis of HIV reservoirs in elite controllers.
The Journal of clinical investigation
2023; 133 (3)
View details for DOI 10.1172/JCI165446
View details for PubMedID 36719383
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Trimethylene Methane Dianion Equivalent for the Asymmetric Consecutive Allylation of Aldehydes: Applications to Prins-Driven Macrocyclizations for the Synthesis of Bryostatin 1 and Analogues.
The Journal of organic chemistry
2022
Abstract
We report a one-step (one-flask) generation and reaction of a bifunctional allylating reagent, a trimethylene methane dianion equivalent, that provides a route for the asymmetric 2-(trimethylsilylmethyl) allylation of aldehydes. The product of the first aldehyde allylation process is then set to engage in a second separate aldehyde allylation, providing an improved Prins macrocyclization strategy both for the scalable synthesis of bryostatin 1 and for the total synthesis of a new potent bryostatin analogue.
View details for DOI 10.1021/acs.joc.2c02047
View details for PubMedID 36378802
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Practical synthesis of the therapeutic leads tigilanol tiglate and its analogues.
Nature chemistry
2022
Abstract
Tigilanol tiglate is a natural product diterpenoid in clinical trials for the treatment of a broad range of cancers. Its unprecedented protein kinase C isoform selectivity make it and its analogues exceptional leads for PKC-related clinical indications, which include human immunodeficiency virus and AIDS eradication, antigen-enhanced cancer immunotherapy, Alzheimer's disease and multiple sclerosis. Currently, the only source of tigilanol tiglate is a rain forest tree, Fontainea picrosperma, whose limited number and restricted distribution (northeastern Australia) has prompted consideration of designed tree plantations to address supply needs. Here we report a practical laboratory synthesis of tigilanol tiglate that proceeds in 12 steps (12% overall yield, >80% average yield per step) and can be used to sustainably supply tigilanol tiglate and its analogues, the latter otherwise inaccessible from the natural source. The success of this synthesis is based on a unique strategy for the installation of an oxidation pattern common to many biologically active tiglianes, daphnanes and their analogues.
View details for DOI 10.1038/s41557-022-01048-2
View details for PubMedID 36192432
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Author Correction: Engineering circular RNA for enhanced protein production.
Nature biotechnology
2022
View details for DOI 10.1038/s41587-022-01472-2
View details for PubMedID 35978134
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Engineering circular RNA for enhanced protein production.
Nature biotechnology
2022
Abstract
Circular RNAs (circRNAs) are stable and prevalent RNAs in eukaryotic cells that arise from back-splicing. Synthetic circRNAs and some endogenous circRNAs can encode proteins, raising the promise of circRNA as a platform for gene expression. In this study, we developed a systematic approach for rapid assembly and testing of features that affect protein production from synthetic circRNAs. To maximize circRNA translation, we optimized five elements: vector topology, 5' and 3' untranslated regions, internal ribosome entry sites and synthetic aptamers recruiting translation initiation machinery. Together, these design principles improve circRNA protein yields by several hundred-fold, provide increased translation over messenger RNA in vitro, provide more durable translation in vivo and are generalizable across multiple transgenes.
View details for DOI 10.1038/s41587-022-01393-0
View details for PubMedID 35851375
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Fingolimod-Conjugated Charge-Altering Releasable Transporters Efficiently and Specifically Deliver mRNA to Lymphocytes In Vivo and In Vitro.
Biomacromolecules
2022
Abstract
Charge-altering releasable transporters (CARTs) are a class of oligonucleotide delivery vehicles shown to be effective for delivery of messenger RNA (mRNA) both in vitro and in vivo. Here, we exploited the chemical versatility of the CART synthesis to generate CARTs containing the small-molecule drug fingolimod (FTY720) as a strategy to increase mRNA delivery and expression in lymphocytes through a specific ligand-receptor interaction. Fingolimod is an FDA-approved small-molecule drug that, upon in vivo phosphorylation, binds to the sphingosine-1-phosphate receptor 1 (S1P1), which is highly expressed on lymphocytes. Compared to its non-fingolimod-conjugated analogue, the fingolimod-conjugated CART achieved superior transfection of activated human and murine T and B lymphocytes in vitro. The higher transfection of the fingolimod-conjugated CARTs was lost when cells were exposed to a free fingolimod before transfection. In vivo, the fingolimod-conjugated CART showed increased mRNA delivery to marginal zone B cells and NK cells in the spleen, relative to CARTs lacking fingolimod. Moreover, fingolimod-CART-mediated mRNA delivery induces peripheral blood T-cell depletion similar to free fingolimod. Thus, we show that functionalization of CARTs with a pharmacologically validated small molecule can increase transfection of a cellular population of interest while conferring some of the targeting properties of the conjugated small molecule to the CARTs.
View details for DOI 10.1021/acs.biomac.2c00469
View details for PubMedID 35748182
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Latency reversal plus natural killer cells diminish HIV reservoir in vivo.
Nature communications
1800; 13 (1): 121
Abstract
HIV is difficult to eradicate due to the persistence of a long-lived reservoir of latently infected cells. Previous studies have shown that natural killer cells are important to inhibiting HIV infection, but it is unclear whether the administration of natural killer cells can reduce rebound viremia when anti-retroviral therapy is discontinued. Here we show the administration of allogeneic human peripheral blood natural killer cells delays viral rebound following interruption of anti-retroviral therapy in humanized mice infected with HIV-1. Utilizing genetically barcoded virus technology, we show these natural killer cells efficiently reduced viral clones rebounding from latency. Moreover, a kick and kill strategy comprised of theprotein kinase C modulator and latency reversing agent SUW133 and allogeneic human peripheral blood natural killer cells during anti-retroviral therapy eliminated the viral reservoir in a subset of mice. Therefore, combinations utilizing latency reversal agents with targeted cellular killing agents may be an effective approach to eradicating the viral reservoir.
View details for DOI 10.1038/s41467-021-27647-0
View details for PubMedID 35013215
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An mRNA SARS-CoV-2 Vaccine Employing Charge-Altering Releasable Transporters with a TLR-9 Agonist Induces Neutralizing Antibodies and T Cell Memory.
ACS central science
2021; 7 (7): 1191-1204
Abstract
The SARS-CoV-2 pandemic has necessitated the rapid development of prophylactic vaccines. Two mRNA vaccines have been approved for emergency use by the FDA and have demonstrated extraordinary effectiveness. The success of these mRNA vaccines establishes the speed of development and therapeutic potential of mRNA. These authorized vaccines encode full-length versions of the SARS-CoV-2 spike protein. They are formulated with lipid nanoparticle (LNP) delivery vehicles that have inherent immunostimulatory properties. Different vaccination strategies and alternative mRNA delivery vehicles would be desirable to ensure flexibility of future generations of SARS-CoV-2 vaccines and the development of mRNA vaccines in general. Here, we report on the development of an alternative mRNA vaccine approach using a delivery vehicle called charge-altering releasable transporters (CARTs). Using these inherently nonimmunogenic vehicles, we can tailor the vaccine immunogenicity by inclusion of coformulated adjuvants such as oligodeoxynucleotides with CpG motifs (CpG-ODN). Mice vaccinated with the mRNA-CART vaccine developed therapeutically relevant levels of receptor binding domain (RBD)-specific neutralizing antibodies in both the circulation and in the lung bronchial fluids. In addition, vaccination elicited strong and long-lasting RBD-specific TH1 T cell responses including CD4+ and CD8+ T cell memory.
View details for DOI 10.1021/acscentsci.1c00361
View details for PubMedID 34341771
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Designed PKC-targeting bryostatin analogs modulate innate immunity and neuroinflammation.
Cell chemical biology
2021
Abstract
Neuroinflammation characterizes multiple neurologic diseases, including primary inflammatory conditions such as multiple sclerosis and classical neurodegenerative diseases. Aberrant activation of the innate immune system contributes to disease progression, but drugs modulating innate immunity, particularly within the central nervous system (CNS), are lacking. The CNS-penetrant natural product bryostatin-1 attenuates neuroinflammation by targeting innate myeloid cells. Supplies of natural bryostatin-1 are limited, but a recent scalable good manufacturing practice (GMP) synthesis has enabled access to it and its analogs (bryologs), the latter providing a path to more efficacious, better tolerated, and more accessible agents. Here, we show that multiple synthetically accessible bryologs replicate the anti-inflammatory effects of bryostatin-1 on innate immune cells in vitro, and a lead bryolog attenuates neuroinflammation in vivo, actions mechanistically dependent on protein kinase C (PKC) binding. Our findings identify bryologs as promising drug candidates for targeting innate immunity in neuroinflammation and create a platform for evaluation of synthetic PKC modulators in neuroinflammatory diseases.
View details for DOI 10.1016/j.chembiol.2020.12.015
View details for PubMedID 33472023
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In vivo targeting of E. coli with vancomycin-arginine.
Antimicrobial agents and chemotherapy
2021
Abstract
The ability of vancomycin-arginine (V-r) to extend the spectrum of activity of glycopeptides to gram-negative bacteria was investigated. Its MIC towards E. coli including β-lactamase expressing Ambler classes A, B, and D was 8-16μg/ml. Addition of 8×MIC V-r to E. coli was acutely bactericidal and associated with a low frequency of resistance (< 2.3×10-10). In vivo, V-r markedly reduced E. coli burden by >7 log10 CFU/g in a thigh muscle model. These data warrant further development of V-r in combatting E. coli, including resistant forms.
View details for DOI 10.1128/AAC.02416-20
View details for PubMedID 33468474
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Tracking HIV Rebound following Latency Reversal Using Barcoded HIV.
Cell reports. Medicine
2020; 1 (9): 100162
Abstract
HIV latency prevents cure of infection with antiretroviral therapy (ART) alone. One strategy for eliminating latently infected cells involves the induction of viral protein expression via latency-reversing agents (LRAs), allowing killing of host cells by viral cytopathic effects or immune effector mechanisms. Here, we combine a barcoded HIV approach and a humanized mouse model to study the effects of a designed, synthetic protein kinase C modulating LRA on HIV rebound. We show that administration of this compound during ART results in a delay in rebound once ART is stopped. Furthermore, the rebounding virus appears composed of a smaller number of unique barcoded viruses than occurs in control-treated animals, suggesting that some reservoir cells that would have contributed virus to the rebound process are eliminated by LRA administration. These data support the use of barcoded virus to study rebound and suggest that LRAs may be useful in HIV cure efforts.
View details for DOI 10.1016/j.xcrm.2020.100162
View details for PubMedID 33377133
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Function-Oriented Synthesis: Design, Synthesis, and Evaluation of Highly Simplified Bryostatin Analogues.
The Journal of organic chemistry
2020
Abstract
Using a function-oriented synthesis strategy, we designed, synthesized, and evaluated the simplest bryostatin 1 analogues reported to date, in which bryostatin's A- and B-rings are replaced by a glutarate linker. These analogues, one without and one with a C26-methyl group, exhibit remarkably different protein kinase C (PKC) isoform affinities. The former exhibited bryostatin-like binding to several PKC isoforms with Ki's < 5 nM, while the latter exhibited PKC affinities that were up to 180-fold less potent. The analogue with bryostatin-like PKC affinities also exhibited bryostatin-like PKC translocation kinetics in vitro, indicating rapid cell permeation and engagement of its PKC target. This study exemplifies the power of function-oriented synthesis in reducing structural complexity by activity-informed design, thus enhancing synthetic accessibility, while still maintaining function (biological activity), collectively providing new leads for addressing the growing list of therapeutic indications exhibited by PKC modulators.
View details for DOI 10.1021/acs.joc.0c01988
View details for PubMedID 33200928
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In Situ Detection of Endogenous HIV Activation by Dynamic Nuclear Polarization NMR and Flow Cytometry.
International journal of molecular sciences
2020; 21 (13)
Abstract
We demonstrate for the first time in-cell dynamic nuclear polarization (DNP) in conjunction with flow cytometry sorting to address the cellular heterogeneity of in-cell samples. Utilizing a green fluorescent protein (GFP) reporter of HIV reactivation, we correlate increased 15N resonance intensity with cytokine-driven HIV reactivation in a human cell line model of HIV latency. As few as 10% GFP+ cells could be detected by DNP nuclear magnetic resonance (NMR). The inclusion of flow cytometric sorting of GFP+ cells prior to analysis by DNP-NMR further boosted signal detection through increased cellular homogeneity with respect to GFP expression. As few as 3.6 million 15N-labeled GFP+ cells could be readily detected with DNP-NMR. Importantly, cell sorting allowed for the comparison of cytokine-treated GFP+ and GFP- cells in a batch-consistent way. This provides an avenue for normalizing NMR spectral contributions from background cellular processes following treatment with cellular modulators. We also demonstrate the remarkable stability of AMUPol (a nitroxide biradical) in Jurkat T cells and achieved in-cell enhancements of 46 with 10 mM AMUPol, providing an excellent model system for further in-cell DNP-NMR studies. This represents an important contribution to improving in-cell methods for the study of endogenously expressed proteins by DNP-NMR.
View details for DOI 10.3390/ijms21134649
View details for PubMedID 32629894
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Prodrugs of PKC modulators show enhanced HIV latency reversal and an expanded therapeutic window.
Proceedings of the National Academy of Sciences of the United States of America
2020
Abstract
AIDS is a pandemic disease caused by HIV that affects 37 million people worldwide. Current antiretroviral therapy slows disease progression but does not eliminate latently infected cells, which resupply active virus, thus necessitating lifelong treatment with associated compliance, cost, and chemoexposure issues. Latency-reversing agents (LRAs) activate these cells, allowing for their potential clearance, thus presenting a strategy to eradicate the infection. Protein kinase C (PKC) modulators-including prostratin, ingenol esters, bryostatin, and their analogs-are potent LRAs in various stages of development for several clinical indications. While LRAs are promising, a major challenge associated with their clinical use is sustaining therapeutically meaningful levels of the active agent while minimizing side effects. Here we describe a strategy to address this problem based on LRA prodrugs, designed for controllable release of the active LRA after a single injection. As intended, these prodrugs exhibit comparable or superior in vitro activity relative to the parent compounds. Selected compounds induced higher in vivo expression of CD69, an activation biomarker, and, by releasing free agent over time, significantly improved tolerability when compared to the parent LRAs. More generally, selected prodrugs of PKC modulators avoid the bolus toxicities of the parent drug and exhibit greater efficacy and expanded tolerability, thereby addressing a longstanding objective for many clinical applications.
View details for DOI 10.1073/pnas.1919408117
View details for PubMedID 32371485
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Synthesis and evaluation of designed PKC modulators for enhanced cancer immunotherapy.
Nature communications
2020; 11 (1): 1879
Abstract
Bryostatin 1 is a marine natural product under investigation for HIV/AIDS eradication, the treatment of neurological disorders, and enhanced CAR T/NK cell immunotherapy. Despite its promising activity, bryostatin 1 is neither evolved nor optimized for the treatment of human disease. Here we report the design, synthesis, and biological evaluation of several close-in analogs of bryostatin 1. Using a function-oriented synthesis approach, we synthesize a series of bryostatin analogs designed to maintain affinity for bryostatin's target protein kinase C (PKC) while enabling exploration of their divergent biological functions. Our late-stage diversification strategy provides efficient access to a library of bryostatin analogs, which per our design retain affinity for PKC but exhibit variable PKC translocation kinetics. We further demonstrate that select analogs potently increase cell surface expression of CD22, a promising CAR T cell target for the treatment of leukemias, highlighting the clinical potential of bryostatin analogs for enhancing targeted immunotherapies.
View details for DOI 10.1038/s41467-020-15742-7
View details for PubMedID 32312992
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Synthesis and mechanistic investigations of pH-responsive cationic poly(aminoester)s
CHEMICAL SCIENCE
2020; 11 (11): 2951–66
View details for DOI 10.1039/c9sc05267d
View details for Web of Science ID 000521247400006
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Clinical Correlates of Human Immunodeficiency Virus-1 (HIV-1) DNA and Inducible HIV-1 RNA Reservoirs in Peripheral Blood in Children With Perinatally Acquired HIV-1 Infection With Sustained Virologic Suppression for at Least 5 Years
CLINICAL INFECTIOUS DISEASES
2020; 70 (5): 859–66
View details for DOI 10.1093/cid/ciz251
View details for Web of Science ID 000520551800023
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Synthesis and mechanistic investigations of pH-responsive cationic poly(aminoester)s.
Chemical science
2020; 11 (11): 2951-2966
Abstract
The synthesis and degradation mechanisms of a class of pH-sensitive, rapidly degrading cationic poly(α-aminoester)s are described. These reactive, cationic polymers are stable at low pH in water, but undergo a fast and selective degradation at higher pH to liberate neutral diketopiperazines. Related materials incorporating oligo(α-amino ester)s have been shown to be effective gene delivery agents, as the charge-altering degradative behavior facilitates the delivery and release of mRNA and other nucleic acids in vitro and in vivo. Herein, we report detailed studies of the structural and environmental factors that lead to these rapid and selective degradation processes in aqueous buffers. At neutral pH, poly(α-aminoester)s derived from N-hydroxyethylglycine degrade selectively by a mechanism involving sequential 1,5- and 1,6-O→N acyl shifts to generate bis(N-hydroxyethyl) diketopiperazine. A family of structurally related cationic poly(aminoester)s was generated to study the structural influences on the degradation mechanism, product distribution, and pH dependence of the rate of degradation. The kinetics and mechanism of the pH-induced degradations were investigated by 1H NMR, model reactions, and kinetic simulations. These results indicate that polyesters bearing α-ammonium groups and appropriately positioned N-hydroxyethyl substituents are readily cleaved (by intramolecular attack) or hydrolyzed, representing dynamic "dual function" materials that are initially polycationic and transform with changing environment to neutral products.
View details for DOI 10.1039/c9sc05267d
View details for PubMedID 34122796
View details for PubMedCentralID PMC8157522
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Reversible RNA acylation for control of CRISPR-Cas9 gene editing
CHEMICAL SCIENCE
2020; 11 (4): 1011–16
View details for DOI 10.1039/c9sc03639c
View details for Web of Science ID 000510929600008
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Charge-altering releasable transporters enable phenotypic manipulation of natural killer cells for cancer immunotherapy.
Blood advances
2020; 4 (17): 4244–55
Abstract
Chimeric antigen receptor (CAR) natural killer (NK) cells are an emerging cell therapy with promising results in oncology trials. However, primary human NK cells are difficult to transfect, hampering both mechanistic studies and clinical applications of NK cells. Currently, NK cell CAR modification relies on viral vectors or cell activation. The former raises cost and tolerability issues, while the latter alters NK cell biology. Here, we report that readily synthesized and inexpensive nonviral charge-altering releasable transporters (CARTs) efficiently transfect primary human NK cells with messenger RNA without relying on NK cell activation. Compared with electroporation, CARTs transfect NK cells more efficiently, better preserve cell viability, and cause minimal reconfiguration of NK cell phenotype and function. We use CARTs to generate cytotoxic primary anti-CD19 CAR NK cells, demonstrating this technology can drive clinical applications of NK cells. To our knowledge, CARTs represent the first efficacious transfection technique for resting primary human NK cells that preserves NK cell phenotype and can enable new biological discoveries and therapeutic applications of this understudied lymphocyte subset.
View details for DOI 10.1182/bloodadvances.2020002355
View details for PubMedID 32898247
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Bryostatin 1 Promotes Synaptogenesis and Reduces Dendritic Spine Density in Cortical Cultures through a PKC-Dependent Mechanism.
ACS chemical neuroscience
2020
Abstract
The marine natural product bryostatin 1 has demonstrated procognitive and antidepressant effects in animals and has been entered into human clinical trials for treating Alzheimer's disease (AD). The ability of bryostatin 1 to enhance learning and memory has largely been attributed to its effects on the structure and function of hippocampal neurons. However, relatively little is known about how bryostatin 1 influences the morphology of cortical neurons, key cells that also support learning and memory processes and are negatively impacted in AD. Here, we use a combination of carefully designed chemical probes and pharmacological inhibitors to establish that bryostatin 1 increases cortical synaptogenesis while decreasing dendritic spine density in a protein kinase C (PKC)-dependent manner. The effects of bryostatin 1 on cortical neurons are distinct from those induced by neural plasticity-promoting psychoplastogens such as ketamine. Compounds capable of increasing synaptic density with concomitant loss of immature dendritic spines may represent a unique pharmacological strategy for enhancing memory by improving signal-to-noise ratio in the central nervous system.
View details for DOI 10.1021/acschemneuro.0c00175
View details for PubMedID 32437156
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Reversible RNA acylation for control of CRISPR-Cas9 gene editing.
Chemical science
2019; 11 (4): 1011-1016
Abstract
We report the development of post-transcriptional chemical methods that enable control over CRISPR-Cas9 gene editing activity both in in vitro assays and in living cells. We show that an azide-substituted acyl imidazole reagent (NAI-N3) efficiently acylates CRISPR single guide RNAs (sgRNAs) in 20 minutes in buffer. Poly-acylated ("cloaked") sgRNA was completely inactive in DNA cleavage with Cas9 in vitro, and activity was quantitatively restored after phosphine treatment. Delivery of cloaked sgRNA and Cas9 mRNA into HeLa cells was enabled by the use of charge-altering releasable transporters (CARTs), which outperformed commercial transfection reagents in transfecting sgRNA co-complexed with Cas9 encoding functional mRNA. Genomic DNA cleavage in the cells by CRISPR-Cas9 was efficiently restored after treatment with phosphine to remove the blocking acyl groups. Our results highlight the utility of reversible RNA acylation as a novel method for temporal control of genome-editing function.
View details for DOI 10.1039/c9sc03639c
View details for PubMedID 34084356
View details for PubMedCentralID PMC8145180
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Synthesis of Modified Nucleoside Oligophosphates Simplified: Fast, Pure, and Protecting Group Free.
Journal of the American Chemical Society
2019
Abstract
Phosphoramidite analogues of modified cyclotriphosphates provide a general and step-economical synthesis of nucleoside triphosphates and analogues on scale without the need for protecting groups. These reagents enable rapid access to pure nucleoside oligophosphates and a range of other analogues that were previously difficult to obtain (e.g., NH, CH2, CCl2, and CF2 replacements for O, phosphono- and phosphoimidazolides, -morpholidates, -azidates, and -fluoridates). DFT calculations demonstrate that the selectivity of the cyclotriphosphate opening reactions proceeds via an in-line substitution mechanism that displaces the least charged leaving group.
View details for DOI 10.1021/jacs.9b08273
View details for PubMedID 31512870
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Impact of Treatment Interruption on HIV Reservoirs and Lymphocyte Subsets in Individuals Who Initiated Antiretroviral Therapy During the Early Phase of Infection
JOURNAL OF INFECTIOUS DISEASES
2019; 220 (2): 270–74
View details for DOI 10.1093/infdis/jiz100
View details for Web of Science ID 000482357500013
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Oligo(serine ester) Charge-Altering Releasable Transporters: Organocatalytic Ring-Opening Polymerization and their Use for in Vitro and in Vivo mRNA Delivery
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2019; 141 (21): 8416–21
View details for DOI 10.1021/jacs.9b03154
View details for Web of Science ID 000470034500006
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Local Delivery of Ox40l, Cd80, and Cd86 mRNA Kindles Global Anticancer Immunity
CANCER RESEARCH
2019; 79 (7): 1624–34
View details for DOI 10.1158/0008-5472.CAN-18-2867
View details for Web of Science ID 000463005700033
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Therapeutic function through synthesis-informed design: Approaches to HIV/AIDS eradication, Alzheimer's disease, and enhanced cancer immuno-therapy
AMER CHEMICAL SOC. 2019
View details for Web of Science ID 000478861203408
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Clinical correlates of HIV-1 DNA and inducible HIV-1 RNA reservoirs in peripheral blood in children with perinatally acquired HIV-1 infection with sustained virologic suppression for at least 5 years.
Clinical infectious diseases : an official publication of the Infectious Diseases Society of America
2019
Abstract
BACKGROUND: The Early Pediatric Initiation Canada Child Cure Cohort (EPIC4) study is a prospective, multicenter Canadian cohort study investigating HIV-1 reservoirs, chronic inflammation and immune responses in children with perinatally-acquired HIV-1 infection. The focus of this report is HIV-1 reservoirs and correlates in peripheral blood of children who achieved sustained virologic suppression (SVS) ≥5 years.METHODS: HIV-1 reservoirs were determined by measuring HIV-1 DNA in peripheral blood mononuclear cells (PBMC) and inducible cell-free HIV-1 RNA in CD4+ T cells by a prostratin analogue stimulation assay. HIV serology was quantified by signal to cut-off ratio (S/CO).RESULTS: Of 227 enrolled, 69 had SVS ≥5 years. HIV-1 DNA, inducible cell-free HIV-1 RNA and S/CO correlated directly with age of effective cART initiation (p<0.001, p=0.036, p<0.001) and age when SVS was achieved (p=0.002, p=0.038, p<0.001) and inversely with proportion of life on effective cART (p<0.001, p=0.01, p<0.001) and proportion of life with SVS (p<0.001, p=0.079, p<0.001). Inducible cell-free HIV-1 RNA correlated with HIV-1 DNA, most particularly in children with SVS, without virologic blips, achieved with first cART regimen initiated prior to 6 months of age (rho=0.74, p=0.037) or later (rho=0.87, p<0.001). S/CO correlated with HIV-1 DNA (p=0.003), but less so with inducible cell-free HIV-1 RNA (p=0.09).CONCLUSIONS: The prostratin analogue stimulation assay, with its lower blood volume requirement, could be a valuable method for evaluating inducible HIV-1 reservoirs in children. Standard commercial HIV serology may be a practical initial indirect measure of reservoir size in peripheral blood of children with perinatally-acquired HIV-1 infection.
View details for PubMedID 30919879
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A Phosphoramidite Analogue of Cyclotriphosphate Enables Iterative Polyphosphorylations
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2019; 58 (12): 3928-3933
View details for DOI 10.1002/anie.201814366
View details for Web of Science ID 000462680700044
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Impact of treatment interruption on HIV reservoirs and lymphocyte subsets in individuals who had initiated antiretroviral therapy during the early phase of infection.
The Journal of infectious diseases
2019
Abstract
Therapeutic strategies for achieving sustained virologic remission are being explored in HIV-infected individuals who began antiretroviral therapy (ART) during the early phase of infection. In the evaluation of such therapies, clinical protocols should include analytical treatment interruption (ATI); however, the immunologic and virologic impact of ATI in early-treated individuals has not been fully delineated. We demonstrate that ATI causes neither expansion of HIV reservoirs nor immunologic abnormalities following reinitiation of ART. Our findings support the use of ATI to determine whether sustained virologic remission has been achieved in clinical trials of individuals who initiated ART early in HIV infection.
View details for PubMedID 30840763
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Local delivery of OX40L, CD80, and CD86 mRNA kindles global anti-cancer immunity.
Cancer research
2019
Abstract
Localized expression of effector molecules can initiate anti-tumor responses through engagement of specific receptors on target cells in the tumor microenvironment. These locally induced responses may also have a systemic effect, clearing additional tumors throughout the body. In this study, to evoke systemic anti-tumor responses, we utilized charge-altering releasable transporters (CART) for local intratumoral delivery of mRNA coding for co-stimulatory and immune-modulating factors. Intratumoral injection of the CART-mRNA complexes resulted in mRNA expression at the site of administration, transfecting a substantial proportion of tumor-infiltrating dendritic cells, macrophages, and T cells in addition to the tumor cells, resulting in a local anti-tumor effect. Using a two-tumor model, we further show that mRNA therapy locally administered to one tumor stimulated a systemic anti-tumor response, curing both tumors. The combination of OX40L-, CD80-, and CD86-encoding mRNA resulted in the local upregulation of pro-inflammatory cytokines, robust local T cell activation, and migration of immune cells to local draining lymph node or to an anatomically distant tumor. This approach delayed tumor growth, facilitated tumor regression, and cured tumors in both A20 and CT26 tumor models. These results highlight mRNA-CART therapy as a viable approach to induce systemic anti-tumor immunity from a single localized injection.
View details for PubMedID 30692215
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A Phosphoramidite Analogue of Cyclotriphosphate Enables Iterative Polyphosphorylations.
Angewandte Chemie (International ed. in English)
2019
Abstract
An iterative polyphosphorylation approach is described, which is based on a phosphoramidite (P-amidite) derived reagent (c-PyPA) obtained from the cyclization of pyrophosphate with a reactive diisopropylaminodichlorophosphine. This type of reagent is unprecedented as it represents a reactive P-amidite without protecting groups. The reagent proved to be stable in solution over several weeks. Its utility is described in the context of iterative monodirectional and bidirectional polyphosphorylations. The ensuing functionalized cyclotriphosphate can be opened with a variety of nucleophiles providing ready access to diverse functionalized polyphosphate chains of defined length with several tags, including both P-N and P-O labels. Their interaction with exo- and endopolyphosphatases is described.
View details for PubMedID 30681761
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Oligo(serine ester) Charge-Altering Releasable Transporters: Organocatalytic Ring-Opening Polymerization and their Use for in Vitro and in Vivo mRNA Delivery.
Journal of the American Chemical Society
2019
Abstract
RNA technology is transforming life science research and medicine, but many applications are limited by the accessibility, cost, efficacy, and tolerability of delivery systems. Here we report the first members of a new class of dynamic RNA delivery vectors, oligo(serine ester)-based charge-altering releasable transporters (Ser-CARTs). Composed of lipid-containing oligocarbonates and cationic oligo(serine esters), Ser-CARTs are readily prepared (one flask) by a mild ring-opening polymerization using thiourea anions and, upon simple mixing with mRNA, readily form complexes that degrade to neutral serine-based products, efficiently releasing their mRNA cargo. mRNA/Ser-CART transfection efficiencies of >95% are achieved in vitro. Intramuscular or intravenous (iv) injections of mRNA/Ser-CARTs into living mice result in in vivo expression of a luciferase reporter protein, with spleen localization observed after iv injection.
View details for PubMedID 31083999
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Vancomycin-Arginine Conjugate Inhibits Growth of Carbapenem-Resistant E. coli and Targets Cell-Wall Synthesis.
ACS chemical biology
2019
Abstract
The emergence of multi-drug-resistant Gram-negative bacteria, including carbapenem-resistant Enterobacteriaceae, is a major health problem that necessitates the development of new antibiotics. Vancomycin inhibits cell-wall synthesis in Gram-positive bacteria but is generally ineffective against Gram-negative bacteria and is unable to penetrate the outer membrane barrier. In an effort to determine whether vancomycin and other antibiotics effective against Gram-positive bacteria could, through modification, be rendered effective against Gram-negative bacteria, we discovered that the covalent attachment of a single arginine to vancomycin yielded conjugates with order-of-magnitude improvements in activity against Gram-negative bacteria, including pathogenic E. coli. The vancomycin-arginine conjugate (V-R) exhibited efficacy against actively growing bacteria, induced the loss of rod cellular morphology, and resulted in the intracellular accumulation of peptidoglycan precursors, all consistent with cell-wall synthesis disruption as its mechanism of action. Membrane permeabilization studies demonstrated an enhanced outer membrane permeability of V-R as compared with vancomycin. The conjugate exhibited no mammalian cell toxicity or hemolytic activity in MTT and hemolysis assays. Our study introduces a new vancomycin derivative effective against Gram-negative bacteria and underscores the broader potential of generating new antibiotics through combined mode-of-action and synthesis-informed design studies.
View details for DOI 10.1021/acschembio.9b00565
View details for PubMedID 31479234
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A Dual-Function Antibiotic-Transporter Conjugate Exhibits Superior Activity in Sterilizing MRSA Biofilms and Killing Persister Cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2018; 140 (47): 16140-16151
View details for DOI 10.1021/jacs.8b08711
View details for Web of Science ID 000451933100023
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Delivery of Inorganic Polyphosphate into Cells Using Amphipathic Oligocarbonate Transporters.
ACS central science
2018; 4 (10): 1394-1402
Abstract
Inorganic polyphosphate (polyP) is an often-overlooked biopolymer of phosphate residues present in living cells. PolyP is associated with many essential biological roles. Despite interest in polyP's function, most studies have been limited to extracellular or isolated protein experiments, as polyanionic polyP does not traverse the nonpolar membrane of cells. To address this problem, we developed a robust, readily employed method for polyP delivery using guanidinium-rich oligocarbonate transporters that electrostatically complex polyPs of multiple lengths, forming discrete nanoparticles that are resistant to phosphatase degradation and that readily enter multiple cell types. Fluorescently labeled polyPs have been monitored over time for subcellular localization and release from the transporter, with control over release rates achieved by modulating the transporter identity and the charge ratio of the electrostatic complexes. This general approach to polyP delivery enables the study of intracellular polyP signaling in a variety of applications.
View details for DOI 10.1021/acscentsci.8b00470
View details for PubMedID 30410977
View details for PubMedCentralID PMC6202642
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mRNA vaccination with charge-altering releasable transporters elicits human T cell responses and cures established tumors in mice
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2018; 115 (39): E9153–E9161
View details for DOI 10.1073/pnas.1810002115
View details for Web of Science ID 000445545200016
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mRNA vaccination with charge-altering releasable transporters elicits human T cell responses and cures established tumors in mice.
Proceedings of the National Academy of Sciences of the United States of America
2018
Abstract
In vivo delivery of antigen-encoding mRNA is a promising approach to personalized cancer treatment. The therapeutic efficacy of mRNA vaccines is contingent on safe and efficient gene delivery, biological stability of the mRNA, and the immunological properties of the vaccine. Here we describe the development and evaluation of a versatile and highly efficient mRNA vaccine-delivery system that employs charge-altering releasable transporters (CARTs) to deliver antigen-coding mRNA to antigen-presenting cells (APCs). We demonstrate in human peripheral blood mononuclear cells that CART vaccines can activate a robust antigen-specific immune response against mRNA-encoded viral epitopes. In an established mouse model, we demonstrate that CARTs preferentially target professional APCs in secondary lymphoid organs upon i.v. injections and target local APCs upon s.c. injection. Finally, we show that CARTs coformulated with mRNA and a Toll-like receptor ligand simultaneously transfect and activate target cells to generate an immune response that can treat and cure mice with large, established tumors.
View details for PubMedID 30201728
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Functional DNA Delivery Enabled by Lipid-Modified Charge-Altering Releasable Transporters (CARTs)
BIOMACROMOLECULES
2018; 19 (7): 2812–24
Abstract
Safe and effective DNA delivery systems are required to enable or enhance clinical strategies and research involving gene therapy and DNA vaccinations. To address this delivery problem, a series of charge-altering releasable transporters (CARTs) with varied lipid content were prepared and evaluated for plasmid DNA (pDNA) delivery into cultured cells. These lipid-modified CART co-oligomers were synthesized in only two steps via sequential organocatalytic ring-opening polymerization of lipid-containing cyclic carbonate monomers and morpholinone monomers. Lipid variations of the CARTs substantially impacted the delivery efficiency of pDNA, with oleyl- and linoleyl-based CARTs showing enhanced performance relative to the commercial transfection agent Lipofectamine 2000 (L2000). The best-performing oleyl CART was carried forward to study stable luciferase transfection with a Sleeping Beauty ( SB) transposon system. The oleyl CART outperformed the L2000 positive control with respect to stable transfection efficiency. CART-pDNA complexes represent a new DNA delivery system for research and clinical applications.
View details for DOI 10.1021/acs.biomac.8b00401
View details for Web of Science ID 000438470800044
View details for PubMedID 29727572
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Characterization of designed, synthetically accessible bryostatin analog HIV latency reversing agents
VIROLOGY
2018; 520: 83–93
Abstract
HIV latency in resting CD4+ T cell represents a key barrier preventing cure of the infection with antiretroviral drugs alone. Latency reversing agents (LRAs) can activate HIV expression in latently infected cells, potentially leading to their elimination through virus-mediated cytopathic effects, host immune responses, and/or therapeutic strategies targeting cells actively expressing virus. We have recently described several structurally simplified analogs of the PKC modulator LRA bryostatin (termed bryologs) designed to improve synthetic accessibility, tolerability in vivo, and efficacy in inducing HIV latency reversal. Here we report the comparative performance of lead bryologs, including their effects in reducing cell surface expression of HIV entry receptors, inducing proinflammatory cytokines, inhibiting short-term HIV replication, and synergizing with histone deacetylase inhibitors to reverse HIV latency. These data provide unique insights into structure-function relationships between A- and B-ring bryolog modifications and activities in primary cells, and suggest that bryologs represent promising leads for preclinical advancement.
View details for PubMedID 29800728
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Enhanced mRNA delivery into lymphocytes enabled by lipid-varied libraries of charge-altering releasable transporters.
Proceedings of the National Academy of Sciences of the United States of America
2018; 115 (26): E5859–E5866
Abstract
We report a strategy for generating a combinatorial library of oligonucleotide transporters with varied lipid domains and their use in the efficient transfection of lymphocytes with mRNA in vitro and in vivo. This library is based on amphiphilic charge-altering releasable transporters (CARTs) that contain a lipophilic block functionalized with various side-chain lipids and a polycationic alpha-amino ester mRNA-binding block that undergoes rearrangement to neutral small molecules, resulting in mRNA release. We show that certain binary mixtures of these lipid-varied CARTs provide up to a ninefold enhancement in mRNA translation in lymphocytes in vitro relative to either a single-lipid CART component alone or the commercial reagent Lipofectamine 2000, corresponding to a striking increase in percent transfection from 9-12% to 80%. Informed by the results with binary mixtures, we further show that CARTs consisting of optimized ratios of the two lead lipids incorporated into a single hybrid-lipid transporter molecule maintain the same delivery efficacy as the noncovalent mixture of two CARTs. The lead lipid CART mixtures and hybrid-lipid CARTs show enhanced lymphocyte transfection in primary T cells and in vivo in mice. This combinatorial approach for rapidly screening mRNA delivery vectors has provided lipid-varied CART mixtures and hybrid-lipid CARTs that exhibit significant improvement in mRNA delivery to lymphocytes, a finding of potentially broad value in research and clinical applications.
View details for PubMedID 29891683
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Enhanced mRNA delivery into lymphocytes enabled by lipid-varied libraries of charge-altering releasable transporters
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2018; 115 (26): E5859–E5866
View details for DOI 10.1073/pnas.1805358115
View details for Web of Science ID 000436245000007
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REDOR NMR Reveals Multiple Conformers for a Protein Kinase C Ligand in a Membrane Environment
ACS CENTRAL SCIENCE
2018; 4 (1): 89–96
Abstract
Bryostatin 1 (henceforth bryostatin) is in clinical trials for the treatment of Alzheimer's disease and for HIV/AIDS eradication. It is also a preclinical lead for cancer immunotherapy and other therapeutic indications. Yet nothing is known about the conformation of bryostatin bound to its protein kinase C (PKC) target in a membrane microenvironment. As a result, efforts to design more efficacious, better tolerated, or more synthetically accessible ligands have been limited to structures that do not include PKC or membrane effects known to influence PKC-ligand binding. This problem extends more generally to many membrane-associated proteins in the human proteome. Here, we use rotational-echo double-resonance (REDOR) solid-state NMR to determine the conformations of PKC modulators bound to the PKCδ-C1b domain in the presence of phospholipid vesicles. The conformationally limited PKC modulator phorbol diacetate (PDAc) is used as an initial test substrate. While unanticipated partitioning of PDAc between an immobilized protein-bound state and a mobile state in the phospholipid assembly was observed, a single conformation in the bound state was identified. In striking contrast, a bryostatin analogue (bryolog) was found to exist exclusively in a protein-bound state, but adopts a distribution of conformations as defined by three independent distance measurements. The detection of multiple PKCδ-C1b-bound bryolog conformers in a functionally relevant phospholipid complex reveals the inherent dynamic nature of cellular systems that is not captured with single-conformation static structures. These results indicate that binding, selectivity, and function of PKC modulators, as well as the design of new modulators, are best addressed using a dynamic multistate model, an analysis potentially applicable to other membrane-associated proteins.
View details for PubMedID 29392180
View details for PubMedCentralID PMC5785774
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Delivery of Inorganic Polyphosphate into Cells Using Amphipathic Oligocarbonate Transporters
ACS Cent. Sci.
2018
View details for DOI 10.1021/acscentsci.8b00470
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Enantioselective Cobalt-catalysed Transformations Foreword
ENANTIOSELECTIVE COBALT-CATALYSED TRANSFORMATIONS
2018; 35: VII-VIII
View details for Web of Science ID 000562013700001
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A dual function antibiotic-transporter conjugate exhibits superior activity in sterilizing MRSA biofilms and killing persister cells.
Journal of the American Chemical Society
2018
Abstract
New strategies are urgently needed to target MRSA, a major global health problem and the leading cause of mortality from antibiotic-resistant infections in many countries. Here we report a general approach to this problem exemplified by the design and synthesis of a vancomycin-D-octaarginine conjugate (V-r8) and investigation of its efficacy in addressing antibiotic-insensitive bacterial populations. V-r8 eradicated MRSA biofilm and persister cells in vitro, outperforming vancomycin by orders of magnitude. It also eliminated 97% of biofilm-associated MRSA in a murine wound infection model and displayed no acute dermal toxicity. This new dual function conjugate displays enhanced cellular accumulation and membrane perturba-tion as compared to vancomycin. Based on its rapid and potent activity against biofilm and persister cells, V-r8 is a promis-ing agent against clinical MRSA infections.
View details for PubMedID 30388366
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Molecular dynamics simulations reveal ligand-controlled positioning of a peripheral protein complex in membranes.
Nature communications
2017; 8 (1): 6-?
Abstract
Bryostatin is in clinical trials for Alzheimer's disease, cancer, and HIV/AIDS eradication. It binds to protein kinase C competitively with diacylglycerol, the endogenous protein kinase C regulator, and plant-derived phorbol esters, but each ligand induces different activities. Determination of the structural origin for these differing activities by X-ray analysis has not succeeded due to difficulties in co-crystallizing protein kinase C with relevant ligands. More importantly, static, crystal-lattice bound complexes do not address the influence of the membrane on the structure and dynamics of membrane-associated proteins. To address this general problem, we performed long-timescale (400-500 µs aggregate) all-atom molecular dynamics simulations of protein kinase C-ligand-membrane complexes and observed that different protein kinase C activators differentially position the complex in the membrane due in part to their differing interactions with waters at the membrane inner leaf. These new findings enable new strategies for the design of simpler, more effective protein kinase C analogs and could also prove relevant to other peripheral protein complexes.Natural supplies of bryostatin, a compound in clinical trials for Alzheimer's disease, cancer, and HIV, are scarce. Here, the authors perform molecular dynamics simulations to understand how bryostatin interacts with membrane-bound protein kinase C, offering insights for the design of bryostatin analogs.
View details for DOI 10.1038/s41467-016-0015-8
View details for PubMedID 28232750
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Gilbert Stork (1921-2017) Chemist who revolutionized molecular synthesis
NATURE
2017; 551 (7682): 566
View details for PubMedID 29189811
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Ynol Ethers as Ketene Equivalents in Rhodium-Catalyzed Intermolecular [5+2] Cycloaddition Reactions
ORGANIC LETTERS
2017; 19 (21): 5810–13
Abstract
The previously unexplored metal-catalyzed [5 + 2] cycloadditions of vinylcyclopropanes (VCPs) and electron-rich alkynes (ynol ethers) have been found to provide a highly efficient, direct route to dioxygenated seven-membered rings, a common feature of numerous natural and non-natural targets and building blocks for synthesis. The reactions proceed in high yield at room temperature and tolerate a broad range of functionalities. Substituted VCPs were found to react with high regioselectivity.
View details for PubMedID 29034684
View details for PubMedCentralID PMC5833981
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Retrosynthetic Reaction Prediction Using Neural Sequence-to-Sequence Models
ACS CENTRAL SCIENCE
2017; 3 (10): 1103–13
Abstract
We describe a fully data driven model that learns to perform a retrosynthetic reaction prediction task, which is treated as a sequence-to-sequence mapping problem. The end-to-end trained model has an encoder-decoder architecture that consists of two recurrent neural networks, which has previously shown great success in solving other sequence-to-sequence prediction tasks such as machine translation. The model is trained on 50,000 experimental reaction examples from the United States patent literature, which span 10 broad reaction types that are commonly used by medicinal chemists. We find that our model performs comparably with a rule-based expert system baseline model, and also overcomes certain limitations associated with rule-based expert systems and with any machine learning approach that contains a rule-based expert system component. Our model provides an important first step toward solving the challenging problem of computational retrosynthetic analysis.
View details for PubMedID 29104927
View details for PubMedCentralID PMC5658761
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Scalable synthesis of bryostatin 1 and analogs, adjuvant leads against latent HIV
SCIENCE
2017; 358 (6360): 218–22
Abstract
Bryostatin 1 is an exceedingly scarce marine-derived natural product that is in clinical development directed at HIV/AIDS eradication, cancer immunotherapy, and the treatment of Alzheimer's disease. Despite this unique portfolio of indications, its availability has been limited and variable, thus impeding research and clinical studies. Here, we report a total synthesis of bryostatin 1 that proceeds in 29 total steps (19 in the longest linear sequence, >80% average yield per step), collectively produces grams of material, and can be scaled to meet clinical needs (~20 grams per year). This practical solution to the bryostatin supply problem also opens broad, facile, and efficient access to derivatives and potentially superior analogs.
View details for PubMedID 29026042
View details for PubMedCentralID PMC5714505
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Bryostatin and its synthetic analog, picolog rescue dermal fibroblasts from prolonged stress and contribute to survival and rejuvenation of human skin equivalents.
Journal of cellular physiology
2017
Abstract
Skin health is associated with the day-to-day activity of fibroblasts. The primary function of fibroblasts is to synthesize structural proteins, such as collagen, extracellular matrix proteins, and other proteins that support the structural integrity of the skin and are associated with younger, firmer, and more elastic skin that is better able to resist and recover from injury. At sub-nanomolar concentrations (0.03-0.3 nM), bryostatin-1 and its synthetic analog, picolog (0.1-10 nM) sustained the survival and activation of human dermal fibroblasts cultured under the stressful condition of prolonged serum deprivation. Bryostatin-1 treatment stabilized human skin equivalents (HSEs), a bioengineered combination of primary human skin cells (keratinocytes and dermal fibroblasts) on an extracellular matrix composed of mainly collagen. Fibroblasts activated by bryostatin-1 protected the structural integrity of HSEs. Bryostatin-1 and picolog prolonged activation of Erk in fibroblasts to promote cell survival. Chronic stress promotes the progression of apoptosis. Dermal fibroblasts constitutively express all components of Fas associated apoptosis, including caspase-8, an initiator enzyme of apoptosis. Prolong bryostatin-1 treatment reduced apoptosis by decreasing caspase-8 and protected dermal fibroblasts. Our data suggest that bryostatin-1 and picolog could be useful in anti-aging skincare, and could have applications in tissue engineering and regenerative medicine. This article is protected by copyright. All rights reserved.
View details for DOI 10.1002/jcp.26043
View details for PubMedID 28590053
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Charge-Altering Releasable Transporters (CARTs) for the delivery and release of messenger RNA in living animals
AMER CHEMICAL SOC. 2017
View details for Web of Science ID 000430569108182
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Charge-altering releasable transporters (CARTs) for the delivery and release of mRNA in living animals
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2017; 114 (4): E448-E456
Abstract
Functional delivery of mRNA to tissues in the body is key to implementing fundamentally new and potentially transformative strategies for vaccination, protein replacement therapy, and genome editing, collectively affecting approaches for the prevention, detection, and treatment of disease. Broadly applicable tools for the efficient delivery of mRNA into cultured cells would advance many areas of research, and effective and safe in vivo mRNA delivery could fundamentally transform clinical practice. Here we report the step-economical synthesis and evaluation of a tunable and effective class of synthetic biodegradable materials: charge-altering releasable transporters (CARTs) for mRNA delivery into cells. CARTs are structurally unique and operate through an unprecedented mechanism, serving initially as oligo(α-amino ester) cations that complex, protect, and deliver mRNA and then change physical properties through a degradative, charge-neutralizing intramolecular rearrangement, leading to intracellular release of functional mRNA and highly efficient protein translation. With demonstrated utility in both cultured cells and animals, this mRNA delivery technology should be broadly applicable to numerous research and therapeutic applications.
View details for DOI 10.1073/pnas.1614193114
View details for Web of Science ID 000392597000002
View details for PubMedID 28069945
View details for PubMedCentralID PMC5278438
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Vault Nanoparticles: Chemical Modifications for Imaging and Enhanced Delivery
ACS NANO
2017; 11 (1): 872-881
Abstract
Vault nanoparticles represent promising vehicles for drug and probe delivery. Innately found within human cells, vaults are stable, biocompatible nanocapsules possessing an internal volume that can encapsulate hundreds to thousands of molecules. They can also be targeted. Unlike most nanoparticles, vaults are nonimmunogenic and monodispersed and can be rapidly produced in insect cells. Efforts to create vaults with modified properties have been, to date, almost entirely limited to recombinant bioengineering approaches. Here we report a systematic chemical study of covalent vault modifications, directed at tuning vault properties for research and clinical applications, such as imaging, targeted delivery, and enhanced cellular uptake. As supra-macromolecular structures, vaults contain thousands of derivatizable amino acid side chains. This study is focused on establishing the comparative selectivity and efficiency of chemically modifying vault lysine and cysteine residues, using Michael additions, nucleophilic substitutions, and disulfide exchange reactions. We also report a strategy that converts the more abundant vault lysine residues to readily functionalizable thiol terminated side chains through treatment with 2-iminothiolane (Traut's reagent). These studies provide a method to doubly modify vaults with cell penetrating peptides and imaging agents, allowing for in vitro studies on their enhanced uptake into cells.
View details for DOI 10.1021/acsnano.6b07440
View details for Web of Science ID 000392886500091
View details for PubMedID 28029784
View details for PubMedCentralID PMC5372831
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Combinations of isoform-targeted histone deacetylase inhibitors and bryostatin analogues display remarkable potency to activate latent HIV without global T-cell activation.
Scientific reports
2017; 7 (1): 7456
Abstract
Current antiretroviral therapy (ART) for HIV/AIDS slows disease progression by reducing viral loads and increasing CD4 counts. Yet ART is not curative due to the persistence of CD4+ T-cell proviral reservoirs that chronically resupply active virus. Elimination of these reservoirs through the administration of synergistic combinations of latency reversing agents (LRAs), such as histone deacetylase (HDAC) inhibitors and protein kinase C (PKC) modulators, provides a promising strategy to reduce if not eradicate the viral reservoir. Here, we demonstrate that largazole and its analogues are isoform-targeted histone deacetylase inhibitors and potent LRAs. Significantly, these isoform-targeted HDAC inhibitors synergize with PKC modulators, namely bryostatin-1 analogues (bryologs). Implementation of this unprecedented LRA combination induces HIV-1 reactivation to unparalleled levels and avoids global T-cell activation within resting CD4+ T-cells.
View details for PubMedID 28785069
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In vivo activation of latent HIV with a synthetic bryostatin analog effects both latent cell "kick" and "kill" in strategy for virus eradication.
PLoS pathogens
2017; 13 (9): e1006575
Abstract
The ability of HIV to establish a long-lived latent infection within resting CD4+ T cells leads to persistence and episodic resupply of the virus in patients treated with antiretroviral therapy (ART), thereby preventing eradication of the disease. Protein kinase C (PKC) modulators such as bryostatin 1 can activate these latently infected cells, potentially leading to their elimination by virus-mediated cytopathic effects, the host's immune response and/or therapeutic strategies targeting cells actively expressing virus. While research in this area has focused heavily on naturally-occurring PKC modulators, their study has been hampered by their limited and variable availability, and equally significantly by sub-optimal activity and in vivo tolerability. Here we show that a designed, synthetically-accessible analog of bryostatin 1 is better-tolerated in vivo when compared with the naturally-occurring product and potently induces HIV expression from latency in humanized BLT mice, a proven and important model for studying HIV persistence and pathogenesis in vivo. Importantly, this induction of virus expression causes some of the newly HIV-expressing cells to die. Thus, designed, synthetically-accessible, tunable, and efficacious bryostatin analogs can mediate both a "kick" and "kill" response in latently-infected cells and exhibit improved tolerability, therefore showing unique promise as clinical adjuvants for HIV eradication.
View details for PubMedID 28934369
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Comparative analysis of the anti-chikungunya virus activity of novel bryostatin analogs confirms the existence of a PKC-independent mechanism.
Biochemical pharmacology
2016; 120: 15-21
Abstract
Previously, we reported that salicylate-based analogs of bryostatin protect cells from chikungunya virus (CHIKV)-induced cell death. Interestingly, 'capping' the hydroxyl group at C26 of a lead bryostatin analog, a position known to be crucial for binding to and modulation of protein kinase C (PKC), did not abrogate the anti-CHIKV activity of the scaffold, putatively indicating the involvement of a pathway independent of PKC. The work detailed in this study demonstrates that salicylate-derived analog 1 and two capped analogs (2 and 3) are not merely cytoprotective compounds, but act as selective and specific inhibitors of CHIKV replication. Further, a detailed comparative analysis of the effect of the non-capped versus the two capped analogs revealed that compound 1 acts both at early and late stages in the chikungunya virus replication cycle, while the capped analogs only interfere with a later stage process. Co-dosing with the PKC inhibitors sotrastaurin and Gö6976 counteracts the antiviral activity of compound 1 without affecting that of capped analogs 2 and 3, providing further evidence that the latter elicit their anti-CHIKV activity independently of PKC. Remarkably, treatment of CHIKV-infected cells with a combination of compound 1 and a capped analog resulted in a pronounced synergistic antiviral effect. Thus, these salicylate-based bryostatin analogs can inhibit CHIKV replication through a novel, yet still elusive, non-PKC dependent pathway.
View details for DOI 10.1016/j.bcp.2016.09.020
View details for PubMedID 27664855
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Inhibition of Chikungunya Virus-Induced Cell Death by Salicylate-Derived Bryostatin Analogues Provides Additional Evidence for a PKC-Independent Pathway
JOURNAL OF NATURAL PRODUCTS
2016; 79 (4): 680-684
Abstract
Chikungunya virus (CHIKV) has been spreading rapidly, with over one million confirmed or suspected cases in the Americas since late 2013. Infection with CHIKV causes devastating arthritic and arthralgic symptoms. Currently, there is no therapy to treat this disease, and the only medications focus on relief of symptoms. Recently, protein kinase C (PKC) modulators have been reported to inhibit CHIKV-induced cell death in cell assays. The salicylate-derived bryostatin analogues described here are structurally simplified PKC modulators that are more synthetically accessible than the natural product bryostatin 1, a PKC modulator and clinical lead for the treatment of cancer, Alzheimer's disease, and HIV eradication. Evaluation of the anti-CHIKV activity of these salicylate-derived bryostatin analogues in cell culture indicates that they are among the most potent cell-protective agents reported to date. Given that they are more accessible and significantly more active than the parent natural product, they represent new therapeutic leads for controlling CHIKV infection. Significantly, these analogues also provide evidence for the involvement of a PKC-independent pathway. This adds a fundamentally distinct aspect to the importance or involvement of PKC modulation in inhibition of chikungunya virus replication, a topic of recent and growing interest.
View details for DOI 10.1021/acs.jnatprod.5b01017
View details for Web of Science ID 000374915800002
View details for PubMedID 26900711
View details for PubMedCentralID PMC4942189
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Simplified Bryostatin Analogues Protect Cells from Chikungunya Virus-Induced Cell Death
JOURNAL OF NATURAL PRODUCTS
2016; 79 (4): 675-679
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus showing a recent resurgence and rapid spread worldwide. While vaccines are under development, there are currently no therapies to treat this disease, except for over-the-counter (OTC) analgesics, which alleviate the devastating arthritic and arthralgic symptoms. To identify novel inhibitors of the virus, analogues of the natural product bryostatin 1, a clinical lead for the treatment of cancer, Alzheimer's disease, and HIV eradication, were investigated for in vitro antiviral activity and were found to be among the most potent inhibitors of CHIKV replication reported to date. Bryostatin-based therapeutic efforts and even recent anti-CHIKV strategies have centered on modulation of protein kinase C (PKC). Intriguingly, while the C ring of bryostatin primarily drives interactions with PKC, A- and B-ring functionality in these analogues has a significant effect on the observed cell-protective activity. Significantly, bryostatin 1 itself, a potent pan-PKC modulator, is inactive in these assays. These new findings indicate that the observed anti-CHIKV activity is not solely mediated by PKC modulation, suggesting possible as yet unidentified targets for CHIKV therapeutic intervention. The high potency and low toxicity of these bryologs make them promising new leads for the development of a CHIKV treatment.
View details for DOI 10.1021/acs.jnatprod.5b01016
View details for Web of Science ID 000374915800001
View details for PubMedID 26900625
View details for PubMedCentralID PMC4928627
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Cell-Penetrating, Guanidinium-Rich Oligophosphoesters: Effective and Versatile Molecular Transporters for Drug and Probe Delivery.
Journal of the American Chemical Society
2016; 138 (10): 3510-3517
Abstract
The design, synthesis, and biological evaluation of a new family of highly effective cell-penetrating molecular transporters, guanidinium-rich oligophosphoesters, are described. These unique transporters are synthesized in two steps, irrespective of oligomer length, by the organocatalytic ring-opening polymerization (OROP) of 5-membered cyclic phospholane monomers followed by oligomer deprotection. Varying the initiating alcohol results in a wide variety of cargo attachment strategies for releasable or nonreleasable transporter applications. Initiation of oligomerization with a fluorescent probe produces, upon deprotection, a transporter-probe conjugate that is shown to readily enter multiple cell lines in a dose-dependent manner. These new transporters are superior in cell uptake to previously studied guanidinium-rich oligocarbonates and oligoarginines, showing over 2-fold higher uptake than the former and 6-fold higher uptake than the latter. Initiation with a protected thiol gives, upon deprotection, thiol-terminated transporters which can be thiol-click conjugated to a variety of probes, drugs and other cargos as exemplified by the conjugation and delivery of the model probe fluorescein-maleimide and the medicinal agent paclitaxel (PTX) into cells. Of particular significance given that drug resistance is a major cause of chemotherapy failure, the PTX-transporter conjugate, designed to evade Pgp export and release free PTX after cell entry, shows efficacy against PTX-resistant ovarian cancer cells. Collectively this study introduces a new and highly effective class of guanidinium-rich cell-penetrating transporters and methodology for their single-step conjugation to drugs and probes, and demonstrates that the resulting drug/probe-conjugates readily enter cells, outperforming previously reported guanidinium-rich oligocarbonates and peptide transporters.
View details for DOI 10.1021/jacs.5b13452
View details for PubMedID 26900771
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Cell-Penetrating, Guanidinium-Rich Oligophosphoesters: Effective and Versatile Molecular Transporters for Drug and Probe Delivery
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2016; 138 (10): 3510-3517
Abstract
The design, synthesis, and biological evaluation of a new family of highly effective cell-penetrating molecular transporters, guanidinium-rich oligophosphoesters, are described. These unique transporters are synthesized in two steps, irrespective of oligomer length, by the organocatalytic ring-opening polymerization (OROP) of 5-membered cyclic phospholane monomers followed by oligomer deprotection. Varying the initiating alcohol results in a wide variety of cargo attachment strategies for releasable or nonreleasable transporter applications. Initiation of oligomerization with a fluorescent probe produces, upon deprotection, a transporter-probe conjugate that is shown to readily enter multiple cell lines in a dose-dependent manner. These new transporters are superior in cell uptake to previously studied guanidinium-rich oligocarbonates and oligoarginines, showing over 2-fold higher uptake than the former and 6-fold higher uptake than the latter. Initiation with a protected thiol gives, upon deprotection, thiol-terminated transporters which can be thiol-click conjugated to a variety of probes, drugs and other cargos as exemplified by the conjugation and delivery of the model probe fluorescein-maleimide and the medicinal agent paclitaxel (PTX) into cells. Of particular significance given that drug resistance is a major cause of chemotherapy failure, the PTX-transporter conjugate, designed to evade Pgp export and release free PTX after cell entry, shows efficacy against PTX-resistant ovarian cancer cells. Collectively this study introduces a new and highly effective class of guanidinium-rich cell-penetrating transporters and methodology for their single-step conjugation to drugs and probes, and demonstrates that the resulting drug/probe-conjugates readily enter cells, outperforming previously reported guanidinium-rich oligocarbonates and peptide transporters.
View details for DOI 10.1021/jacs.5b13452
View details for Web of Science ID 000372477700036
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Bioorthogonal Catalysis: A General Method To Evaluate Metal Catalyzed Reactions in Real Time in Living Systems Using a Cellular Luciferase Reporter System
BIOCONJUGATE CHEMISTRY
2016; 27 (2): 376-382
Abstract
The development of abiological catalysts that can function in biological systems is an emerging subject of importance with significant ramifications in synthetic chemistry and the life sciences. Herein we report a biocompatible ruthenium complex [Cp(MQA)Ru(C3H5)](+)PF6(-) 2 (Cp = cyclopentadienyl, MQA = 4-methoxyquinoline-2-carboxylate) and a general analytical method for evaluating its performance in real time based on a luciferase reporter system amenable to high throughput screening in cells and by extension to evaluation in luciferase transgenic animals. Precatalyst 2 activates alloc-protected aminoluciferin 4b, a bioluminescence pro-probe, and releases the active luminophore, aminoluciferin (4a), in the presence of luciferase-transfected cells. The formation and enzymatic turnover of 4a, an overall process selected because it emulates pro-drug activation and drug turnover by an intracellular target, is evaluated in real time by photon counting as 4a is converted by intracellular luciferase to oxyaminoluciferin and light. Interestingly, while the catalytic conversion (activation) of 4b to 4a in water produces multiple products, the presence of biological nucleophiles such as thiols prevents byproduct formation and provides almost exclusively luminophore 4a. Our studies show that precatalyst 2 activates 4b extracellularly, exhibits low toxicity at concentrations relevant to catalysis, and is comparably effective in two different cell lines. This proof of concept study shows that precatalyst 2 is a promising lead for bioorthogonal catalytic activation of pro-probes and, by analogy, similarly activatable pro-drugs. More generally, this study provides an analytical method to measure abiological catalytic activation of pro-probes and, by analogy with our earlier studies on pro-Taxol, similarly activatable pro-drugs in real time using a coupled biological catalyst that mediates a bioluminescent readout, providing tools for the study of imaging signal amplification and of targeted therapy.
View details for DOI 10.1021/acs.bioconjchem.5b00469
View details for Web of Science ID 000370582600012
View details for PubMedID 26367192
View details for PubMedCentralID PMC4772775
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Cellular delivery and photochemical release of a caged inositol-pyrophosphate induces PH-domain translocation in cellulo.
Nature communications
2016; 7: 10622-?
Abstract
Inositol pyrophosphates, such as diphospho-myo-inositol pentakisphosphates (InsP7), are an important family of signalling molecules, implicated in many cellular processes and therapeutic indications including insulin secretion, glucose homeostasis and weight gain. To understand their cellular functions, chemical tools such as photocaged analogues for their real-time modulation in cells are required. Here we describe a concise, modular synthesis of InsP7 and caged InsP7. The caged molecule is stable and releases InsP7 only on irradiation. While photocaged InsP7 does not enter cells, its cellular uptake is achieved using nanoparticles formed by association with a guanidinium-rich molecular transporter. This novel synthesis and unprecedented polyphosphate delivery strategy enable the first studies required to understand InsP7 signalling in cells with controlled spatiotemporal resolution. It is shown herein that cytoplasmic photouncaging of InsP7 leads to translocation of the PH-domain of Akt, an important signalling-node kinase involved in glucose homeostasis, from the membrane into the cytoplasm.
View details for DOI 10.1038/ncomms10622
View details for PubMedID 26842801
View details for PubMedCentralID PMC4743007
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Award Address (Arthur C. Cope Award sponsored by the Arthur C. Cope Fund). Chemistry-medicine continuum: Computer-guided, synthesis-informed design of new therapeutic leads for HIV/AIDS eradication, Alzheimer's disease, and cancer
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000432475702339
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Design, synthesis, and evaluation of novel guanidinium-rich, glycerol-derived oligocarbonates for the complexation, delivery, and release of siRNA
AMER CHEMICAL SOC. 2015
View details for Web of Science ID 000432475702416
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Tetramethyleneethane Equivalents: Recursive Reagents for Serialized Cycloadditions
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2015; 137 (28): 9088-9093
Abstract
New reactions and reagents that allow for multiple bond-forming events per synthetic operation are required to achieve structural complexity and thus value with step-, time-, cost-, and waste-economy. Here we report a new class of reagents that function like tetramethyleneethane (TME), allowing for back-to-back [4 + 2] cycloadditions, thereby amplifying the complexity-increasing benefits of Diels-Alder and metal-catalyzed cycloadditions. The parent recursive reagent, 2,3-dimethylene-4-trimethylsilylbutan-1-ol (DMTB), is readily available from the metathesis of ethylene and THP-protected 4-trimethylsilylbutyn-1-ol. DMTB and related reagents engage diverse dienophiles in an initial Diels-Alder or metal-catalyzed [4 + 2] cycloaddition, triggering a subsequent vinylogous Peterson elimination that recursively generates a new diene for a second cycloaddition. Overall, this multicomponent catalytic cascade produces in one operation carbo- and heterobicyclic building blocks for the synthesis of a variety of natural products, therapeutic leads, imaging agents, and materials. Its application to the three step synthesis of a new solvatochromic fluorophore, N-ethyl(6-N,N-dimethylaminoanthracene-2,3-dicarboximide) (6-DMA), and the photophysical characterization of this fluorophore are described.
View details for DOI 10.1021/jacs.5b04091
View details for Web of Science ID 000358556200035
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Tetramethyleneethane Equivalents: Recursive Reagents for Serialized Cycloadditions.
Journal of the American Chemical Society
2015; 137 (28): 9088-93
Abstract
New reactions and reagents that allow for multiple bond-forming events per synthetic operation are required to achieve structural complexity and thus value with step-, time-, cost-, and waste-economy. Here we report a new class of reagents that function like tetramethyleneethane (TME), allowing for back-to-back [4 + 2] cycloadditions, thereby amplifying the complexity-increasing benefits of Diels-Alder and metal-catalyzed cycloadditions. The parent recursive reagent, 2,3-dimethylene-4-trimethylsilylbutan-1-ol (DMTB), is readily available from the metathesis of ethylene and THP-protected 4-trimethylsilylbutyn-1-ol. DMTB and related reagents engage diverse dienophiles in an initial Diels-Alder or metal-catalyzed [4 + 2] cycloaddition, triggering a subsequent vinylogous Peterson elimination that recursively generates a new diene for a second cycloaddition. Overall, this multicomponent catalytic cascade produces in one operation carbo- and heterobicyclic building blocks for the synthesis of a variety of natural products, therapeutic leads, imaging agents, and materials. Its application to the three step synthesis of a new solvatochromic fluorophore, N-ethyl(6-N,N-dimethylaminoanthracene-2,3-dicarboximide) (6-DMA), and the photophysical characterization of this fluorophore are described.
View details for DOI 10.1021/jacs.5b04091
View details for PubMedID 25961416
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Studies on the regio- and diastereo-selective epoxidation of daphnanes and tiglianes
TETRAHEDRON LETTERS
2015; 56 (23): 3423-3427
Abstract
Daphnanes and tiglianes are diterpenes with a shared tricyclic 5-7-6 ring system. Many members exhibit significant biological activities often associated with protein kinase C signaling. Many of these natural products (~100) have a C6-C7 α-epoxide whose influence on biological activity is little studied. Using the more readily available phorbol ester PDBu as a test substrate, we report an efficient, and potentially general, α-epoxidation method based on a vanadium-catalyzed asymmetric epoxidation with bishydroxamic acid (BHA) ligands.
View details for DOI 10.1016/j.tetlet.2015.01.126
View details for Web of Science ID 000356544800113
View details for PubMedCentralID PMC4449265
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Studies on the regio- and diastereo-selective epoxidation of daphnanes and tiglianes.
Tetrahedron letters
2015; 56 (23): 3423-3427
Abstract
Daphnanes and tiglianes are diterpenes with a shared tricyclic 5-7-6 ring system. Many members exhibit significant biological activities often associated with protein kinase C signaling. Many of these natural products (~100) have a C6-C7 α-epoxide whose influence on biological activity is little studied. Using the more readily available phorbol ester PDBu as a test substrate, we report an efficient, and potentially general, α-epoxidation method based on a vanadium-catalyzed asymmetric epoxidation with bishydroxamic acid (BHA) ligands.
View details for DOI 10.1016/j.tetlet.2015.01.126
View details for PubMedID 26034334
View details for PubMedCentralID PMC4449265
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Toward a Biorelevant Structure of Protein Kinase C Bound Modulators: Design, Synthesis, and Evaluation of Labeled Bryostatin Analogues for Analysis with Rotational Echo Double Resonance NMR Spectroscopy
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2015; 137 (10): 3678-3685
Abstract
Protein kinase C (PKC) modulators are currently of great importance in preclinical and clinical studies directed at cancer, immunotherapy, HIV eradication, and Alzheimer's disease. However, the bound conformation of PKC modulators in a membrane environment is not known. Rotational echo double resonance (REDOR) NMR spectroscopy could uniquely address this challenge. However, REDOR NMR requires strategically labeled, high affinity ligands to determine interlabel distances from which the conformation of the bound ligand in the PKC-ligand complex could be identified. Here we report the first computer-guided design and syntheses of three bryostatin analogues strategically labeled for REDOR NMR analysis. Extensive computer analyses of energetically accessible analogue conformations suggested preferred labeling sites for the identification of the PKC-bound conformers. Significantly, three labeled analogues were synthesized, and, as required for REDOR analysis, all proved highly potent with PKC affinities (∼1 nM) on par with bryostatin. These potent and strategically labeled bryostatin analogues are new structural leads and provide the necessary starting point for projected efforts to determine the PKC-bound conformation of such analogues in a membrane environment, as needed to design new PKC modulators and understand PKC-ligand-membrane structure and dynamics.
View details for DOI 10.1021/jacs.5600886
View details for Web of Science ID 000351420800039
View details for PubMedID 25710634
View details for PubMedCentralID PMC4405261
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Catalytic Efficiency Is a Function of How Rhodium(I) (5 + 2) Catalysts Accommodate a Conserved Substrate Transition State Geometry: Induced Fit Model for Explaining Transition Metal Catalysis.
ACS catalysis
2015; 5 (3): 1758-1763
Abstract
The origins of differential catalytic reactivities of four Rh(I) catalysts and their derivatives in the (5 + 2) cycloaddition reaction were elucidated using density functional theory. Computed free energy spans are in excellent agreement with known experimental rates. For every catalyst, the substrate geometries in the transition state remained constant (<0.1 Å RMSD for atoms involved in bond-making and -breaking processes). Catalytic efficiency is shown to be a function of how well the catalyst accommodates the substrate transition state geometry and electronics. This shows that the induced fit model for explaining biological catalysis may be relevant to transition metal catalysis. This could serve as a general model for understanding the origins of efficiencies of catalytic reactions.
View details for DOI 10.1021/cs501828e
View details for PubMedID 26146588
View details for PubMedCentralID PMC4487883
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Guanidinium-Rich, Glycerol-Derived Oligocarbonates: A New Class of Cell-Penetrating Molecular Transporters That Complex, Deliver, and Release siRNA.
Molecular pharmaceutics
2015; 12 (3): 742-750
Abstract
A highly versatile and step-economical route to a new class of guanidinium-rich molecular transporters and evaluation of their ability to complex, deliver, and release siRNA are described. These new drug/probe delivery systems are prepared in only two steps, irrespective of length or composition, using an organocatalytic ring-opening co-oligomerization of glycerol-derived cyclic carbonate monomers incorporating either protected guanidine or lipid side chains. The resultant amphipathic co-oligomers are highly effective vehicles for siRNA delivery, providing an excellent level of target protein suppression (>85%). These new oligocarbonates are nontoxic at levels required for cell penetration and can be tuned for particle size. Relative to the previously reported methyl(trimethylene)carbonate (MTC) scaffold, the ether linkage at C2 in the new transporters markedly enhances the stability of the siRNA/co-oligomer complexes. Both hybrid co-oligomers, containing a mixture of glycerol- and MTC-derived monomers, and co-oligomers containing only glycerol monomers are found to provide tunable control over siRNA complex stability. On the basis of a glycerol and CO2 backbone, these new co-oligomers represent a rapidly tunable and biocompatible siRNA delivery system that is highly effective in suppressing target protein synthesis.
View details for DOI 10.1021/mp500581r
View details for PubMedID 25588140
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Function through Synthesis-Informed Design
ACCOUNTS OF CHEMICAL RESEARCH
2015; 48 (3): 752-760
Abstract
In 1996, a snapshot of the field of synthesis was provided by many of its thought leaders in a Chemical Reviews thematic issue on "Frontiers in Organic Synthesis". This Accounts of Chemical Research thematic issue on "Synthesis, Design, and Molecular Function" is intended to provide further perspective now from well into the 21st century. Much has happened in the past few decades. The targets, methods, strategies, reagents, procedures, goals, funding, practices, and practitioners of synthesis have changed, some in dramatic ways as documented in impressive contributions to this issue. However, a constant for most synthesis studies continues to be the goal of achieving function with synthetic economy. Whether in the form of new catalysts, reagents, therapeutic leads, diagnostics, drug delivery systems, imaging agents, sensors, materials, energy generation and storage systems, bioremediation strategies, or molecules that challenge old theories or test new ones, the function of a target has been and continues to be a major and compelling justification for its synthesis. While the targets of synthesis have historically been heavily represented by natural products, increasingly design, often inspired by natural structures, is providing a new source of target structures exhibiting new or natural functions and new or natural synthetic challenges. Complementing isolation and screening approaches to new target identification, design enables one to create targets de novo with an emphasis on sought-after function and synthetic innovation with step-economy. Design provides choice. It allows one to determine how close a synthesis will come to the ideal synthesis and how close a structure will come to the ideal function. In this Account, we address studies in our laboratory on function-oriented synthesis (FOS), a strategy to achieve function by design and with synthetic economy. By starting with function rather than structure, FOS places an initial emphasis on target design, thereby harnessing the power of chemists and computers to create new structures with desired functions that could be prepared in a simple, safe, economical, and green, if not ideal, fashion. Reported herein are examples of FOS associated with (a) molecular recognition, leading to the first designed phorbol-inspired protein kinase C regulatory ligands, the first designed bryostatin analogs, the newest bryologs, and a new family of designed kinase inhibitors, (b) target modification, leading to highly simplified but functionally competent photonucleases-molecules that cleave DNA upon photoactivation, (c) drug delivery, leading to cell penetrating molecular transporters, molecules that ferry other attached or complexed molecules across biological barriers, and (d) new reactivity-regenerating reagents in the form of functional equivalents of butatrienes, reagents that allow for back-to-back three-component cycloaddition reactions, thus achieving structural complexity and value with step-economy. While retrosynthetic analysis seeks to identify the best way to make a target, retrofunction analysis seeks to identify the best targets to make. In essence, form (structure) follows function.
View details for DOI 10.1021/acs.accounts.5b00004
View details for Web of Science ID 000351326900027
View details for PubMedID 25742599
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Catalytic Efficiency Is a Function of How Rhodium(I) (5+2) Catalysts Accommodate a Conserved Substrate Transition State Geometry: Induced Fit Model for Explaining Transition Metal Catalysis
ACS CATALYSIS
2015; 5 (3): 1758-1763
Abstract
The origins of differential catalytic reactivities of four Rh(I) catalysts and their derivatives in the (5 + 2) cycloaddition reaction were elucidated using density functional theory. Computed free energy spans are in excellent agreement with known experimental rates. For every catalyst, the substrate geometries in the transition state remained constant (<0.1 Å RMSD for atoms involved in bond-making and -breaking processes). Catalytic efficiency is shown to be a function of how well the catalyst accommodates the substrate transition state geometry and electronics. This shows that the induced fit model for explaining biological catalysis may be relevant to transition metal catalysis. This could serve as a general model for understanding the origins of efficiencies of catalytic reactions.
View details for DOI 10.1021/cs501828e
View details for Web of Science ID 000350843500044
View details for PubMedCentralID PMC4487883
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Art, architecture, and the molecular frontier.
Accounts of chemical research
2015; 48 (8): 2169–70
View details for PubMedID 26282016
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Function through bio-inspired, synthesis-informed design: step-economical syntheses of designed kinase inhibitors†Dedicated to Max Malacria, a friend and scholar whose science and creative contributions to step-economical synthesis have inspired us all and moved the field closer to the ideal.‡Electronic supplementary information (ESI) available: Synthetic procedures and spectral data. See DOI: 10.1039/c4qo00228hClick here for additional data file.
Organic chemistry frontiers : an international journal of organic chemistry
2014; 1 (10): 1166-1171
Abstract
The human kinome comprises over 500 protein kinases. When mutated or over-expressed, many play critical roles in abnormal cellular functions associated with cancer, cardiovascular disease and neurological disorders. Here we report a step-economical approach to designed kinase inhibitors inspired by the potent, but non-selective, natural product staurosporine, and synthetically enabled by a novel, complexity-increasing, serialized [5 + 2]/[4 + 2] cycloaddition strategy. This function-oriented synthesis approach rapidly affords tunable scaffolds, and produced a low nanomolar inhibitor of protein kinase C.
View details for PubMedID 25632347
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Reactivity and Chemoselectivity of Allenes in Rh(I)-Catalyzed Intermolecular (5+2) Cycloadditions with Vinylcyclopropanes: Allene-Mediated Rhodacycle Formation Can Poison Rh(I)-Catalyzed Cycloadditions
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2014; 136 (49): 17273-17283
Abstract
Allenes are important 2π building blocks in organic synthesis and engage as 2-carbon components in many metal-catalyzed reactions. Wender and co-workers discovered that methyl substituents on the terminal allene double bond counterintuitively change the reactivities of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with vinylcyclopropanes (VCPs). More sterically encumbered allenes afford higher cycloadduct yields, and such effects are also observed in other Rh(I)-catalyzed intermolecular cycloadditions. Through density functional theory calculations (B3LYP and M06) and experiment, we explored this enigmatic reactivity and selectivity of allenes in [Rh(CO)2Cl]2-catalyzed intermolecular (5 + 2) cycloadditions with VCPs. The apparent low reactivity of terminally unsubstituted allenes is associated with a competing allene dimerization that irreversibly sequesters rhodium. With terminally substituted allenes, steric repulsion between the terminal substituents significantly increases the barrier of allene dimerization while the barrier of the (5 + 2) cycloaddition is not affected, and thus the cycloaddition prevails. Computation has also revealed the origin of chemoselectivity in (5 + 2) cycloadditions with allene-ynes. Although simple allene and acetylene have similar reaction barriers, intermolecular (5 + 2) cycloadditions of allene-ynes occur exclusively at the terminal allene double bond. The terminal double bond is more reactive due to the enhanced d-π* backdonation. At the same time, insertion of the internal double bond of an allene-yne has a higher barrier as it would break π conjugation. Substituted alkynes are more difficult to insert compared with acetylene, because of the steric repulsion from the additional substituents. This leads to the greater reactivity of the allene double bond relative to the alkynyl group in allene-ynes.
View details for DOI 10.1021/ja5098308
View details for Web of Science ID 000346544200044
View details for PubMedID 25379606
View details for PubMedCentralID PMC4277756
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Computer-Guided Design, Synthesis, and Protein Kinase C Affinity of a New. Salicylate-Based Class of Bryostatin Analogs
ORGANIC LETTERS
2014; 16 (19): 5136-5139
Abstract
Bryostatin 1 is in clinical trials for the treatment of cancer and Alzheimer's disease and is a candidate for a first-in-class approach to HIV/AIDS eradication. It is neither readily available nor optimally suited for clinical use. Using a function oriented synthesis strategy, a new class of bryostatin-inspired analogs was designed with a simplified salicylate-derived subunit, enabling step-economical synthesis (23 total steps) of agents exhibiting bryostatin-like affinity to protein kinase C (PKC).
View details for DOI 10.1021/ol502491f
View details for Web of Science ID 000342719500043
View details for PubMedCentralID PMC4334246
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Computer-guided design, synthesis, and protein kinase C affinity of a new salicylate-based class of bryostatin analogs.
Organic letters
2014; 16 (19): 5136-5139
Abstract
Bryostatin 1 is in clinical trials for the treatment of cancer and Alzheimer's disease and is a candidate for a first-in-class approach to HIV/AIDS eradication. It is neither readily available nor optimally suited for clinical use. Using a function oriented synthesis strategy, a new class of bryostatin-inspired analogs was designed with a simplified salicylate-derived subunit, enabling step-economical synthesis (23 total steps) of agents exhibiting bryostatin-like affinity to protein kinase C (PKC).
View details for DOI 10.1021/ol502491f
View details for PubMedID 25238583
View details for PubMedCentralID PMC4334246
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Improved protein kinase C affinity through final step diversification of a simplified salicylate-derived bryostatin analog scaffold.
Organic letters
2014; 16 (19): 5140-5143
Abstract
Bryostatin 1, in clinical trials or preclinical development for cancer, Alzheimer's disease, and a first-of-its-kind strategy for HIV/AIDS eradication, is neither readily available nor optimally suited for clinical use. In preceding work, we disclosed a new class of simplified bryostatin analogs designed for ease of access and tunable activity. Here we describe a final step diversification strategy that provides, in only 25 synthetic steps, simplified and tunable analogs with bryostatin-like PKC modulatory activities.
View details for DOI 10.1021/ol502492b
View details for PubMedID 25238640
View details for PubMedCentralID PMC4334251
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Improved Protein Kinase C Affinity through Final Step Diversification of a Simplified Salicylate-Derived Bryostatin Analog Scaffold
ORGANIC LETTERS
2014; 16 (19): 5140-5143
Abstract
Bryostatin 1, in clinical trials or preclinical development for cancer, Alzheimer's disease, and a first-of-its-kind strategy for HIV/AIDS eradication, is neither readily available nor optimally suited for clinical use. In preceding work, we disclosed a new class of simplified bryostatin analogs designed for ease of access and tunable activity. Here we describe a final step diversification strategy that provides, in only 25 synthetic steps, simplified and tunable analogs with bryostatin-like PKC modulatory activities.
View details for DOI 10.1021/ol502492b
View details for Web of Science ID 000342719500044
View details for PubMedCentralID PMC4334251
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Toward HIV eradication strategies: Designed, synthetically accessible bryostatin and prostratin analogs potently induce activation of latent HIV reservoirs in vitro and ex vivo
AMER CHEMICAL SOC. 2014
View details for Web of Science ID 000349167406327
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Cell-penetrating, guanidinium-rich molecular transporters for overcoming efflux-mediated multidrug resistance.
Molecular pharmaceutics
2014; 11 (8): 2553-2565
Abstract
Multidrug resistance (MDR) is a major cause of chemotherapy failure in the clinic. Drugs that were once effective against naïve disease subsequently prove ineffective against recurrent disease, which often exhibits an MDR phenotype. MDR can be attributed to many factors; often dominating among these is the ability of a cell to suppress or block drug entry through upregulation of membrane-bound drug efflux pumps. Efflux pumps exhibit polyspecificity, recognizing and exporting many different types of drugs, especially those whose lipophilic nature contributes to residence in the membrane. We have developed a general strategy to overcome efflux-based resistance. This strategy involves conjugating a known drug that succumbs to efflux-mediated resistance to a cell-penetrating molecular transporter, specifically, the cell-penetrating peptide (CPP), d-octaarginine. The resultant conjugates are discrete single entities (not particle mixtures) and highly water-soluble. They rapidly enter cells, are not substrates for efflux pumps, and release the free drug only after cellular entry at a rate controlled by linker design and favored by target cell chemistry. This general strategy can be applied to many classes of drugs and allows for an exceptionally rapid advance to clinical testing, especially of drugs that succumb to resistance. The efficacy of this strategy has been successfully demonstrated with Taxol in cellular and animal models of resistant cancer and with ex vivo samples from patients with ovarian cancer. Next generation efforts in this area will involve the extension of this strategy to other chemotherapeutics and other MDR-susceptible diseases.
View details for DOI 10.1021/mp500161z
View details for PubMedID 24798708
View details for PubMedCentralID PMC4123947
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Bioengineered Vaults: Self-Assembling Protein Shell-Lipophilic Core Nanoparticles for Drug Delivery
ACS NANO
2014; 8 (8): 7723-7732
Abstract
We report a novel approach to a new class of bioengineered, monodispersed, self-assembling vault nanoparticles consisting of a protein shell exterior with a lipophilic core interior designed for drug and probe delivery. Recombinant vaults were engineered to contain a small amphipathic α-helix derived from the nonstructural protein 5A of hepatitis C virus, thereby creating within the vault lumen a lipophilic microenvironment into which lipophilic compounds could be reversibly encapsulated. Multiple types of electron microscopy showed that attachment of this peptide resulted in larger than expected additional mass internalized within the vault lumen attributable to incorporation of host lipid membrane constituents spanning the vault waist (>35 nm). These bioengineered lipophilic vaults reversibly associate with a sample set of therapeutic compounds, including all-trans retinoic acid, amphotericin B, and bryostatin 1, incorporating hundreds to thousands of drug molecules per vault nanoparticle. Bryostatin 1 is of particular therapeutic interest because of its ability to potently induce expression of latent HIV, thus representing a preclinical lead in efforts to eradicate HIV/AIDS. Vaults loaded with bryostatin 1 released free drug, resulting in activation of HIV from provirus latency in vitro and induction of CD69 biomarker expression following intravenous injection into mice. The ability to preferentially and reversibly encapsulate lipophilic compounds into these novel bioengineered vault nanoparticles greatly advances their potential use as drug delivery systems.
View details for DOI 10.1021/nn5002694
View details for Web of Science ID 000340992300017
View details for PubMedID 25061969
View details for PubMedCentralID PMC4148163
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Propargyltrimethylsilanes as allene equivalents in transition metal-catalyzed [5 + 2] cycloadditions.
Organic letters
2014; 16 (11): 2923-2925
Abstract
Conventional allenes have not been effective π-reactive 2-carbon components in many intermolecular cycloadditions including metal-catalyzed [5 + 2] cycloadditions. We report herein that rhodium-catalyzed [5 + 2] cycloadditions of propargyltrimethylsilanes and vinylcyclopropanes provide, after in situ protodesilylation, a highly efficient route to formal allene cycloadducts. Propargyltrimethylsilanes function as safe, easily handled synthetic equivalents of gaseous allenes and hard-to-access monosubstituted allenes. In this one-flask procedure, they provide cycloadducts of what is formally addition to the more sterically encumbered allene double bond.
View details for DOI 10.1021/ol501114q
View details for PubMedID 24819093
View details for PubMedCentralID PMC4051429
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Structural complexity through multicomponent cycloaddition cascades enabled by dual-purpose, reactivity regenerating 1,2,3-triene equivalents
NATURE CHEMISTRY
2014; 6 (5): 448-452
Abstract
Multicomponent reactions allow for more bond-forming events per synthetic operation, enabling more step- and time-economical conversion of simple starting materials to complex and thus value-added targets. These processes invariably require that reactivity be relayed from intermediate to intermediate over several mechanistic steps until a termination event produces the final product. Here, we report a multicomponent process in which a novel 1,2,3-butatriene equivalent (TMSBO: TMSCH2C≡CCH2OH) engages chemospecifically as a two-carbon alkyne component in a metal-catalysed [5 + 2] cycloaddition with a vinylcyclopropane to produce an intermediate cycloadduct. Under the reaction conditions, this intermediate undergoes a remarkably rapid 1,4-Peterson elimination, producing a reactive four-carbon diene intermediate that is readily intercepted in either a metal-catalysed or thermal [4 + 2] cycloaddition. TMSBO thus serves as an yne-to-diene transmissive reagent coupling two powerful and convergent cycloadditions--the homologous Diels-Alder and Diels-Alder cycloadditions--through a vinylogous Peterson elimination, and enabling flexible access to diverse polycycles.
View details for DOI 10.1038/NCHEM.1917
View details for Web of Science ID 000334919700017
View details for PubMedID 24755598
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Toward the ideal synthesis and molecular function through synthesis-informed design
NATURAL PRODUCT REPORTS
2014; 31 (4): 433-440
Abstract
This Highlight describes factors that contribute to an ideal synthesis, including economies (step, time, atom, solvent, energy) and orientations (target, diversity, safety, function), and the role of synthesis-informed design directed at function in advancing synthesis and its impact on science.
View details for DOI 10.1039/c4np00013g
View details for Web of Science ID 000333040900004
View details for PubMedID 24589860
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Rethinking the Role of Natural Products: Function-Oriented Synthesis, Bryostatin, and Bryologs
NATURAL PRODUCTS IN MEDICINAL CHEMISTRY
2014; 60: 475-543
View details for Web of Science ID 000354997600016
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Function through bio-inspired, synthesis-informed design: step-economical syntheses of designed kinase inhibitors
ORGANIC CHEMISTRY FRONTIERS
2014; 1 (10): 1166-1171
Abstract
The human kinome comprises over 500 protein kinases. When mutated or over-expressed, many play critical roles in abnormal cellular functions associated with cancer, cardiovascular disease and neurological disorders. Here we report a step-economical approach to designed kinase inhibitors inspired by the potent, but non-selective, natural product staurosporine, and synthetically enabled by a novel, complexity-increasing, serialized [5 + 2]/[4 + 2] cycloaddition strategy. This function-oriented synthesis approach rapidly affords tunable scaffolds, and produced a low nanomolar inhibitor of protein kinase C.
View details for DOI 10.1039/c4qo00228h
View details for Web of Science ID 000364430800005
View details for PubMedCentralID PMC4304288
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Fifteen Years of Cell-Penetrating Guanidinium-Rich Molecular Transporters: Basic Science, Research Tools, and Clinical Applications
ACCOUNTS OF CHEMICAL RESEARCH
2013; 46 (12): 2944-2954
Abstract
All living systems require biochemical barriers. As a consequence, all drugs, imaging agents, and probes have targets that are either on, in, or inside of these barriers. Fifteen years ago, we initiated research directed at more fully understanding these barriers and at developing tools and strategies for breaching them that could be of use in basic research, imaging, diagnostics, and medicine. At the outset of this research and now to a lesser extent, the "rules" for drug design biased the selection of drug candidates mainly to those with an intermediate and narrow log P. At the same time, it was becoming increasingly apparent that Nature had long ago developed clever strategies to circumvent these "rules." In 1988, for example, independent reports documented the otherwise uncommon passage of a protein (HIV-Tat) across a membrane. A subsequent study implicated a highly basic domain in this protein (Tat49-57) in its cellular entry. This conspicuously contradictory behavior of a polar, highly charged peptide passing through a nonpolar membrane set the stage for learning how Nature had gotten around the current "rules" of transport. As elaborated in our studies and discussed in this Account, the key strategy used in Nature rests in part on the ability of a molecule to change its properties as a function of microenvironment; such molecules need to be polarity chameleons, polar in a polar milieu and relatively nonpolar in a nonpolar environment. Because this research originated in part with the protein Tat and its basic peptide domain, Tat49-57, the field focused heavily on peptides, even limiting its nomenclature to names such as "cell-penetrating peptides," "cell-permeating peptides," "protein transduction domains," and "membrane translocating peptides." Starting in 1997, through a systematic reverse engineering approach, we established that the ability of Tat49-57 to enter cells is not a function of its peptide backbone, but rather a function of the number and spatial array of its guanidinium groups. These function-oriented studies enabled us and others to design more effective peptidic agents and to think beyond the confines of peptidic systems to new and even more effective nonpeptidic agents. Because the function of passage across a cell membrane is not limited to or even best achieved with the peptide backbone, we referred to these agents by their shared function, "cell-penetrating molecular transporters." The scope of this molecular approach to breaching biochemical barriers has expanded remarkably in the past 15 years: enabling or enhancing the delivery of a wide range of cargos into cells and across other biochemical barriers, creating new tools for research, imaging, and diagnostics, and introducing new therapies into clinical trials.
View details for DOI 10.1021/ar4000554
View details for Web of Science ID 000328797300021
View details for PubMedID 23697862
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Toward the ideal synthesis and transformative therapies: the roles of step economy and function oriented synthesis
TETRAHEDRON
2013; 69 (36): 7529-7550
View details for DOI 10.1016/j.tet.2013.06.004
View details for Web of Science ID 000322939900002
View details for PubMedCentralID PMC3743450
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Toward the ideal synthesis and function through synthesis informed design: Approaches to AIDS eradication, treating Alzheimer's disease, and overcoming resistant cancer
AMER CHEMICAL SOC. 2013
View details for Web of Science ID 000329618405373
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Multiscale modeling of drug delivery nanosystems: Liposomes and cross linked nanospheres
AMER CHEMICAL SOC. 2013
View details for Web of Science ID 000329618404843
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Highly potent, synthetically accessible prostratin analogs induce latent HIV expression in vitro and ex vivo
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2013; 110 (29): 11698-11703
Abstract
Highly active antiretroviral therapy (HAART) decreases plasma viremia below the limits of detection in the majority of HIV-infected individuals, thus serving to slow disease progression. However, HAART targets only actively replicating virus and is unable to eliminate latently infected, resting CD4(+) T cells. Such infected cells are potentially capable of reinitiating virus replication upon cessation of HAART, thus leading to viral rebound. Agents that would eliminate these reservoirs, when used in combination with HAART, could thus provide a strategy for the eradication of HIV. Prostratin is a preclinical candidate that induces HIV expression from latently infected CD4(+) T cells, potentially leading to their elimination through a virus-induced cytopathic effect or host anti-HIV immunity. Here, we report the synthesis of a series of designed prostratin analogs and report in vitro and ex vivo studies of their activity relevant to induction of HIV expression. Members of this series are up to 100-fold more potent than the preclinical lead (prostratin) in binding to cell-free PKC, and in inducing HIV expression in a latently infected cell line and prostratin-like modulation of cell surface receptor expression in primary cells from HIV-negative donors. Significantly, selected members were also tested for HIV induction in resting CD4(+) T cells isolated from infected individuals receiving HAART and were found to exhibit potent induction activity. These more potent agents and by extension related tunable analogs now accessible through the studies described herein should facilitate research and preclinical advancement of this strategy for HIV/AIDS eradication.
View details for DOI 10.1073/pnas.1302634110
View details for Web of Science ID 000322086100023
View details for PubMedID 23812750
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Lead Diversification through a Prins-Driven Macrocyclization Strategy: Application to C13-Diversified Bryostatin Analogues
SYNTHESIS-STUTTGART
2013; 45 (13): 1815-1824
Abstract
The design, synthesis, and biological evaluation of a novel class of C13-diversified bryostatin analogues are described. An innovative and general strategy based on a Prins macrocyclization-nucleophilic trapping cascade was used to achieve late-stage diversification. In vitro analysis of selected library members revealed that modification at the C13 position of the bryostatin scaffold can be used as a diversification handle to regulate biological activity.
View details for DOI 10.1055/s-0033-1338860
View details for Web of Science ID 000321611500014
View details for PubMedCentralID PMC3963460
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Toward the Ideal Synthesis and Transformative Therapies: The Roles of Step Economy and Function Oriented Synthesis.
Tetrahedron
2013; 69 (36): 7529-7550
View details for DOI 10.1016/j.tet.2013.06.004
View details for PubMedID 23956471
View details for PubMedCentralID PMC3743450
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Mechanistic and Computational Studies of Exocyclic Stereocontrol in the Synthesis of Bryostatin-like Cis-2,6-Disubstituted 4-Alkylidenetetrahydropyrans by Prins Cyclization
JOURNAL OF ORGANIC CHEMISTRY
2013; 78 (1): 104-115
Abstract
The Prins cyclization of syn-β-hydroxy allylsilanes and aldehydes gives cis-2,6-disubstituted 4-alkylidenetetrahydropyrans as sole products in excellent yields regardless of the aldehyde (R″) or syn-β-hydroxy allylsilane substituent (R') used. By reversing the R″ and R' groups, complementary exocyclic stereocontrol can be achieved. When the anti-β-hydroxy allylsilanes are used, the Prins cyclization gives predominantly cis-2,6-disubstituted 4-alkylidenetetrahydropyrans, now with the opposite olefin geometry in excellent yield. The proposed reaction mechanism and the observed stereoselectivity for these processes are supported by DFT calculations.
View details for DOI 10.1021/jo301953h
View details for Web of Science ID 000313300000011
View details for PubMedID 23121542
View details for PubMedCentralID PMC3537866
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Lead Diversification through a Prins-Driven Macrocyclization Strategy: Application to C13-Diversified Bryostatin Analogues.
Synthesis
2013; 45 (13): 1815-1824
Abstract
The design, synthesis, and biological evaluation of a novel class of C13-diversified bryostatin analogues are described. An innovative and general strategy based on a Prins macrocyclization-nucleophilic trapping cascade was used to achieve late-stage diversification. In vitro analysis of selected library members revealed that modification at the C13 position of the bryostatin scaffold can be used as a diversification handle to regulate biological activity.
View details for DOI 10.1055/s-0033-1338860
View details for PubMedID 24672140
View details for PubMedCentralID PMC3963460
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Designed, synthetically accessible bryostatin analogues potently induce activation of latent HIV reservoirs in vitro
NATURE CHEMISTRY
2012; 4 (9): 705-710
Abstract
Bryostatin is a unique lead in the development of potentially transformative therapies for cancer, Alzheimer's disease and the eradication of HIV/AIDS. However, the clinical use of bryostatin has been hampered by its limited supply, difficulties in accessing clinically relevant derivatives, and side effects. Here, we address these problems through the step-economical syntheses of seven members of a new family of designed bryostatin analogues using a highly convergent Prins-macrocyclization strategy. We also demonstrate for the first time that such analogues effectively induce latent HIV activation in vitro with potencies similar to or better than bryostatin. Significantly, these analogues are up to 1,000-fold more potent in inducing latent HIV expression than prostratin, the current clinical candidate for latent virus induction. This study provides the first demonstration that designed, synthetically accessible bryostatin analogues could serve as superior candidates for the eradication of HIV/AIDS through induction of latent viral reservoirs in conjunction with current antiretroviral therapy.
View details for DOI 10.1038/NCHEM.1395
View details for Web of Science ID 000308214200007
View details for PubMedID 22914190
View details for PubMedCentralID PMC3428736
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Effect of Histone Deacetylase Inhibitors on HIV Production in Latently Infected, Resting CD4(+) T Cells From Infected Individuals Receiving Effective Antiretroviral Therapy
JOURNAL OF INFECTIOUS DISEASES
2012; 206 (5): 765-769
Abstract
Persistence of the latent viral reservoir has been recognized as a major obstacle to eradicating human immunodeficiency virus (HIV) in infected individuals receiving antiretroviral therapy. It has been suggested that histone deacetylase inhibitors (HDACis) may purge HIV in the latent viral reservoir. However, the effect of HDACis on the degree and extent of HIV expression in the latent viral reservoir has not been fully delineated. Here we demonstrate that HDACis do not induce HIV production in the latent viral reservoir of aviremic individuals. Therefore, alternative therapeutic strategies may be necessary to eliminate HIV in the latent viral reservoir.
View details for DOI 10.1093/infdis/jis412
View details for Web of Science ID 000307501800018
View details for PubMedID 22732922
View details for PubMedCentralID PMC3491743
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Designed guanidinium-rich amphipathic oligocarbonate molecular transporters complex, deliver and release siRNA in cells
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (33): 13171-13176
Abstract
The polyanionic nature of oligonucleotides and their enzymatic degradation present challenges for the use of siRNA in research and therapy; among the most notable of these is clinically relevant delivery into cells. To address this problem, we designed and synthesized the first members of a new class of guanidinium-rich amphipathic oligocarbonates that noncovalently complex, deliver, and release siRNA in cells, resulting in robust knockdown of target protein synthesis in vitro as determined using a dual-reporter system. The organocatalytic oligomerization used to synthesize these co-oligomers is step-economical and broadly tunable, affording an exceptionally quick strategy to explore chemical space for optimal siRNA delivery in varied applications. The speed and versatility of this approach and the biodegradability of the designed agents make this an attractive strategy for biological tool development, imaging, diagnostics, and therapeutic applications.
View details for DOI 10.1073/pnas.1211361109
View details for Web of Science ID 000307807000017
View details for PubMedID 22847412
View details for PubMedCentralID PMC3421195
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A molecular method for the delivery of small molecules and proteins across the cell wall of algae using molecular transporters
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2012; 109 (33): 13225-13230
Abstract
Interest in algae has significantly accelerated with the increasing recognition of their potentially unique role in medical, materials, energy, bioremediation, and synthetic biological research. However, the introduction of tools to study, control, or expand the inner-workings of algae has lagged behind. Here we describe a general molecular method based on guanidinium-rich molecular transporters (GR-MoTrs) for bringing small and large cargos into algal cells. Significantly, this method is shown to work in wild-type algae that have an intact cell wall. Developed using Chlamydomonas reinhardtii, this method is also successful with less studied algae including Neochloris oleoabundans and Scenedesmus dimorphus thus providing a new and versatile tool for algal research.
View details for DOI 10.1073/pnas.1202509109
View details for Web of Science ID 000307807000027
View details for PubMedID 22847404
View details for PubMedCentralID PMC3421176
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Bryostatin analogue-induced apoptosis in mantle cell lymphoma cell lines
EXPERIMENTAL HEMATOLOGY
2012; 40 (8): 646-656
Abstract
The anti-cancer effects of bryostatin-1, a potent diacylglycerol analogue, have traditionally been attributed to its action on protein kinase C. However, we previously documented apoptosis in a B non-Hodgkin lymphoma cell line involving diacylglycerol analogue stimulation of Ras guanyl-releasing protein, a Ras activator, and Bim, a proapoptotic Bcl-2 family protein. To further explore the role of Bim, we examined several Bim-deficient B non-Hodgkin lymphoma cells for their responses to pico, a synthetic bryostatin-1-like compound. The Bim(-) mantle cell lymphoma cell lines Jeko-1, Mino, Sp53, UPN1, and Z138 and the Bim(+) cell line Rec-1, as well as the Burkitt lymphoma cells lines BL2 (Bim(-)) and Daudi (Bim(+)), were examined for their response to pico using assays for proliferation and apoptosis as well as biochemical methods for Ras guanyl-releasing proteins and Bcl-2 family members. With the exception of UPN1, mantle cell lymphoma cell lines underwent pico-induced apoptosis, as did BL2. In some cases, hallmarks of apoptosis were substantially diminished in the presence of mitogen-activated protein kinase kinase inhibitors. Pico treatment generally led to increased expression of proapoptotic Bik, although the absolute levels of Bik varied considerably between cell lines. A pico-resistant variant of Z138 exhibited decreased Bik induction compared to parental Z138 cells. Pico also generally decreased expression of anti-apoptotic Bcl-XL and Mcl1. Although, these changes in Bcl-2 family members seem unlikely to fully account for the differential behavior of the cell lines, our demonstration of a potent apoptotic process in most cell lines derived from mantle cell lymphoma encourages a re-examination of diacylglycerol analogues in the treatment of this subset of B non-Hodgkin lymphoma cases.
View details for DOI 10.1016/j.exphem.2012.03.002
View details for Web of Science ID 000307319500005
View details for PubMedID 22465296
View details for PubMedCentralID PMC4059058
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Ligand Effects on Rates and Regioselectivities of Rh(I)-Catalyzed (5+2) Cycloadditions: A Computational Study of Cyclooctadiene and Dinaphthocyclooctatetraene as Ligands
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2012; 134 (26): 11012-11025
Abstract
The first theoretical study on the effects of ligands on the mechanism, reactivities, and regioselectivities of Rh(I)-catalyzed (5 + 2) cycloadditions of vinylcyclopropanes (VCPs) and alkynes has been performed using density functional theory (DFT) calculations. Highly efficient and selective intermolecular (5 + 2) cycloadditions of VCPs and alkynes have been achieved recently using two novel rhodium catalysts, [Rh(dnCOT)](+)SbF(6)(-) and [Rh(COD)](+)SbF(6)(-), which provide superior reactivities and regioselectivities relative to that of the previously reported [Rh(CO)(2)Cl](2) catalyst. Computationally, the high reactivities of the dnCOT and COD ligands are attributed to the steric repulsions that destabilize the Rh-product complex, the catalyst resting state in the catalytic cycle. The regioselectivities of reactions with various alkynes and different Rh catalysts are investigated, and a predictive model is provided that describes substrate-substrate and ligand-substrate steric repulsions, electronic effects, and noncovalent π/π and C-H/π interactions. In the reactions with dnCOT or COD ligands, the first new C-C bond is formed proximal to the bulky substituent on the alkyne to avoid ligand-substrate steric repulsions. This regioselectivity is reversed either by employing the smaller [Rh(CO)(2)Cl](2) catalyst to diminish the ligand-substrate repulsions or by using aryl alkynes, for which the ligand-substrate interactions become stabilizing due to π/π and C-H/π dispersion interactions. Electron-withdrawing groups on the alkyne prefer to be proximal to the first new C-C bond to maximize metal-substrate back-bonding interactions. These steric, electronic, and dispersion effects can all be utilized in designing new ligands to provide regiochemical control over product formation with high selectivities. The computational studies reveal the potential of employing the dnCOT family of ligands to achieve unique regiochemical control due to the steric influences and dispersion interactions associated with the rigid aryl substituents on the ligand.
View details for DOI 10.1021/ja3041724
View details for Web of Science ID 000305863900049
View details for PubMedID 22668243
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Taxol-oligoarginine conjugates overcome drug resistance in-vitro in human ovarian carcinoma
GYNECOLOGIC ONCOLOGY
2012; 126 (1): 118-123
Abstract
Multidrug resistance is the major cause of failure of many chemotherapeutic agents. While resistance can arise from several factors, it is often dominated by drug efflux mediated by P-glycoprotein (P-gp), a membrane-bound polysubstrate export pump expressed at high levels in resistant cells. While co-administration of pump inhibitors and a drug could suppress efflux, this two-drug strategy has not yet advanced to therapy. We recently demonstrated that the reversible attachment of a guanidinium-rich molecular transporter, polyarginine, to a drug provides a conjugate that overcomes efflux-based resistance in cells and animals. This study is to determine whether this strategy for overcoming resistance is effective against human disease.Tumor samples from ovarian cancer patients, both malignant ascites cells and dissociated solid tumor cells, were exposed to Taxol-oligoarginine conjugates designed to release free drug only after cell entry. Cell viability was determined via propidium-iodide uptake by flow cytometry. To analyze bystander effect, toxicity of the drug conjugates was also tested on peripheral blood leucocytes.Human ovarian carcinoma specimens resistant to Taxol in vitro demonstrated increased sensitivity to killing by all Taxol-transporter conjugates tested. These studies also show that the drug conjugates were not significantly more toxic to normal human peripheral blood leukocytes than Taxol.These studies with human tumor indicate that oligoarginine conjugates of known drugs can be used to overcome the efflux-based resistance to the drug, providing a strategy that could improve the treatment outcomes of patients with efflux-based drug-resistance.
View details for DOI 10.1016/j.ygyno.2012.03.049
View details for Web of Science ID 000305878400023
View details for PubMedID 22484398
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siRNA complexation, delivery, and release by new biodegradable molecular transporters
AMER CHEMICAL SOC. 2012
View details for Web of Science ID 000324503202246
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Beyond Cell Penetrating Peptides: Designed Molecular Transporters.
Drug discovery today. Technologies
2012; 9 (1): e49-e55
Abstract
Inspired originally by peptides that traverse biological barriers, research on molecular transporters has since identified the key structural requirements that govern cellular entry, leading to new, significantly more effective and more readily available agents. These new drug delivery systems enable or enhance cellular and tissue uptake, can be targeted, and provide numerous additional advantages of significance in imaging, diagnostics and therapy.
View details for PubMedID 22712022
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Rhodium Dinaphthocyclooctatetraene Complexes: Synthesis, Characterization and Catalytic Activity in [5+2] Cycloadditions
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2012; 51 (11): 2736-2740
Abstract
Rh COT in the act: a Ni(0)-catalyzed [2+2+2+2] cycloaddition provides a high-yielding, scalable synthesis of the ligand dinaphtho[a,e]cyclooctatetraene (dnCOT). dnCOT complexation with Rh(I) gives [Rh(dnCOT)(MeCN)(2)]SbF(6), an excellent catalyst for [5+2] cycloadditions of vinylcyclopropanes and π-systems with impressive functional group compatibility.
View details for DOI 10.1002/anie.201108270
View details for Web of Science ID 000301173800038
View details for PubMedID 22298411
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Strategies and Tactics in Organic Synthesis Volume 8 Foreword
STRATEGIES AND TACTICS IN ORGANIC SYNTHESIS, VOL 8
2012; 8: XV-XVI
View details for Web of Science ID 000322958700001
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Beyond cell penetrating peptides: designed molecular transporters.
Drug discovery today. Technologies
2012; 9 (1): e1-e70
View details for DOI 10.1016/j.ddtec.2011.07.004
View details for PubMedID 24064244
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"Picolog," a Synthetically-Available Bryostatin Analog, Inhibits Growth of MYC-Induced Lymphoma In Vivo
ONCOTARGET
2012; 3 (1): 58-66
Abstract
Bryostatin 1 is a naturally occurring complex macrolide with potent anti-neoplastic activity. However, its extremely low natural occurrence has impeded clinical advancement. We developed a strategy directed at the design of simplified and synthetically more accessible bryostatin analogs. Our lead analog, "picolog", can be step-economically produced. Picolog, compared to bryostatin, exhibited superior growth inhibition of MYC-induced lymphoma in vitro. A key mechanism of picolog's (and bryostatin's) activity is activation of PKC. A novel nano-immunoassay (NIA) revealed that picolog treatment increased phospho-MEK2 in the PKC pathway. Moreover, the inhibition of PKC abrogated picolog's activity. Finally, picolog was highly potent at 100 micrograms/kg and well tolerated at doses ranging from 100 micrograms/kg to 1 milligram/kg in vivo for the treatment of our aggressive model of MYC-induced lymphoma. We provide the first in vivo validation that the bryostatin analog, picolog, is a potential therapeutic agent for the treatment of cancer and other diseases.
View details for PubMedID 22308267
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Function oriented synthesis: preparation and initial biological evaluation of new A-ring-modified bryologs
TETRAHEDRON
2011; 67 (51): 9998-10005
Abstract
The synthesis and biological evaluation of the first members of a new series of designed bryostatin A-ring analogues (bryologs) are described. An advanced intermediate is produced that allows for step economical access to diverse analogs. The first of these analogues, bearing side chains of completely different polarities from alkyl to hydroxyl and carboxyl functionalities, were evaluated. All exhibit potent protein kinase C binding (54.7 to 2.4 nM) with affinities increasing with decreasing side chain polarity. This series of bryostatin analogues demonstrates that A ring surrogates can indeed be used for tuning pharmacophore and ADME characteristics as needed to improve bryolog function.
View details for DOI 10.1016/j.tet.2011.09.058
View details for Web of Science ID 000298027400024
View details for PubMedCentralID PMC3254100
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Function Oriented Synthesis: Preparation and Initial Biological Evaluation of New A-Ring-Modified Bryologs.
Tetrahedron
2011; 67 (51): 9998-10005
Abstract
The synthesis and biological evaluation of the first members of a new series of designed bryostatin A-ring analogues (bryologs) are described. An advanced intermediate is produced that allows for step economical access to diverse analogs. The first of these analogues, bearing side chains of completely different polarities from alkyl to hydroxyl and carboxyl functionalities, were evaluated. All exhibit potent protein kinase C binding (54.7 to 2.4 nM) with affinities increasing with decreasing side chain polarity. This series of bryostatin analogues demonstrates that A ring surrogates can indeed be used for tuning pharmacophore and ADME characteristics as needed to improve bryolog function.
View details for DOI 10.1016/j.tet.2011.09.058
View details for PubMedID 22247574
View details for PubMedCentralID PMC3254100
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Gateway synthesis of daphnane congeners and their protein kinase C affinities and cell-growth activities
NATURE CHEMISTRY
2011; 3 (8): 615-619
Abstract
The daphnane diterpene orthoesters constitute a structurally fascinating family of natural products that exhibit a remarkable range of potent biological activities. Although partial activity information is available for some natural daphnanes, little information exists for non-natural congeners or on how changes in structure affect mode of action, function, potency or selectivity. A gateway strategy designed to provide general synthetic access to natural and non-natural daphnanes is described and utilized in the synthesis of two novel members of this class. In this study, a commercially available tartrate derivative was elaborated through a key late-stage diversification intermediate into B-ring yuanhuapin analogues to initiate exploration of the structure-function relationships of this class. Protein kinase C was identified as a cellular target for these agents, and their activity against human lung and leukaemia cell lines was evaluated. The natural product and a novel non-natural analogue exhibited significant potency, but the epimeric epoxide was essentially inactive.
View details for DOI 10.1038/NCHEM.1074
View details for Web of Science ID 000292999100014
View details for PubMedID 21778981
View details for PubMedCentralID PMC3144521
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To Eun Lee on His 65th Birthday
CHEMISTRY-AN ASIAN JOURNAL
2011; 6 (8): 1899-1901
View details for DOI 10.1002/asia.201100574
View details for Web of Science ID 000294112200001
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Total Synthesis of Bryostatin 9
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2011; 133 (24): 9228-9231
Abstract
The total synthesis of bryostatin 9 was accomplished using a uniquely step-economical and convergent Prins-driven macrocyclization strategy. At 25 linear and 42 total steps, this is currently the most concise and convergent synthesis of a potent bryostatin.
View details for DOI 10.1021/ja203034k
View details for Web of Science ID 000291915100025
View details for PubMedID 21618969
View details for PubMedCentralID PMC3129979
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Design, synthesis, and evaluation of potent bryostatin analogs that modulate PKC translocation selectivity
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2011; 108 (17): 6721-6726
Abstract
Modern methods for the identification of therapeutic leads include chemical or virtual screening of compound libraries. Nature's library represents a vast and diverse source of leads, often exhibiting exquisite biological activities. However, the advancement of natural product leads into the clinic is often impeded by their scarcity, complexity, and nonoptimal properties or efficacy as well as the challenges associated with their synthesis or modification. Function-oriented synthesis represents a strategy to address these issues through the design of simpler and therefore synthetically more accessible analogs that incorporate the activity-determining features of the natural product leads. This study illustrates the application of this strategy to the design and synthesis of functional analogs of the bryostatin marine natural products. It is specifically directed at exploring the activity-determining role of bryostatin A-ring functionality on PKC affinity and selectivity. The resultant functional analogs, which were prepared by a flexible, modular synthetic strategy, exhibit excellent affinity to PKC and differential isoform selectivity. These and related studies provide the basic information needed for the design of simplified and thus synthetically more accessible functional analogs that target PKC isoforms, major targets of therapeutic interest.
View details for DOI 10.1073/pnas.1015270108
View details for Web of Science ID 000289888500012
View details for PubMedID 21415363
View details for PubMedCentralID PMC3084132
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Translating Nature's Library: The Bryostatins and Function-Oriented Synthesis
ISRAEL JOURNAL OF CHEMISTRY
2011; 51 (3-4): 453-472
Abstract
We review in part our computational, design, synthesis, and biological studies on a remarkable class of compounds and their designed analogs that have led to preclinical candidates for the treatment of cancer, a first-in-class approach to Alzheimer's disease, and a promising strategy to eradicate HIV/AIDS. Because these leads target, in part, protein kinase C (PKC) isozymes, they have therapeutic potential even beyond this striking set of therapeutic indications. This program has given rise to new synthetic methodology and represents an increasingly important direction of synthesis focused on achieving function through synthesis-informed design (function-oriented synthesis).
View details for DOI 10.1002/ijch.201100020
View details for Web of Science ID 000290380100012
View details for PubMedCentralID PMC3364006
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Translating Nature's Library: The Bryostatins and Function-Oriented Synthesis.
Israel journal of chemistry
2011; 51 (3-4): 453-472
Abstract
We review in part our computational, design, synthesis, and biological studies on a remarkable class of compounds and their designed analogs that have led to preclinical candidates for the treatment of cancer, a first-in-class approach to Alzheimer's disease, and a promising strategy to eradicate HIV/AIDS. Because these leads target, in part, protein kinase C (PKC) isozymes, they have therapeutic potential even beyond this striking set of therapeutic indications. This program has given rise to new synthetic methodology and represents an increasingly important direction of synthesis focused on achieving function through synthesis-informed design (function-oriented synthesis).
View details for DOI 10.1002/ijch.201100020
View details for PubMedID 22661768
View details for PubMedCentralID PMC3364006
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What lies ahead
NATURE
2011; 469 (7328): 23–25
View details for Web of Science ID 000285921600011
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THE PREPARATION OF CYCLOHEPT-4-ENONES BY RHODIUM-CATALYZED INTERMOLECULAR [5+2] CYCLOADDITION
ORGANIC SYNTHESES
2011; 88: 109-+
View details for DOI 10.15227/orgsyn.088.0109
View details for Web of Science ID 000211694900012
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Electronic and Steric Control of Regioselectivities in Rh(I)-Catalyzed (5+2) Cycloadditions: Experiment and Theory
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2010; 132 (29): 10127-10135
Abstract
The first studies on the regioselectivity of Rh(I)-catalyzed (5 + 2) cycloadditions between vinylcyclopropanes (VCPs) and alkynes have been conducted experimentally and analyzed using density functional theory (DFT). The previously unexplored regiochemical consequences for this catalytic, intermolecular cycloaddition were determined by studying the reactions of several substituted VCPs with a range of unsymmetrical alkynes. Experimental trends were identified, and a predictive model was established. VCPs with terminal substitution on the alkene reacted with high regioselectivity (>20:1), as predicted by a theoretical model in which bulkier alkyne substituents prefer to be distal to the forming C-C bond to avoid steric repulsions. VCPs with substitution at the internal position of the alkene reacted with variable regioselectivity (ranging from >20:1 to a reversed 1:2.3), suggesting a refined model in which electron-withdrawing substituents on the alkyne decrease or reverse sterically controlled selectivity by stabilizing the transition state in which the substituent is proximal to the forming C-C bond.
View details for DOI 10.1021/ja103253d
View details for Web of Science ID 000280227700048
View details for PubMedID 20586494
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Highly Efficient, Facile, Room Temperature Intermolecular [5+2] Cycloadditions Catalyzed by Cationic Rhodium(I): One Step to Cycloheptenes and Their Libraries
ORGANIC LETTERS
2010; 12 (7): 1604-1607
Abstract
A cationic rhodium(I) complex--[(C(10)H(8))Rh(cod)](+) SbF(6)(-)--catalyzes the remarkably efficient intermolecular [5 + 2] cycloaddition of vinylcyclopropanes (VCPs) and various alkynes, providing cycloheptene cycloadducts in excellent yields in minutes at room temperature. The efficacy and selectivity of this catalyst are also shown in a novel diversification strategy, affording a cycloadduct library in one step from nine commercially available components.
View details for DOI 10.1021/ol100337m
View details for Web of Science ID 000275885400058
View details for PubMedID 20196579
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Special delivery: One-step oligomerization of oligocarbonate molecular transporters and biological evaluation of uptake and delivery
AMER CHEMICAL SOC. 2010
View details for Web of Science ID 000208189303799
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Metal-catalyzed [5+2] cycloadditions: Experimental and theoretical studies on regioselectivity and a new highly efficient catalyst
AMER CHEMICAL SOC. 2010
View details for Web of Science ID 000208189303697
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A Metal-Catalyzed Intermolecular [5+2] Cycloaddition/Nazarov Cyclization Sequence and Cascade
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2010; 132 (8): 2532-?
Abstract
The bicyclo[5.3.0]decane skeleton is one of the most commonly encountered bicyclic subunits in nature and the core scaffold of a wide range of targets of structural, biological, and therapeutic importance. Prompted by the interest in such structures, we report the first studies of metal-catalyzed [5+2] cycloadditions of vinylcyclopropanes (VCPs) and enynones. The resultant efficiently formed dienone cycloadducts serve as substrates for subsequent Nazarov cyclizations and as intermediates for single-operation [5+2]/Nazarov serial reactions and catalytic cascades. In many cases the one-flask process can be carried out in shorter reaction times and with comparable or superior yields to the two-flask procedure. Significantly, a single catalyst can be used to mediate both transformations. These [5+2]/Nazarov reaction sequences and cascades collectively provide strategically novel and facile access to the bicyclo[5.3.0]decane skeleton from simple and readily available components.
View details for DOI 10.1021/ja910696x
View details for Web of Science ID 000275117900021
View details for PubMedID 20141136
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The Diene Effect: The Design, Development, and Mechanistic Investigation of Metal-Catalyzed Diene-yne, Diene-ene, and Diene-allene [2+2+1] Cycloaddition Reactions
EUROPEAN JOURNAL OF ORGANIC CHEMISTRY
2010: 19-32
View details for DOI 10.1002/ejoc.200900929
View details for Web of Science ID 000273774500001
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Apoptolidins E and F, New Glycosylated Macrolactones Isolated from Nocardiopsis sp.
ORGANIC LETTERS
2009; 11 (23): 5474-5477
Abstract
Two new glycosylated macrolactones, apoptolidins E (5) and F (6), were isolated from fermentation of the actinomycete Nocardiopsis sp. and their structures assigned. Lacking the C16 and C20 oxygens of apoptolidin A (1), these macrolides are also the first members of this family to display a 4-O-methyl-l-rhamnose at C9 rather than a 6-deoxy-4-O-methyl-l-glucose.
View details for DOI 10.1021/ol902308v
View details for Web of Science ID 000272038200029
View details for PubMedID 19943700
View details for PubMedCentralID PMC2789431
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Oligocarbonate Molecular Transporters: Oligomerization-Based Syntheses and Cell-Penetrating Studies
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2009; 131 (45): 16401-?
Abstract
A new family of guanidinium-rich molecular transporters featuring a novel oligocarbonate backbone with 1,7-side chain spacing is described. Conjugates can be rapidly assembled irrespective of length in a one-step oligomerization strategy that can proceed with concomitant introduction of probes (or by analogy drugs). The new transporters exhibit excellent cellular entry as determined by flow cytometry and fluorescence microscopy, and the functionality of their drug delivery capabilities was confirmed by the delivery of the bioluminescent small molecule probe luciferin and turnover by its intracellular target enzyme.
View details for DOI 10.1021/ja907363k
View details for Web of Science ID 000271723000030
View details for PubMedID 19860416
View details for PubMedCentralID PMC2789006
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Prolonging microtubule dysruption enhances the immunogenicity of chronic lymphocytic leukaemia cells
CLINICAL AND EXPERIMENTAL IMMUNOLOGY
2009; 158 (2): 186-198
Abstract
Cytotoxic chemotherapies do not usually mediate the expression of an immunogenic gene programme in tumours, despite activating many of the signalling pathways employed by highly immunogenic cells. Concomitant use of agents that modulate and complement stress-signalling pathways activated by chemotherapeutic agents may then enhance the immunogenicity of cancer cells, increase their susceptibility to T cell-mediated controls and lead to higher clinical remission rates. Consistent with this hypothesis, the microtubule inhibitor, vincristine, caused chronic lymphocytic leukaemia (CLL) cells to die rapidly, without increasing their immunogenicity. Protein kinase C (PKC) agonists (such as bryostatin) delayed the death of vincristine-treated CLL cells and made them highly immunogenic, with increased stimulatory abilities in mixed lymphocyte responses, production of proinflammatory cytokines, expression of co-stimulatory molecules and activation of c-Jun N-terminal kinase (JNK), p38 and nuclear factor kappa B (NF-kappaB) signalling pathways. This phenotype was similar to the result of activating CLL cells through Toll-like receptors (TLRs), which communicate 'danger' signals from infectious pathogens. Use of PKC agonists and microtubule inhibitors to mimic TLR-signalling, and increase the immunogenicity of CLL cells, has implications for the design of chemo-immunotherapeutic strategies.
View details for DOI 10.1111/j.1365-2249.2009.04003.x
View details for Web of Science ID 000270397000004
View details for PubMedID 19737143
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Rhodium(I)-Catalyzed [2+2], [2+2+2], and [2+2+2+2] Cycloadditions of Dienes or Alkynes with a Bis-ene
ORGANOMETALLICS
2009; 28 (20): 5841-5844
View details for DOI 10.1021/om9007373
View details for Web of Science ID 000270789200002
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An Approach to the Site-Selective Diversification of Apoptolidin A with Peptide-Based Catalysts
JOURNAL OF NATURAL PRODUCTS
2009; 72 (10): 1864-1869
Abstract
We report the application of peptide-based catalysts to the site-selective modification of apoptolidin A (1), an agent that displays remarkable selectivity for inducing apoptosis in E1A-transformed cell lines. Key to the approach was the development of an assay suitable for the screening of dozens of catalysts in parallel reactions that could be conducted using only microgram quantities of the starting material. Employing this assay, catalysts (e.g., 11 and ent-11) were identified that afforded unique product distributions, distinct from the product mixtures produced when a simple catalyst (N,N-dimethyl-4-aminopyridine (10)) was employed. Preparative reactions were then carried out with the preferred catalysts so that unique, homogeneous apoptolidin analogues could be isolated and characterized. From these studies, three new apoptolidin analogues were obtained (12-14), each differing from the other in either the location of acyl group substituents or the number of acetate groups appended to the natural product scaffold. Biological evaluation of the new apoptolidin analogues was then conducted using growth inhibition assays based on the H292 human lung carcinoma cell line. The new analogues exhibited activities comparable to apoptolidin A.
View details for DOI 10.1021/np9004932
View details for Web of Science ID 000271950400022
View details for PubMedID 19769383
View details for PubMedCentralID PMC2857549
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Design and development of rhodium(I)-catalyzed cycloadditions and synthesis of designed Amphotericin B analogs
AMER CHEMICAL SOC. 2009: 57
View details for Web of Science ID 000207861900056
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Synthesis at the molecular frontier
NATURE
2009; 460 (7252): 197-201
View details for DOI 10.1038/460197a
View details for Web of Science ID 000267761000029
View details for PubMedID 19587760
View details for PubMedCentralID PMC2857510
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Cyclocarboamination of Alkynes with Aziridines: Synthesis of 2,3-Dihydropyrroles by a Catalyzed Formal [3+2] Cycloaddition
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2009; 131 (22): 7528-?
Abstract
An efficient cyclocarboamination reaction of nonactivated alkynes with aziridines, catalyzed by Lewis or Bronsted acids, to form 2,3-dihydropyrroles through a formal [3+2] cycloaddition, is described. The reaction provides a wide range of polysubstituted dihydropyrroles in a highly regioselective manner, is scalable, proceeds under mild reaction conditions, and uses low catalyst loadings.
View details for DOI 10.1021/ja901799s
View details for Web of Science ID 000267177900025
View details for PubMedID 19489638
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A cellular model of Alzheimer's disease therapeutic efficacy: PKC activation reverses A beta-induced biomarker abnormality on cultured fibroblasts
NEUROBIOLOGY OF DISEASE
2009; 34 (2): 332-339
Abstract
PKC signaling is critical for the non-toxic degradation of amyloid precursor protein (APP) and inhibition of GSK3beta, which controls phosphorylation of tau protein in Alzheimer's disease (AD). Thus the misregulation of PKC signaling could contribute to the origins of AD. Bryostatin, a potent PKC modulator, has the potential to ameliorate both the neurodegeneration and the recent memory loss associated with AD. As reported herein bryostatin and a potent synthetic analog (picolog) are found to cause stimulation of non-amyloidogenic pathways by increasing alpha-secretase activity and thus lowering the amount of toxic Abeta produced. Both bryostatin and picolog increased the secretion of the alpha-secretase product (s-APP-alpha) of APP at sub-nanomolar to nanomolar concentrations. A peripheral AD-Biomarker has previously been autopsy-validated. This Biomarker, based on bradykinin-induced differential phosphorylation of Erk1 and Erk2, has been used here to test the therapeutic efficacy both for bryostatin and picolog. Both of these PKC activators are then shown to convert the AD Erk1/2 phenotype of fibroblasts into the phenotype of "normal" control skin fibroblasts. This conversion occurred for both the abnormal Erk1/2 phenotype induced by application of Abeta(1-42) to the fibroblasts or the phenotype observed for fibroblasts of AD patients. The Abeta(1-42)-induction, and PKC modulator reversal of the AD Erk1/2 biomarker phenotype demonstrate the AD-Biomarker's potential to monitor both disease progression and treatment response. Additionally, this first demonstration of the therapeutic potential in AD of a synthetically accessible bryostatin analog warrants further preclinical advancement.
View details for DOI 10.1016/j.nbd.2009.02.003
View details for Web of Science ID 000265869400014
View details for PubMedID 19233276
View details for PubMedCentralID PMC2683973
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The Synthesis of Highly Substituted Cyclooctatetraene Scaffolds by Metal-Catalyzed [2+2+2+2] Cycloadditions: Studies on Regioselectivity, Dynamic Properties, and Metal Chelation
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2009; 48 (41): 7687-7690
View details for DOI 10.1002/anie.200903859
View details for Web of Science ID 000270436900041
View details for PubMedID 19739178
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A proapoptotic signaling pathway involving RasGRP, Erk, and Bim in B cells
EXPERIMENTAL HEMATOLOGY
2009; 37 (1): 122-134
Abstract
Bryostatin-1 and related diacylglycerol (DAG) analogues activate RasGRPs in lymphocytes, thereby activating Ras and mimicking some aspects of immune receptor signaling. To define the role of RasGRPs in lymphocyte apoptosis and to identify potential therapeutic uses for DAG analogues in lymphocyte disorders, we characterized the response of lymphoma-derived cell lines to DAG analogues.Human lymphoma-derived B cell lines and mouse primary B cells were treated with bryostatin-1 or its synthetic analogue "pico." Ras signaling partners and Bcl-2 family members were studied with biochemical assays. Cellular responses were monitored using growth and apoptosis assays.Stimulation of B cells with DAG analogues results in activation of protein kinase C/RasGRP-Ras-Raf-Mek-Erk signaling and phosphorylation of the proapoptotic BH3-only protein Bim. In vitro, Bim is phosphorylated by Erk on sites previously associated with increased apoptotic activity. In Toledo B cells derived from a non-Hodgkin's lymphoma (B-NHL), DAG analogue stimulation leads to extensive apoptosis. Apoptosis can be suppressed by either downregulation of Bim or overexpression of Bcl-2. It is associated with the formation of Bak-Bax complexes and increased mitochondrial membrane permeability. Toledo B-NHL cell apoptosis shows a striking dependence on sustained signaling.In B cells, Erk activation leads directly to phosphorylation of Bim on sites associated with activation of Bim. In Toledo B-NHL cells, the dependence of apoptosis on sustained signaling suggests that Bcl-2 family members could interpret signal duration, an important determinant of B cell receptor-mediated negative selection. Certain cases of B-NHL might respond to DAG analogue treatment by the mechanism outlined here.
View details for DOI 10.1016/j.exphem.2008.09.008
View details for Web of Science ID 000262216400014
View details for PubMedID 19100522
View details for PubMedCentralID PMC2708980
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Function-oriented synthesis: Biological evaluation of laulimalide analogues derived from a last step cross metathesis diversification strategy
MOLECULAR PHARMACEUTICS
2008; 5 (5): 829-838
Abstract
Laulimalide is a potent microtubule stabilizing agent and a promising anticancer therapeutic lead. The identification of stable, efficacious and accessible analogues is critical to clinically exploiting this novel lead. To determine which structural features of laulimalide are required for beneficial function and thus for accessing superior clinical candidates, a series of side chain analogues were prepared through a last step cross metathesis diversification strategy and their biological activities were evaluated. Five analogues, differing in potency from 233 nM to 7.9 muM, effectively inhibit cancer cell proliferation. Like laulimalide, they retain activity against multidrug resistant cells, stabilize microtubules and cause the formation of aberrant mitotic spindles, mitotic accumulation, Bcl-2 phosphorylation and initiation of apoptosis. Structural modifications in the C 23-C 27 dihydropyran side chain can be made without changing the overall mechanism of action, but it is clear that this subunit has more than a bystander role.
View details for DOI 10.1021/mp800043n
View details for Web of Science ID 000259859500014
View details for PubMedID 18662015
View details for PubMedCentralID PMC2676913
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Overcoming multidrug resistance of small-molecule therapeutics through conjugation with releasable octaarginine transporters
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2008; 105 (34): 12128-12133
Abstract
Many cancer therapeutic agents elicit resistance that renders them ineffective and often produces cross-resistance to other drugs. One of the most common mechanisms of resistance involves P-glycoprotein (Pgp)-mediated drug efflux. To address this problem, new agents have been sought that are less prone to inducing resistance and less likely to serve as substrates for Pgp efflux. An alternative to this approach is to deliver established agents as molecular transporter conjugates into cells through a mechanism that circumvents Pgp-mediated efflux and allows for release of free drug only after cell entry. Here we report that the widely used chemotherapeutic agent Taxol, ineffective against Taxol-resistant human ovarian cancer cell lines, can be incorporated into a releasable octaarginine conjugate that is effective against the same Taxol-resistant cell lines. It is significant that the ability of the Taxol conjugates to overcome Taxol resistance is observed both in cell culture and in animal models of ovarian cancer. The generality and mechanistic basis for this effect were also explored with coelenterazine, a Pgp substrate. Although coelenterazine itself does not enter cells because of Pgp efflux, its octaarginine conjugate does so readily. This approach shows generality for overcoming the multidrug resistance elicited by small-molecule cancer chemotherapeutics and could improve the prognosis for many patients with cancer and fundamentally alter search strategies for novel therapeutic agents that are effective against resistant disease.
View details for DOI 10.1073/pnas.0805374105
View details for Web of Science ID 000258905700008
View details for PubMedID 18713866
View details for PubMedCentralID PMC2527877
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The design, synthesis, and evaluation of C7 diversified bryostatin analogs reveals a hot spot for PKC affinity
ORGANIC LETTERS
2008; 10 (15): 3331-3334
Abstract
The first series of systematically varied C7-functionalized bryostatin analogs (12 members in all) have been synthesized through an efficient and convergent route. A new hotspot for PKC affinity, not present in the natural products, has been discovered, allowing for affinity control and potentially for selective regulation of PKC isozymes. Several analogs exhibit single-digit nanomolar affinity to PKC and display superior activity compared to bryostatin against the leukemia cell line K562.
View details for DOI 10.1021/ol801235h
View details for Web of Science ID 000257955100041
View details for PubMedID 18588309
View details for PubMedCentralID PMC2730840
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Single-molecule motions of oligoarginine transporter conjugates on the plasma membrane of Chinese hamster ovary cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2008; 130 (29): 9364-9370
Abstract
To explore the real-time dynamic behavior of molecular transporters of the cell-penetrating-peptide (CPP) type on a biological membrane, single fluorescently labeled oligoarginine conjugates were imaged interacting with the plasma membrane of Chinese hamster ovary (CHO) cells. The diffusional motion on the membrane, characterized by single-molecule diffusion coefficient and residence time (tau R), defined as the time from the initial appearance of a single-molecule spot on the membrane (from the solution) to the time the single molecule disappears from the imaging focal plane, was observed for a fluorophore-labeled octaarginine (a model guanidinium-rich CPP) and compared with the corresponding values observed for a tetraarginine conjugate (negative control), a lipid analogue, and a fluorescently labeled protein conjugate (transferrin-Alexa594) known to enter the cell through endocytosis. Imaging of the oligoarginine conjugates was enabled by the use of a new high-contrast fluorophore in the dicyanomethylenedihydrofuran family, which brightens upon interaction with the membrane at normal oxygen concentrations. Taken as a whole, the motions of the octaarginine conjugate single molecules are highly heterogeneous and cannot be described as Brownian motion with a single diffusion coefficient. The observed behavior is also different from that of lipids, known to penetrate cellular membranes through passive diffusion, conventionally involving lateral diffusion followed by membrane bilayer flip-flop. Furthermore, while the octaarginine conjugate behavior shares some common features with transferrin uptake (endocytotic) processes, the two systems also exhibit dissimilar traits when diffusional motions and residence times of single constructs are compared. Additionally, pretreatment of cells with cytochalasin D, a known actin filament disruptor, produces no significant effect, which further rules out unimodal endocytosis as the mechanism of uptake. Also, the involvement of membrane potential in octaarginine-membrane interaction is supported by significant changes in the motion with high [K(+)] treatment. In sum, this first study of single transporter motion on the membrane of a living cell indicates that the mode by which the octaarginine transporter penetrates the cell membrane appears to either be a multimechanism uptake process or a mechanism different from unimodal passive diffusion or endocytosis.
View details for DOI 10.1021/ja710798b
View details for PubMedID 18578528
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Efficient synthetic access to a new family of highly potent bryostatin analogues via a prins-driven macrocyclization strategy
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2008; 130 (21): 6658-?
Abstract
The step-economical synthesis of a new class of bryostatin analogues that contain the complete oxycarbocyclic core ring system of the bryostatin natural products is reported. These agents are convergently assembled via a highly efficient, functional-group-tolerant, and stereoselective Prins-driven macrocyclization. These tetrahydropyranyl B-ring analogues are among our most potent and efficacious analogues to date, exhibiting nanomolar and picomolar activities in protein kinase C affinity assays as well as in cellular antiproliferation assays.
View details for DOI 10.1021/ja8015632
View details for Web of Science ID 000256158200003
View details for PubMedID 18452292
View details for PubMedCentralID PMC2681322
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Practical synthesis of prostratin, DPP, and their analogs, adjuvant leads against latent HIV
SCIENCE
2008; 320 (5876): 649-652
Abstract
Although antiretroviral therapies have been effective in decreasing active viral loads in AIDS patients, the persistence of latent viral reservoirs prevents eradication of the virus. Prostratin and DPP (12-deoxyphorbol-13-phenylacetate) activate the latent virus and thus represent promising adjuvants for antiviral therapy. Their limited supply and the challenges of accessing related structures have, however, impeded therapeutic development and the search for clinically superior analogs. Here we report a practical synthesis of prostratin and DPP starting from phorbol or crotophorbolone, agents readily available from renewable sources, including a biodiesel candidate. This synthesis reliably supplies gram quantities of the therapeutically promising natural products, hitherto available only in low and variable amounts from natural sources, and opens access to a variety of new analogs.
View details for DOI 10.1126/science.1154690
View details for Web of Science ID 000255454300041
View details for PubMedID 18451298
View details for PubMedCentralID PMC2704988
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ORGN 694-Theoretical studies on rhodium(I) catalyzed (5+2) cycloadditions
235th American-Chemical-Society National Meeting
AMER CHEMICAL SOC. 2008
View details for Web of Science ID 000271775108342
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The design of guanidinium-rich transporters and their internalization mechanisms
ADVANCED DRUG DELIVERY REVIEWS
2008; 60 (4-5): 452-472
Abstract
The ability of a drug or probe to cross a biological barrier has historically been viewed to be a function of its intrinsic physical properties. This view has largely restricted drug design and selection to agents within a narrow log P range. Molecular transporters offer a strategy to circumvent these restrictions. In the case of guanidinium-rich transporters (GRTs), a typically highly water-soluble conjugate is found to readily pass through the non-polar membrane of a cell and for some across tissue barriers. This activity opens a field of opportunities for the use of GRTs to enable delivery of polar and non-polar drugs or probes as well as to enhance uptake of those of intermediate polarity. The field of transporter enabled or enhanced uptake has grown dramatically in the last decade. Some GRT drug conjugates have been advanced into clinical trials. This review will provide an overview of recent work pertinent to the design and mechanism of uptake of GRTs.
View details for DOI 10.1016/j.addr.2007.10.016
View details for Web of Science ID 000254068000003
View details for PubMedID 18164781
View details for PubMedCentralID PMC2533582
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Origins of differences in reactivities of alkenes, alkynes, and allenes in [Rh(CO)(2)CI](2)-catalyzed (5+2) cycloaddition reactions with vinylcyclopropanes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2008; 130 (8): 2378-2379
View details for DOI 10.1021/ja076444d
View details for Web of Science ID 000253400900003
View details for PubMedID 18251468
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Function-oriented synthesis, step economy, and drug design
ACCOUNTS OF CHEMICAL RESEARCH
2008; 41 (1): 40-49
Abstract
This Account provides an overview and examples of function-oriented synthesis (FOS) and its increasingly important role in producing therapeutic leads that can be made in a step-economical fashion. Biologically active natural product leads often suffer from several deficiencies. Many are scarce or difficult to obtain from natural sources. Often, they are highly complex molecules and thus not amenable to a practical synthesis that would impact supply. Most are not optimally suitable for human therapeutic use. The central principle of FOS is that the function of a biologically active lead structure can be recapitulated, tuned, or greatly enhanced with simpler scaffolds designed for ease of synthesis and also synthetic innovation. This approach can provide practical access to new (designed) structures with novel activities while at the same time allowing for synthetic innovation by target design. This FOS approach has been applied to a number of therapeutically important natural product leads. For example, bryostatin is a unique natural product anticancer lead that restores apoptosis in cancer cells, reverses multidrug resistance, and bolsters the immune system. Remarkably, it also improves cognition and memory in animals. We have designed and synthesized simplified analogs of bryostatin that can be made in a practical fashion (pilot scale) and are superior to bryostatin in numerous assays including growth inhibition in a variety of human cancer cell lines and in animal models. Laulimalide is another exciting anticancer lead that stabilizes microtubules, like paclitaxel, but unlike paclitaxel, it is effective against multidrug-resistant cell lines. Laulimalide suffers from availability and stability problems, issues that have been addressed using FOS through the design and synthesis of stable and efficacious laulimalide analogs. Another FOS program has been directed at the design and synthesis of drug delivery systems for enabling or enhancing the uptake of drugs or drug candidates into cells and tissue. We have generated improved transporters that can deliver agents in a superior fashion compared with naturally occurring cell-penetrating peptides and that can be synthesized in a practical and step-economical fashion. The use of FOS has allowed for the translation of exciting, biologically active natural product leads into simplified analogs with superior function. This approach enables the development of synthetically innovative strategies while targeting therapeutically novel structures.
View details for DOI 10.1021/ar700155p
View details for Web of Science ID 000252419500006
View details for PubMedID 18159936
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Substituent effects, reactant preorganization, and ligand exchange control the reactivity in Rh-I-catalyzed (5+2) cycloadditions between vinylcyclopropanes and alkynes
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2008; 47 (21): 3939-3941
View details for DOI 10.1002/anie.200800420
View details for Web of Science ID 000255994700014
View details for PubMedID 18412215
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Nickel(0)-catalyzed [2+2+2+2] cycloadditions of terminal diynes for the synthesis of substituted cyclooctatetraenes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2007; 129 (44): 13402-?
View details for DOI 10.1021/ja0763044
View details for Web of Science ID 000250819200022
View details for PubMedID 17929819
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N-Alkoxyimidazolylidene transition-metal complexes: Application to [5+2] and [4+2] cycloaddition reactions
ORGANOMETALLICS
2007; 26 (18): 4541-4545
View details for DOI 10.1021/om700493y
View details for Web of Science ID 000248865600026
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A computationally designed Rh(I)-catalyzed two-component [5+2+1] cycloaddition of ene-vinylcyclopropanes and CO for the synthesis of cyclooctenones
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2007; 129 (33): 10060-?
View details for DOI 10.1021/ja072505w
View details for Web of Science ID 000248896400008
View details for PubMedID 17655302
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MEDI 229-Mechanism of the translocation of guanidium-rich peptides into cells
AMER CHEMICAL SOC. 2007
View details for Web of Science ID 000207593906592
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Real-time analysis of uptake and bioactivatable cleavage of luciferin-transporter conjugates in transgenic reporter mice
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2007; 104 (25): 10340-10345
Abstract
Many therapeutic leads fail to advance clinically because of bioavailability, selectivity, and formulation problems. Molecular transporters can be used to address these problems. Molecular transporter conjugates of otherwise poorly soluble or poorly bioavailable drugs or probes exhibit excellent solubility in water and biological fluids and at the same time an enhanced ability to enter tissues and cells and with modification to do so selectively. For many conjugates, however, it is necessary to release the drug/probe cargo from the transporter after uptake to achieve activity. Here, we describe an imaging method that provides quantification of transporter conjugate uptake and cargo release in real-time in animal models. This method uses transgenic (luciferase) reporter mice and whole-body imaging, allowing noninvasive quantification of transporter conjugate uptake and probe (luciferin) release in real time. This process effectively emulates drug-conjugate delivery, drug release, and drug turnover by an intracellular target, providing a facile method to evaluate comparative uptake of new transporters and efficacy and selectivity of linker release as required for fundamental studies and therapeutic applications.
View details for DOI 10.1073/pnas.0703919104
View details for Web of Science ID 000247500000010
View details for PubMedID 17563383
View details for PubMedCentralID PMC1965515
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Function-oriented synthesis: Studies aimed at the synthesis and mode of action of 1 alpha-alkyldaphnane analogues
ORGANIC LETTERS
2007; 9 (9): 1829-1832
Abstract
[reaction: see text] An efficient synthetic route to the ABC tricyclic core of 1alpha-alkyldaphnanes has been developed. The conformational bias imparted by the C6-C9 oxo-bridge of BC-ring system 12 was used to elaborate the ABC-ring system precursor including the introduction of the beta-C5 hydroxyl group. A completely diastereoselective palladium-catalyzed enyne cyclization was then employed to establish the A-ring with a C1 appendage.
View details for DOI 10.1021/ol0705649
View details for Web of Science ID 000245799200054
View details for PubMedID 17408281
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Nature as a teacher: New drug leads, drug delivery systems, and real time in vivo imaging methods
AMER CHEMICAL SOC. 2007: 472
View details for Web of Science ID 000207722804470
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Isolation, structure determination, and anti-cancer activity of apoptolidin D
ORGANIC LETTERS
2007; 9 (4): 691-694
Abstract
The isolation, characterization, and preliminary biological activity of apoptolidin D, a new apoptolidin that exhibits anti-proliferative activity against H292 human lung carcinoma cells at nanomolar concentrations, are reported. Its equilibration with isoapoptolidin D and characterization of the latter are also described. [structure: see text].
View details for DOI 10.1021/ol0630245
View details for Web of Science ID 000244039800037
View details for PubMedID 17286376
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Cyclopentadienone synthesis by rhodium(I)-catalyzed [3+2] cycloaddition reactions of cyclopropenones and alkynes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2006; 128 (46): 14814-14815
Abstract
The Rh(I)-catalyzed [3 + 2] cycloaddition of cyclopropenones and alkynes is found to provide a highly efficient and regiocontrolled route to cyclopentadienones (CPDs), building blocks of widespread use in the synthesis of natural and non-natural products, therapeutic leads, polymers, dendrimers, devices, and antigen presenting scaffolds. The versatility of the method is explored with 23 examples representing a wide range of alkyne variations (arylalkyl-, dialkyl-, heteroarylalkyl-) and diaryl- as well as arylalkylcyclopropenones. The reactions often proceed in high yield using minimal catalyst loadings and in all cases examined proceed with high or complete regioselectivity. The reaction is readily scalable to produce gram quantities of cycloadduct and provides a unique and versatile route to CPDs that would be otherwise difficult to obtain.
View details for DOI 10.1021/ja065868p
View details for Web of Science ID 000242021700040
View details for PubMedID 17105285
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Total synthesis and initial biological evaluation of new B-ring-modified bryostatin analogs
ORGANIC LETTERS
2006; 8 (23): 5299-5302
Abstract
[Structure: see text] The total synthesis and preliminary biological evaluation of the first bryostatin analogs (bryologs) to incorporate B-ring substitution are reported. Asymmetric syntheses of two new polyketide "spacer" domains are described, one exploiting the pseudosymmetry of the C1-C13 region. These fragments are convergently joined to the "recognition" domain through a remarkably versatile macrotransacetalization process. The resulting new analogs exhibit potent nanomolar or picomolar affinity to protein kinase C (PKC), comparable to or better than that found for bryostatin.
View details for DOI 10.1021/ol0620904
View details for Web of Science ID 000241729500031
View details for PubMedID 17078702
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Studies on oxidopyrylium [5+2] cycloadditions: Toward a general synthetic route to the C12-hydroxy daphnetoxins
ORGANIC LETTERS
2006; 8 (23): 5373-5376
Abstract
[Structure: see text] 12-hydroxydaphnetoxins, members of the structurally fascinating daphnane diterpene family, exhibit a wide range of significant biological activities. A general route to the BC-ring system of 12-hydroxy daphnetoxins is reported based on D-ribose. Depending on the choice of protecting groups and solvent, the oxidopyrylium-alkene [5+2] cycloaddition originating from A provides cycloadduct diastereomer B or C with good to excellent selectivity.
View details for DOI 10.1021/ol062234e
View details for Web of Science ID 000241729500050
View details for PubMedID 17078721
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Molecular transporters: Synthesis of oligoguanidinium transporters and their application to drug delivery and real-time imaging
CHEMBIOCHEM
2006; 7 (10): 1497-1515
View details for DOI 10.1002/cbic.200600171
View details for Web of Science ID 000241392400004
View details for PubMedID 16972294
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Synthesis and PKC binding of a new class of A-ring diversifiable bryostatin analogues utilizing a double asymmetric hydrogenation and cross-coupling strategy
ORGANIC LETTERS
2006; 8 (20): 4581-4584
Abstract
The design, asymmetric synthesis, and biological evaluation of a new class of bryostatin analogues based on a pseudosymmetric spacer domain are described. An aryl bromide diversification site is incorporated allowing access to systematically varied analogues. The new analogues all exhibit potent, nanomolar affinity to PKC.
View details for DOI 10.1021/ol0618149
View details for Web of Science ID 000240654700050
View details for PubMedID 16986955
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PHYS 496-Lateral movements of single poly(arginine) peptides on the CHO plasma membrane before cellular entry
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781609163
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MEDI 279-Releasable luciferin-transporter conjugates: Tools for the real time analysis of uptake and release
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781607499
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MEDI 87-Function oriented synthesis: Design, synthesis, and biological evaluation of novel chemotherapeutic agents in the bryolog series
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781607644
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ORGN 713-Progress towards the total synthesis of gnidimacrin: Synthesis of the tricyclic core and macrocycle precursor
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781608507
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ORGN 712-Neurotrophic factors and the treatment of neurodegenerative diseases: Studies on the total synthesis of kirkinine, a uniquely potent neurotrophic agent
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781608513
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ORGN 894-Step economy and the ideal synthesis: The design of new transition metal-catalyzed reactions
AMER CHEMICAL SOC. 2006
View details for Web of Science ID 000207781608633
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Pharmacophore mapping in the laulimalide series: Total synthesis of a vinylogue for a late-stage metathesis diversification strategy
ORGANIC LETTERS
2006; 8 (18): 4105-4108
Abstract
An efficient synthesis of the macrocyclic core of laulimalide with a pendant vinyl group at C20 is described, allowing for late-stage introduction of various side chains through a selective and efficient cross metathesis diversification step. Representative analogues reported herein are the first to contain modifications to only the side chain dihydropyran of laulimalide and des-epoxy laulimalide. This step-economical strategy enables the rapid synthesis of new analogues using alkenes as an inexpensive, abundantly available diversification feedstock.
View details for DOI 10.1021/ol061619u
View details for Web of Science ID 000239990900055
View details for PubMedID 16928085
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New reactions and step economy: the total synthesis of (+/-)-salsolene oxide based on the type II transition metal-catalyzed intramolecular [4+4] cycloaddition
TETRAHEDRON
2006; 62 (32): 7505-7511
View details for DOI 10.1016/j.tet.2006.02.085
View details for Web of Science ID 000239065900002
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Laulimalide and synthetic laulimalide analogues are synergistic with paclitaxel and 2-methoxyestradiol
MOLECULAR PHARMACEUTICS
2006; 3 (4): 457-467
Abstract
Some of the most significant therapeutic leads and agents used for the treatment of cancer target microtubule dynamics. Paclitaxel is an exceptional example that is currently used for treating a wide range of tumors. New, non-taxane microtubule stabilizers, including several epothilones, are advancing through clinical trials. Laulimalide is a potent microtubule stabilizer that binds to tubulin at a site that does not overlap the taxane-binding site. It is active against paclitaxel-resistant cancer cells. Notwithstanding its therapeutic potential, laulimalide is relatively unstable, rearranging to a more stable but less active isomer. The goal of this study was to evaluate the ability of laulimalide and two designed laulimalide analogues, C16-C17-des-epoxy laulimalide (LA1) and C20-methoxy laulimalide (LA2), to inhibit cell proliferation in combination with other tubulin-binding and non-tubulin-binding antiproliferative antimitotic agents. The synthetic laulimalide analogues retain the mechanism of action of the natural compound but do not share its instability. We studied the ability of the laulimalides to act synergistically with paclitaxel, 2-methoxyestradiol, and monastrol, an Eg5 kinesin inhibitor. The results show that all three of the laulimalides acted synergistically with paclitaxel and 2-methoxyestradiol to inhibit proliferation with the analogues exhibiting significantly larger synergistic effects. The combination of laulimalide and monastrol was not synergistic and provided only additive effects. The laulimalide analogues LA1 and LA2 had a greater degree of synergy with both paclitaxel and 2-methoxyestradiol than was observed with laulimalide. Our results show that the laulimalides together with other tubulin-binding antimitotic agents provide synergistic antiproliferative actions. The data are consistent with the previously reported ability of laulimalide and paclitaxel to act synergistically to polymerize tubulin in vitro. These important findings suggest that specific combinations of microtubule-targeting agents should be considered for clinical utilities as they have excellent potential to improve clinical response.
View details for DOI 10.1021/mp060016h
View details for Web of Science ID 000203539600011
View details for PubMedID 16889440
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Releasable luciferin-transporter conjugates: Tools for the real-time analysis of cellular uptake and release
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2006; 128 (20): 6526-6527
Abstract
The design, synthesis, and evaluation of conjugates of arginine-rich transporters and luciferin are described that release luciferin only after entry into cells that are stably transfected with luciferase. Each molecule of free luciferin that is released after entry generates a photon that can be measured allowing for real-time quantification of uptake and release in cells. The process provides a method to assay uptake and release of free luciferin as a function of variations in the releasable linker and in the transporter.
View details for DOI 10.1021/ja0586283
View details for Web of Science ID 000237590500002
View details for PubMedID 16704230
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Asymmetric catalysis of the [5+2] cycloaddition reaction of vinylcyclopropanes and pi-systems
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2006; 128 (19): 6302-6303
Abstract
As part of our studies of metal-catalyzed [m + n (+...o)] cycloadditions, we have previously reported the rhodium-catalyzed [5 + 2] cycloaddition of vinylcyclopropanes (VCPs) and pi-systems. These studies have led to Rh(I) complexes that catalyze these reactions in minutes at room temperature or in water without organic solvents. We describe a comparative evaluation of several chiral catalysts for the [5 + 2] reaction, evaluation of a preferred catalyst, [((R)-BINAP)Rh]+SbF6-, with substrates differing in substitution and tether types-producing enantiomeric excesses >/=95% for several systems. A predictive model for the selectivity is also presented.
View details for DOI 10.1021/ja058590u
View details for Web of Science ID 000237590400017
View details for PubMedID 16683779
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Intracellular cargo delivery by an octaarginine transporter adapted to target prostate cancer cells through cell surface protease activation
BIOCONJUGATE CHEMISTRY
2006; 17 (3): 787-796
Abstract
Delivery of therapeutics and imaging agents to target tissues requires localization and activation strategies with molecular specificity. Cell-associated proteases can be used for these purposes in a number of pathologic conditions, and their enzymatic activities can be exploited for activation strategies. Here, molecules based on the d-arginine octamer (r8) protein-transduction domain (PTD, also referred to as molecular transporters) have been adapted for selective uptake into cells only after proteolytic cleavage of a PTD-attenuating sequence by the prostate-specific antigen (PSA), an extracellular protease associated with the surface and microenvironment of certain prostate cancer cells. Convergent syntheses of these activatable PTDs (APTDs) are described, and the most effective r8 PTD-attenuating sequence is identified. The conjugates are shown to be stable in serum, cleaved by PSA, and taken up into Jurkat (human T cells) and PC3M prostate cancer cell lines only after cleavage by PSA. These APTD peptide-based molecules may facilitate targeted delivery of therapeutics or imaging agents to PSA-expressing prostate cancers.
View details for DOI 10.1021/bc0503216
View details for PubMedID 16704219
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Design, synthesis, and biological evaluation of a potent, PKC selective, B-ring analog of bryostatin
ORGANIC LETTERS
2006; 8 (9): 1893-1896
Abstract
[structure: see text] The first member of a new class of five-membered B-ring analogs of bryostatin has been synthesized and tested for its ability to bind and translocate protein kinase C (PKC). This synthesis extends the utility of our previously introduced macrotransacetalization strategy to the formation of five-membered dioxolane B-ring analogs. This analog exhibits potent, single-digit nanomolar affinity to PKC and selectively translocates novel PKC isozymes.
View details for DOI 10.1021/ol060457z
View details for Web of Science ID 000237174500037
View details for PubMedID 16623578
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Rhodium(I)-catalyzed [4+2+2] cycloadditions of 1,3-dienes, alkenes, and alkynes for the synthesis of cyclooctadienes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2006; 128 (16): 5354-5355
Abstract
The first [4+2+2] cycloadditions involving terminal alkynes and diene-enes, including a fully intramolecular example, are reported resulting in the formation of cyclooctadienes using [RhCl(CO)2]2 (5 mol %) treated with AgSbF6 (10 mol %) as a precatalyst. The reaction is general for a variety of terminal alkynes, as well as variously substituted diene-enes (yields up to 88%).
View details for DOI 10.1021/ja060878b
View details for Web of Science ID 000237125100027
View details for PubMedID 16620102
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Total synthesis and biological evaluation of 11-desmethyllaulimalide, a highly potent simplified laulimalide analogue
ORGANIC LETTERS
2006; 8 (7): 1507-1510
Abstract
[reaction: see text] A step-economical synthesis of 11-desmethyllaulimalide (2) is reported. This simplified analogue is available through an improved second-generation synthetic approach to the laulimalides, in a shorter step count and from much less expensive starting material than the parent compound. This new lead retains the anticancer function of laulimalide.
View details for DOI 10.1021/o1060233g
View details for Web of Science ID 000236397000064
View details for PubMedID 16562928
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Correlation of F0F1-ATPase inhibition and antiproliferative activity of apoptolidin analogues
ORGANIC LETTERS
2006; 8 (4): 589-592
Abstract
[structure: see text] Apoptolidin (1) exhibits potent and highly selective apoptosis inducing activity against sensitive cancer cell lines and is hypothesized to act by inhibition of mitochondrial F(0)F(1)-ATP synthase. A series of apoptolidin derivatives, including a new intermolecular Diels-Alder adduct, were analyzed for antiproliferative activity in E1A-transformed rat fibroblasts. Potent F(0)F(1)-ATPase inhibition was not a sufficient determinant of antiproliferative activity for several analogues, suggesting the existence of a secondary biological target or more complex mode of action for apoptolidin.
View details for DOI 10.1021/ol052800q
View details for Web of Science ID 000235534800011
View details for PubMedID 16468718
View details for PubMedCentralID PMC2533578
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Rh-I-catalyzed C-C bond activation: Seven-membered ring synthesis by a [6+1] carbonylative ring-expansion reaction of allenylcyclobutanes
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2006; 45 (24): 3957-3960
View details for DOI 10.1002/anie.200600806
View details for Web of Science ID 000238501500013
View details for PubMedID 16683295
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Molecular understanding of cellular uptake by arginine-rich cell penetrating peptides
Symposium on Polymeric Drug Delivery held at the 226th National ACS Meeting
AMER CHEMICAL SOC. 2006: 166–181
View details for Web of Science ID 000236279500012
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Metal-catalyzed [2+2+1] cycloadditions of 1,3-dienes, allenes, and CO
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2006; 45 (15): 2459-2462
View details for DOI 10.1002/anie.200600300
View details for Web of Science ID 000236768600029
View details for PubMedID 16526073
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Actin is the primary cellular receptor of bistramide A
NATURE CHEMICAL BIOLOGY
2005; 1 (7): 383-388
Abstract
Bistramide A (1) is a marine natural product with broad, potent antiproliferative effects. Bistramide A has been reported to selectively activate protein kinase C (PKC) delta, leading to the view that PKCdelta is the principal mediator of antiproliferative activity of this natural product. Contrary to this observation, we established that bistramide A binds PKCdelta with low affinity, does not activate this kinase in vitro and does not translocate GFP-PKCdelta. Furthermore, we identified actin as the cellular receptor of bistramide A. We report that bistramide A disrupts the actin cytoskeleton, inhibits actin polymerization, depolymerizes filamentous F-actin in vitro and binds directly to monomeric G-actin in a 1:1 ratio with a Kd of 7 nM. We also constructed a fully synthetic9 bistramide A-based affinity matrix and isolated actin as a specific bistramide A-binding protein. This activity provides a molecular explanation for the potent antiproliferative effects of bistramide A, identifying it as a new biochemical tool for studies of the actin cytoskeleton and as a potential lead for development of a new class of antitumor agents.
View details for DOI 10.1038/nchembio748
View details for Web of Science ID 000233447700010
View details for PubMedID 16372404
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Dendrimeric molecular transporters: Synthesis and evaluation of tunable polyguanidino dendrimers that facilitate cellular uptake
ORGANIC LETTERS
2005; 7 (22): 4815-4818
Abstract
[reaction: see text] Nine fluorescently labeled structurally varied polyguanidino dendrimers based on diamino acid monomeric units were individually synthesized in an efficient, scalable sequence using a trifluoroacetamide protecting group-perguanidinylation strategy. While the dendrimers varied significantly in their ability to enter a human lymphocyte cell line, the best transporters out-performed an oligoarginine reference standard.
View details for DOI 10.1021/ol051496y
View details for Web of Science ID 000232817700008
View details for PubMedID 16235896
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Function oriented synthesis: The design, synthesis, and biological evaluation of a structurally and functionally unique class of therapeutic leads for cancer treatment
AMER CHEMICAL SOC. 2005: U2634-U2635
View details for Web of Science ID 000236797305217
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Apoptolidins B and C: Isolation, structure determination, and biological activity
ORGANIC LETTERS
2005; 7 (14): 3025-3028
Abstract
[reaction: see text] Apoptolidin (1) is a promising new therapeutic lead that exhibits remarkable selectivity against cancer cells relative to normal cells. We report the isolation, characterization, solution structure, stability, and biological activity of two new members of this family: apoptolidins B (2) and C (3). These new agents are found to have antiproliferative activity on par with or better than apoptolidin itself in an assay with H292 lung cancer cells.
View details for DOI 10.1021/ol051074o
View details for Web of Science ID 000230213100056
View details for PubMedID 15987196
View details for PubMedCentralID PMC2533581
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Rh(I)-catalyzed cleavage of unactivated C-O bonds - Carbonylative rearrangement reactions of allenyl ethers to 2-carboalkoxy-1,3-dienes
CANADIAN JOURNAL OF CHEMISTRY
2005; 83 (6-7): 838-842
View details for DOI 10.1139/V05-085
View details for Web of Science ID 000231832500041
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Role of the A-ring of bryostatin analogues in PKC binding: Synthesis and initial biological evaluation of new A-ring-modified bryologs
ORGANIC LETTERS
2005; 7 (10): 1995-1998
Abstract
The syntheses of three newly designed bryostatin analogues are reported. These simplified analogues, which lack the A-ring present in the natural product but possess differing groups at C9, were obtained using a divergent approach from a common intermediate. All three analogues exhibit potent, single-digit nanomolar affinity to protein kinase C.
View details for DOI 10.1021/ol0504650
View details for Web of Science ID 000228984500028
View details for PubMedID 15876038
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Transition metal-catalyzed intermolecular [5+2] and [5+2+1] cycloadditions of allenes and vinylcyclopropanes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2005; 127 (18): 6530-6531
Abstract
Initial examples of the intermolecular Rh(I)-catalyzed [5+2] cycloaddition reaction of bifunctional allenes and vinylcyclopropanes are described. The reactions proceed with facility and in yields of up to 99% with a variety of alkyne-, ester-, styrene-, or cyano-substituents on the allene to afford the corresponding cycloadducts. In the presence of CO, the reaction proceeds to an eight-membered ring cycloadduct and its transannularly closed product, providing the first example of a three-component [5+2+1] cycloaddition with allenes.
View details for DOI 10.1021/ja043671w
View details for Web of Science ID 000229055800015
View details for PubMedID 15869263
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Identification of a tunable site in bryostatin analogs: C20 bryologs through late stage diversification
ORGANIC LETTERS
2005; 7 (6): 1177-1180
Abstract
[structure: see text] The C20 region of our bryostatin analogs was identified as a nonpharmacophoric site that could be varied to tune analogs for function and physical properties without significantly affecting their binding affinity for PKC. The use of this site in a late-stage diversification strategy has enabled the facile synthesis of a variety of new C20 analogs, all of which retain nanomolar affinity for PKC, in agreement with our pharmacophore hypothesis.
View details for DOI 10.1021/ol0501931
View details for Web of Science ID 000227621000056
View details for PubMedID 15760168
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Multicomponent cycloadditions: The four-component [5+1+2+1] cycloaddition of vinylcyclopropanes, alkynes, and CO
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2005; 127 (9): 2836-2837
Abstract
Prompted by the view that intermediates of transition metal-catalyzed reactions could be intercepted by one or more additional components, studies in our laboratory have led to the design and development of new three-component [5+2+1], [4+2+1], and [2+2+1] cycloadditions. These continuing studies have now led to the identification of a fundamentally new four-component [5+1+2+1] cycloaddition reaction of vinylcyclopropanes, alkynes and CO, yielding hydroxyindanone products in generally good yields. Terminal alkynes bearing aryl or alkyl groups are tolerated well. Substitution at any position of the VCP leads predictably to substituted hydroxyindanone products. Using a bis-alkynyl substrate, the reaction can be carried out bi-directionally, forming 10 C-C bonds and four new rings from seven components in a single, operationally simple process.
View details for DOI 10.1021/ja042728b
View details for Web of Science ID 000227479600021
View details for PubMedID 15740103
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Adaptive translocation: the role of hydrogen bonding and membrane potential in the uptake of guanidinium-rich transporters into cells
ADVANCED DRUG DELIVERY REVIEWS
2005; 57 (4): 495-504
Abstract
A mechanistic hypothesis is presented for how water-soluble guanidinium-rich transporters attached to small cargoes (MW ca. <3000) can migrate across the non-polar lipid membrane of a cell and enter the cytosol. Positively charged and water-soluble, arginine oligomers can associate with negatively charged, bidentate hydrogen bond acceptor groups of endogenous membrane constituents, leading to the formation of membrane-soluble ion pair complexes. The resultant less polar, ion pair complexes partition into the lipid bilayer and migrate in a direction, and with a rate, influenced by the membrane potential. The complex dissociates on the inner leaf of the membrane and the transporter conjugate enters the cytosol. This mechanism could also be involved in the translocation of guanidinium-rich molecules that are endocytosed due to their size or the conditions of the assay, across the endosomal membrane.
View details for DOI 10.1016/j.addr.2004.10.003
View details for Web of Science ID 000227570500003
View details for PubMedID 15722160
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Late-stage intermolecular CH activation for lead diversification: A highly chemoselective oxyfunctionalization of the C-9 position of potent bryostatin analogues
ORGANIC LETTERS
2005; 7 (1): 79-82
Abstract
Treatment of highly potent and densely functionalized bryostatin analogue 1 with dimethyldioxirane afforded the C-9 hydroxylated hemiketal 2 via oxyfunctionalization of the C9-CH bond, one of 12 CH bonds geminal to an oxygen substituent in 1. When bryostatin analogue 3 was subjected to identical conditions, oxidation of a C-26 secondary hydroxyl group was found to compete with C-9 hydroxylation. Complete selectivity for C-9 hydroxylation was restored upon acylation of the C-26 secondary alcohol.
View details for DOI 10.1021/o1047859w
View details for Web of Science ID 000226072100020
View details for PubMedID 15624982
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Effect of serum and antioxidants on the immunogenicity of protein kinase C-activated chronic lymphocytic leukemia cells
JOURNAL OF IMMUNOTHERAPY
2005; 28 (1): 28-39
Abstract
Since the intrinsically poor immunogenicity of chronic lymphocytic leukemia (CLL) cells might be a key factor in allowing them to avoid immune control mechanisms, the development of methods to enhance CLL cell immunogenicity might lead to improved disease control. The ability of CLL cells to stimulate T cells was increased significantly by the protein kinase C (PKC) agonist phorbol myristic acetate (PMA). However, under serum-free conditions, PMA-activated CLL cells died within 48 hours. Antioxidants, such as 2-mercaptoethanol (2-ME), or fetal calf serum could prevent the death of these cells but caused them to enter distinct states of differentiation. In the presence of 2-ME, PMA-activated CLL cells extended dendritic-like protrusions and exhibited increased T-cell stimulatory capacity. In the presence of serum, PMA-activated CLL cells developed fewer dendrites, made less IL-10 and more IL-12 p40 mRNA transcripts, and showed an increased capacity to induce IFN-gamma production by T cells. The effects of serum on the promotion of type 1 immune responses by phorbol ester-activated CLL cells were dominant and correlated with activation of the NF-kappaB signaling pathway. Other PKC agonists, such as Bryostatin-1 and a synthetic Bryostatin analog (Picolog), had similar effects on CLL cells. The observation that CLL cells can acquire features of dendritic cells that promote type 1 immunity may find clinical application in immunotherapeutic strategies for this disease.
View details for Web of Science ID 000226087300004
View details for PubMedID 15614042
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Rhodium(I)-Catalyzed [5+2], [6+2], and [5+2+1] Cycloadditions: New Reactions for Organic Synthesis
MODERN RHODIUM-CATALYZED ORGANIC REACTIONS
2005: 263-299
View details for DOI 10.1002/3527604693.ch13
View details for Web of Science ID 000298408400015
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Synthetic bryostatin analogues activate the RasGRP1 signaling pathway
JOURNAL OF MEDICINAL CHEMISTRY
2004; 47 (26): 6638-6644
Abstract
The functional properties of four diacylglycerol (DAG) analogues were compared using cell-signaling assays based on the protein RasGRP1, a DAG-regulated Ras activator. Compounds 1 and 2, synthetic analogues of bryostatin 1, were compared to authentic bryostatin 1 and phorbol 12-myristate-13-acetate (PMA). The two "bryologues" were able to activate RasGRP1 signaling rapidly in cultured cells and isolated mouse thymocytes. They elicited expression of the T cell activation marker CD69 in human T cells. DAG analogues promptly recruited RasGRP1 to cell membranes, but they did not induce RasGRP1 proteolysis. Bryostatin 1 and compounds 1 and 2 appeared to be less potent than PMA at inducing aggregation of mouse thymocytes, a PKC-dependent, RasGRP1-independent response. In addition to sharing potential anticancer properties with bryostatin 1, compounds 1 and 2 might be clinically useful as modulators of the immune system.
View details for DOI 10.1021/jm0495069
View details for Web of Science ID 000225748500026
View details for PubMedID 15588099
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Simplified analogs of bryostatin with anticancer activity display greater potency for translocation of PKC delta-GFP
CHEMISTRY & BIOLOGY
2004; 11 (9): 1261-1267
Abstract
Structurally simplified analogs of bryostatin 1, a marine natural product in clinical trials for the treatment of cancer, have been shown to be up to 50 times more potent than bryostatin 1 at inducing the translocation of PKCdelta-GFP from the cytosol of rat basophilic leukemia (RBL) cells. The end distribution of the protein is similar for all three compounds, despite a significant difference in translocation kinetics. The potency of the compounds for inducing the translocation response appears to be only qualitatively related to their binding affinity for PKC, highlighting the importance of using binding affinity in conjunction with real-time measurements of protein localization for the pharmacological profiling of biologically active agents.
View details for DOI 10.1016/j.chembiol.2004.06.014
View details for Web of Science ID 000224228900009
View details for PubMedID 15380186
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Guanidinium-rich molecular transporters: Mechanisms and applications.
AMER CHEMICAL SOC. 2004: U910
View details for Web of Science ID 000223712803855
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Role of membrane potential and hydrogen bonding in the mechanism of translocation of guanidinium-rich peptides into cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2004; 126 (31): 9506-9507
Abstract
The results described herein support a mechanistic hypothesis for how guanidine-rich transporters attached to small cargos (MW ca. <3000) can migrate across the lipid membrane of a cell and directly enter the cytosol. Arginine oligomers are found to partition almost completely into the aqueous layer of a water-octanol bilayer. However, when the same partitioning experiment is conducted in the presence of sodium laurate, a representative negatively charged membrane constituent, the arginine oligomer partitions almost completely (>95%) into the octanol layer. In contrast, ornithine oligomers partition almost exclusively into the water layer with and without added sodium laurate. The different partitioning between guanidinium-rich and ammonium-rich oligomers in the presence of sodium laurate is consistent with the ability of the former to form a bidentate hydrogen bonded ion pair. Mono- and dimethylated arginine oligomers, which like ornithine can only efficiently form monodentate hydrogen bonds, were prepared and found to exhibit poor cellular uptake. Ion pair formation converts a once water-soluble agent to a lipid-soluble agent, thereby reducing the energetic penalty for passage of guanidine-rich transporters through the lipid bilayer. Uptake of guanidine-rich transporters is known to be an energy-dependent process, and this requirement for cellular ATP is now rationalized by the inhibition of guanidine-rich transporter uptake in the presence of agents that reduce the membrane potential. Specifically, incubation of cells in buffers with high potassium ion concentrations or pretreatment of cells with gramicidin A reduces the cellular uptake of Fl-aca-arg8-CONH2 by >90%. Furthermore, the reciprocal experiment of hyperpolarizing the cell with valinomycin increased uptake by >1.5 times. In summary, we propose that the water-soluble, positively charged guanidinium headgroups of the transporter form bidentate hydrogen bonds with H-bond acceptor functionality on the cell surface. The resultant ion pair complexes partition into the lipid bilayer and migrate across at a rate related to the membrane potential. The complex dissociates on the inner leaf of the membrane, and the transporter enters the cytosol. This hypothesis does not preclude uptake by other mechanisms, including endocytosis, which is likely to dominate with large cargos.
View details for DOI 10.1021/ja0482536
View details for Web of Science ID 000223110100020
View details for PubMedID 15291531
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On the mechanism of [Rh(CO)(2)Cl](2)-catalyzed intermolecular (5+2) reactions between vinylcyclopropanes and alkynes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2004; 126 (30): 9154-9155
Abstract
DFT calculations have been applied to investigate the reaction mechanism of rhodium dimer, [Rh(CO)2Cl]2, catalyzed intermolecular (5 + 2) reactions between vinylcyclopropanes and alkynes. The catalytic species is Rh(CO)Cl and the catalytic cycle is through the sequential reactions of cyclopropyl cleavage of vinylcyclopropane, alkyne insertion (rate-determining step), and a migratory reductive elimination.
View details for DOI 10.1021/ja048739m
View details for Web of Science ID 000222950900003
View details for PubMedID 15281784
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Nanotube molecular transporters: Internalization of carbon nanotube-protein conjugates into mammalian cells
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2004; 126 (22): 6850-6851
Abstract
The interactions between various functionalized carbon nanotubes and several types of human cancer cells are explored. We have prepared modified nanotubes and have shown that these can be derivatized in a way that enables attachment of small molecules and of proteins, the latter through a novel noncovalent association. The functionalized carbon nanotubes enter nonadherent human cancer cells as well as adherent cell lines (CHO and 3T3) and by themselves are not toxic. While the fluoresceinated protein streptavidin (MW approximately 60 kD) by itself does not enter cells, it readily enters cells when complexed to a nanotube-biotin transporter and exhibits dose-dependent cytotoxicity. The uptake pathway is consistent with adsorption-mediated endocytosis. The use of carbon nanotubes as molecular transporters could be exploited for various cargos. The biocompatibility and unique physical, electrical, optical, and mechanical properties of nanotubes provide the basis for new classes of materials for drug, protein, and gene delivery applications.
View details for DOI 10.1021/ja0486059
View details for Web of Science ID 000221828200007
View details for PubMedID 15174838
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Microtubule-stabilizing agents based on designed laulimalide analogues
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2004; 101 (23): 8803-8808
Abstract
Laulimalide is a potent, structurally unique microtubule-stabilizing agent originally isolated from the marine sponge Cacospongia mycofijiensis. Laulimalide exhibits an activity profile different from other microtubule-binding agents, notably including effectiveness against paclitaxel-resistant cells, but it is intrinsically unstable. Five analogues of laulimalide were designed to exhibit enhanced chemical stability yet retain its exceptional biological activities. Evaluations of these analogues showed that all are effective inhibitors of cancer-cell proliferation yet differ substantially in potency with an IC(50) range of 0.12-16.5 microM. Although all of the analogues initiated cellular changes similar to laulimalide, including increased density of interphase microtubules, aberrant mitotic spindles, and ultimately apoptosis, differences among the analogues were apparent. The two most potent analogues, C(16)-C(17)-des-epoxy laulimalide and C(20)-methoxy laulimalide, appear to have a mechanism of action identical to laulimalide. The C(16)-C(17)-des-epoxy, C(20)-methoxy laulimalide derivative, which incorporates both chemical changes of the most potent analogues, was significantly less potent and initiated the formation of unique interphase microtubules unlike the parent compound and other analogues. Two C(2)-C(3)-alkynoate derivatives had lower potency, and they initiated abnormal microtubule structures but did not cause micronucleation or extensive G(2)/M accumulation. Significantly, paclitaxel- and epothilone-resistant cell lines were less resistant to the laulimalide analogues. In summary, analogues of laulimalide designed to minimize or eliminate its intrinsic instability have been synthesized, and some have been found to retain the unique biological activities of laulimalide.
View details for Web of Science ID 000222037000056
View details for PubMedID 15161976
View details for PubMedCentralID PMC423276
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Rhodium(I)-Catalyzed [2+2+1] cycloadditions of 1,3-dienes, alkenes, and CO
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2004; 126 (19): 5948-5949
Abstract
Initial examples of a Rh(I)-catalyzed [2+2+1] reaction of diene-enes and CO are described. This method allows for the facile, efficient, and diastereoselective construction of a variety of alkenyl cyclopentanones in good to excellent yields. Control studies show that the diene moiety is required for this process as bis-enes do not give the [2+2+1] products under the same conditions.
View details for Web of Science ID 000221416700010
View details for PubMedID 15137743
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Selectivity in translocation of protein kinase C isoforms by new analogs of bryostatin.
AMER CHEMICAL SOC. 2004: U70
View details for Web of Science ID 000223655700343
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Function oriented synthesis: the design, synthesis, PKC binding and translocation activity of a new bryostatin analog.
Current drug discovery technologies
2004; 1 (1): 1-11
Abstract
Bryostatin 1 represents a novel and potent therapeutic lead with a unique activity profile. Its natural and synthetic availability is severely limited. Function oriented synthesis provides a means to address this supply problem through the design of synthetically more accessible simplified structures that at the same time incorporate improved functional activity. Pharmacophore searching and a new computer aided visualization of a possible binding mode are combined with an understanding of function and knowledge of synthesis to design and prepare a new and simplified compound with bryostatin-like function in biological systems. This new compound is a potent ligand for protein kinase C in vitro (K(i) = 8.0 nM). More significantly, the described molecule retains the functional ability to translocate a PKCdelta-GFP fusion protein in RBL cells. The extent of protein translocation and the sub-cellular localization induced by this new compound is similar to that seen in response to bryostatin 1, indicating that the new molecule retains the functional activity of the natural product but is simpler and can be synthesized in a practical fashion.
View details for PubMedID 16472215
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Intermolecular dienyl Pauson-Khand reaction
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2004; 43 (23): 3076-3079
View details for DOI 10.1002/anie.200454117
View details for Web of Science ID 000222067400021
View details for PubMedID 15188486
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A new synthetic approach to the C ring of known as well as novel bryostatin analogues
ORGANIC LETTERS
2003; 5 (24): 4549-4552
Abstract
[reaction: see text] A new approach to the synthesis of the C ring subunit of known and potential bryostatin analogues is described. The convergent approach, illustrated above, requires fewer steps and offers greater flexibility in rapidly accessing diverse C ring analogues.
View details for DOI 10.1021/ol0355332
View details for Web of Science ID 000186728600005
View details for PubMedID 14627380
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Delivery of antimicrobials into parasites
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2003; 100 (24): 14281-14286
Abstract
To eliminate apicomplexan parasites, inhibitory compounds must cross host cell, parasitophorous vacuole, and parasite membranes and cyst walls, making delivery challenging. Here, we show that short oligomers of arginine enter Toxoplasma gondii tachyzoites and encysted bradyzoites. Triclosan, which inhibits enoyl-ACP reductase (ENR), conjugated to arginine oligomers enters extracellular tachyzoites, host cells, tachyzoites inside parasitophorous vacuoles within host cells, extracellular bradyzoites, and bradyzoites within cysts. We identify, clone, and sequence T. gondii enr and produce and characterize enzymatically active, recombinant ENR. This enzyme has the requisite amino acids to bind triclosan. Triclosan released after conjugation to octaarginine via a readily hydrolyzable ester linkage inhibits ENR activity, tachyzoites in vitro, and tachyzoites in mice. Delivery of an inhibitor to a microorganism via conjugation to octaarginine provides an approach to transporting antimicrobials and other small molecules to sequestered parasites, a model system to characterize transport across multiple membrane barriers and structures, a widely applicable paradigm for treatment of active and encysted apicomplexan and other infections, and a generic proof of principle for a mechanism of medicine delivery.
View details for DOI 10.1073/pnas.2436169100
View details for Web of Science ID 000186803800095
View details for PubMedID 14623959
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Breaching biological barriers: protein translocation domains as tools for molecular imaging and therapy.
Molecular imaging
2003; 2 (4): 313-323
Abstract
The lipid bilayer of a cell presents a significant barrier for the delivery of many molecular imaging reagents into cells at target sites in the body. Protein translocation domains (PTDs) are peptides that breach this barrier. Conjugation of PTDs to imaging agents can be utilized to facilitate the delivery of these agents through the cell wall, and in some cases, into the cell nucleus, and have potential for in vitro and in vivo applications. PTD imaging conjugates have included small molecules, peptides, proteins, DNA, metal chelates, and magnetic nanoparticles. The full potential of the use of PTDs in novel in vivo molecular probes is currently under investigation. Cells have been labeled in culture using magnetic nanoparticles derivatized with a PTD and monitored in vivo to assess trafficking patterns relative to cells expressing a target antigen. In vivo imaging of PTD-mediated gene transfer to cells of the skin has been demonstrated in living animals. Here we review several natural and synthetic PTDs that have evolved in the quest for easier translocation across biological barriers and the application of these peptide domains to in vivo delivery of imaging agents.
View details for PubMedID 14717330
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Synthesis and biological evaluation of (-)-laulimalide analogues
ORGANIC LETTERS
2003; 5 (19): 3507-3509
Abstract
[reaction: see text] The syntheses of five laulimalide analogues are described, incorporating modifications at the C(16)-C(17)-epoxide, the C(20)-alcohol, as well as the C(1)-C(3)-enoate of the parent natural product. The resultant analogues are active in drug-sensitive HeLa and MDA-MB-435 cell lines. Significantly, like laulimalide, these analogues are poor substrates for the drug transport protein P-glycoprotein (Pgp) and are thus effective against Taxol-resistant cell lines.
View details for DOI 10.1021/ol035339f
View details for Web of Science ID 000185329300036
View details for PubMedID 12967311
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Arginine-based molecular transporters: The synthesis and chemical evaluation of releasable taxol-transporter conjugates
ORGANIC LETTERS
2003; 5 (19): 3459-3462
Abstract
[structure: see text] A flexible and efficient procedure has been developed for the conjugation of taxol to various arginine-based molecular transporters via the taxol C2' O-chloroacetyl derivative. The resultant taxol-transporter conjugates are highly water soluble and release free taxol with half-lives of minutes to hours depending on the pH and the linker structure.
View details for DOI 10.1021/ol035234c
View details for Web of Science ID 000185329300024
View details for PubMedID 12967299
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Gene transfer via reversible plasmid condensation with cysteine-flanked, internally spaced arginine-rich peptides
HUMAN GENE THERAPY
2003; 14 (13): 1225-1233
Abstract
Nonviral gene transfer offers biosafety, stability, and expense advantages over viruses; however, it has suffered from poor efficiency. Because arginine-rich peptides facilitate uptake of macromolecules such as proteins, liposomes, and iron nanoparticles, we explored their potential in enhancing plasmid DNA delivery. In their unmodified form, known protein transduction sequences, including hepta-arginine and Tat(47-57), failed to support effective gene delivery. However, by flanking a core of consecutive arginines with amino- and carboxy-terminal cysteines in vitro gene transfer was observed. Furthermore, interspersing arginines with glycine and histidine residues achieved reversible plasmid condensation and dramatically increased transfection levels in a variety of cell types. Unlike most available cationic homopolymers that function only in vitro, these new peptides also increased gene expression in both murine and human tissue in vivo. Thus, cysteine-flanked, internally spaced arginine-rich (CFIS-R) peptides represent a new approach to efficient nonviral plasmid delivery using rationally designed protein transduction domains.
View details for Web of Science ID 000184794500002
View details for PubMedID 12952594
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Facile synthetic access to and biological evaluation of the macrocyclic core of apoptolidin
ORGANIC LETTERS
2003; 5 (13): 2299-2302
Abstract
Oxidative cleavage of the C-20/C-21 bond in apoptolidin (1) provides two fragments of similar complexity, facilitating a divide-and-diversify strategy for the determination of the structural basis for apoptolidin's biological activity, the remarkably selective induction of apoptosis in sensitive cell lines. The ability of compounds derived from this cleavage to inhibit mitochondrial F(0)F(1)-ATPase is reported. [structure: see text]
View details for DOI 10.1021/ol0346335
View details for Web of Science ID 000183692600027
View details for PubMedID 12816433
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Photoinduced cleavage of DNA by bromofluoroacetophenone-pyrrolecarboxamide conjugates
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
2003; 13 (10): 1763-1766
Abstract
Bromofluoroacetophenone derivatives which produce fluorine substituted phenyl radicals that cleave DNA upon excitation were investigated as a novel photonuclease. Pyrrolecarboxamide-conjugated bromofluoroacetophenones; 4'-bromo-2'-fluoroacetophenone and 2'-bromo-4'-fluoroacetophenone were synthesized and their DNA cleaving activities and sequence selectivities were determined. Bromofluoroacetophenone-pyrrolecarboxamide conjugates were found to be effective DNA cleaving agents upon irradiation in concentration dependent manner based on plasma relaxation assay. The DNA cleaving activities of 2'-bromo-4'-fluoroacetophenone derivatives were larger than those of 4'-bromo-2'-fluoroacetophenone derivatives.
View details for DOI 10.1016/S0960-894X(03)00212-9
View details for Web of Science ID 000182913600034
View details for PubMedID 12729660
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Guanidinium rich peptide transporters and drug delivery
CURRENT PROTEIN & PEPTIDE SCIENCE
2003; 4 (2): 105-124
Abstract
The use of peptide or peptidomimetic transporters to enable or enhance the uptake of drugs or probe molecules into cells and tissues has received increasing research attention and clinical interest over the past 10 years. This review summarizes a class of transporters that have been studied and focuses on the variation and use of guanidinium based transporters to facilitate the uptake of various types of molecules into cells and tissues. Lead conjugates in this area are currently in clinical trials.
View details for Web of Science ID 000181704200004
View details for PubMedID 12678850
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Toward a structure-activity relationship for apoptolidin: Selective functionalization of the hydroxyl group array
ORGANIC LETTERS
2003; 5 (4): 487-490
Abstract
[reaction: see text] To investigate the structural basis for the exceptional selectivity and activity of apoptolidin (1), a strategy has been devised that allows for selective functionalization of seven of its eight hydroxyl groups based on progressive silyl protection, derivatization, and deprotection. The syntheses of these derivatives and their ability to inhibit F(0)F(1)-ATPase are reported.
View details for DOI 10.1021/ol027366w
View details for Web of Science ID 000181077200027
View details for PubMedID 12583750
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A concise, selective synthesis of the polyketide spacer domain of a potent bryostatin analogue
ORGANIC LETTERS
2003; 5 (3): 277-279
Abstract
[reaction: see text] A concise, asymmetric synthesis of the polyketide spacer domain portion (C1-C13) of a highly potent bryostatin analogue was developed. The route utilizes asymmetric hydrogenation methodology to install the C3, C5, and C11 stereocenters, while a substrate directed syn reduction sets the C9 stereocenter. The spacer domain 1 is obtained in 10 steps with a 25% overall yield and is readily incorporated into the synthesis of 2.
View details for DOI 10.1021/ol0272390
View details for Web of Science ID 000180766400012
View details for PubMedID 12556171
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Inspirations from nature. New reactions, therapeutic leads, and drug delivery systems
PURE AND APPLIED CHEMISTRY
2003; 75 (2-3): 143-155
View details for Web of Science ID 000182416500002
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The dienyl Pauson-Khand reaction
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2003; 42 (16): 1853-1857
View details for Web of Science ID 000182751700018
View details for PubMedID 12722081
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Rhodium-catalyzed [5+2] cycloaddition reactions in water
SYNLETT
2003: 1295-1298
View details for Web of Science ID 000184219100017
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Transition metal-catalyzed hetero-[5+2] cycloadditions of cyclopropyl imines and alkynes: Dihydroazepines from simple, readily available starting materials
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2002; 124 (51): 15154-15155
Abstract
The first example of a transition metal-catalyzed hetero-[5 + 2] cycloaddition reaction is described. Use of cyclopropyl imines as five-atom components, an alkyne as a two-carbon component, and a Rh(I) catalyst enables a new route to dihydroazepines. This new hetero-[5 + 2] cycloaddition works well with aldimines, ketimines, and with substituted cyclopropanes and affords the desired dihydroazepines in excellent yields as single regioisomers. Use of serial imine formation/aza-[5 + 2] cycloaddition generates the desired dihydroazepines in one operation from three commercially available starting materials. The reaction has been scaled to give gram quantities of dihydroazepine.
View details for DOI 10.1021/ja0285013
View details for Web of Science ID 000180006600005
View details for PubMedID 12487573
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The practical synthesis of a novel and highly potent analogue of bryostatin
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2002; 124 (46): 13648-13649
Abstract
Macrocycle 1 is a new highly potent analogue of bryostatin 1, a promising anti-cancer agent currently in human clinical trials. In vitro, 1 displays picomolar affinity for PKC and exhibits over 100-fold greater potency than bryostatin 1 when tested against various human cancer cell lines. Macrocycle 1 can be generated in clinically required amounts by chemical synthesis in only 19 steps (LLS) and represents a new clinical lead for the treatment of cancer.
View details for DOI 10.1021/ja027509+
View details for Web of Science ID 000179269800004
View details for PubMedID 12431074
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Oligocarbamate molecular transporters: Design, synthesis, and biological evaluation of a new class of transporters for drug delivery
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2002; 124 (45): 13382-13383
Abstract
Molecular transporters have the ability to deliver drugs and probe molecules into cells and tissues irrespective of their physical properties. We now report the design, synthesis, and biological evaluation of a new family of molecular transporters, guanidinylated oligocarbamates that enable exceptionally efficient uptake into cells and tissues. The synthesis features a solid-phase stepwise oligomerization to obtain the oligocarbamates and a single step perguanidinylation for the facile introduction of up to nine guanidinium groups. The oligocarbamate 9-mer is found to be among the most efficient transporters known, entering cells faster than even d-Arg9 and HIV-1 Tat49-57. Significantly, this new family of transporters also enables uptake into the formidable skin barrier of a probe molecule that by itself does not penetrate skin.
View details for DOI 10.1021/ja0275109
View details for Web of Science ID 000179122900022
View details for PubMedID 12418880
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Isoapoptolidin: Structure and activity of the ring-expanded isomer of apoptolidin
ORGANIC LETTERS
2002; 4 (22): 3819-3822
Abstract
[formula: see text] Apoptolidin (1) is a novel oncolytic lead that induces apoptosis in transformed cell lines with exceptional selectivity. We report the isolation and characterization of a ring-expanded macrolide isomer of apoptolidin: isoapoptolidin (2). The solution conformation of isoapoptolidin is described. The rate of isomerization was measured under biologically relevant conditions and found to approach equilibrium within the time frame of most cell-based assays. Isoapoptolidin's ability to inhibit mitochondrial F0F1-ATPase is over 10-fold less than that of apoptolidin.
View details for DOI 10.1021/o10266222
View details for Web of Science ID 000178877500012
View details for PubMedID 12599467
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Arginine-rich molecular transporters for drug delivery: Role of backbone spacing in cellular uptake
JOURNAL OF MEDICINAL CHEMISTRY
2002; 45 (17): 3612-3618
Abstract
Short oligomers of arginine, either alone or when conjugated to therapeutic agents or large biopolymers, have been shown to cross readily a variety of biological barriers (e.g., lipid bilayers and epithelial tissue). Molecular modeling suggests that only a subset of the side chain guanidinium groups of these transporters might be required for transport involving contact with a common surface such as a plasma membrane or cell surface receptor. To evaluate this hypothesis, a series of decamers were prepared that incorporated seven arginines and three nonarginine residues. Several of these mixed decamers were comparable to the all arginine decamer in their ability to enter cells. More significantly, these decamers containing seven arginines performed almost without exception better than heptaarginine itself, suggesting that spacing between residues is also important for transport. The influence of spacing was more fully evaluated with a library of oligomers incorporating seven arginines separated by one or more nonconsecutive, non-alpha-amino acids. This study led to the identification of a new series of highly efficient molecular transporters.
View details for DOI 10.1021/jm0105676
View details for Web of Science ID 000177346400008
View details for PubMedID 12166934
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Peptide delivery to tissues via reversibly linked protein transduction sequences
BIOTECHNIQUES
2002; 33 (1): 190-?
Abstract
The development of peptide-based therapeutics has suffered from challenges associated with delivery to intact tissue. In skin, an array of protein targets resides only tens of micrometers below the surface; however, because of difficulties in traversing the cutaneous barrier, the potentialfor peptide-based therapeutics remains unrealized. We have developed a general approach for topical peptide delivery into skin using releasable protein transduction sequences to enable peptide transport across tissue boundaries. Upon entry into the cell, the disulfide linkage between the peptide transduction sequences and peptide cargo is cleaved, permitting the dissociation of the highly charged peptide transduction sequences from the active peptide. A protype cargo peptide, the hemagglutinin (HA) epitope, was conjugated to a hepta-arginine protein transduction sequence via a releasable disulfide linkage. This construct penetrated the skin to deep dermis within 1 h after topical application. Consistent with the dissociation of the protein transduction and cargo sequences, absorbed protein transduction sequences and HA peptides displayed differential intracellular localization. Reversible protein transduction sequence linkage thus represents a noninvasive platform for tissue delivery of intact peptides with no requirement for viral vectors or parenteral injection and may be of broad utility in molecular therapy.
View details for PubMedID 12139245
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Total synthesis of (-)-laulimalide
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2002; 124 (18): 4956-4957
Abstract
(-)-Laulimalide (1), a structurally novel macrolide isolated in trace amounts from marine sponges, promotes abnormal tubulin polymerization and apoptosis in vitro, with a similar mode of action to that of Taxol(R), but with potentially less susceptibility to multidrug resistance. Herein, a flexible and convergent asymmetric synthesis of (-)-laulimalide is described. This synthesis featured a highly diastereoselective Sakurai reaction of 2 with 3 and a regioselective macrolactonization of an unprotected vicinal diol. Laulimalide was synthesized in 25 steps (longest linear; 36 overall) in 3.5% overall yield, providing a uniquely short and efficient route to 1 and its analogues.
View details for DOI 10.1021/ja0258428
View details for Web of Science ID 000175369100012
View details for PubMedID 11982349
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Three-component cycloadditions: The first transition metal-catalyzed [5+2+1] cycloaddition reactions
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2002; 124 (12): 2876-2877
Abstract
Prompted by our studies of transition metal-catalyzed [4+4], [4+2], [5+2], and [6+2] cycloadditions and by the view that these two-component reactions could be intercepted by a third component of one or more atoms, a new three-component transition metal-catalyzed cycloaddition is described. This new [5+2+1] cycloaddition proceeds in good to excellent yield and with high or complete regioselectivity with a variety of carbonyl-substituted alkynes to give bicyclo[3.3.0]octenone adducts, resulting from transannular closure of the intermediate eight-membered-ring cycloadduct. Effects of concentration, temperature, pressure, and catalyst loading on the efficiency of the reaction are discussed. This process provides access to complex building blocks for synthesis based on simple, readily available components.
View details for DOI 10.1021/ja0176301
View details for Web of Science ID 000174520500012
View details for PubMedID 11902870
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[(arene)Rh(cod)](+) complexes as catalysts for [5+2] cycloaddition reactions
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2002; 41 (23): 4550-?
View details for Web of Science ID 000179752500035
View details for PubMedID 12458535
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Molecular transporters for peptides: delivery of a cardioprotective epsilon PKC agonist peptide into cells and intact ischemic heart using a transport system, R-7
CHEMISTRY & BIOLOGY
2001; 8 (12): 1123-1129
Abstract
Recently, we reported a novel oligoguanidine transporter system, polyarginine (R(7)), which, when conjugated to spectroscopic probes (e.g., fluorescein) and drugs (e.g., cyclosporin A), results in highly water-soluble conjugates that rapidly enter cells and tissues. We report herein the preparation of the first R(7) peptide conjugates and a study of their cellular and organ uptake and functional activity. The octapeptide (psi)(epsilon)RACK was selected for this study as it is known to exhibit selective epsilon protein kinase C isozyme agonist activity and to reduce ischemia-induced damage in cardiomyocytes. However, (psi)(epsilon)RACK is not cell-permeable.Here we show that an R(7)-(psi)(epsilon)RACK conjugate readily enters cardiomyocytes, significantly outperforming (psi)(epsilon)RACK conjugates of the transporters derived from HIV Tat and from Antennapedia. Moreover, R(7)-(psi)(epsilon)RACK conjugate reduced ischemic damage when delivered into intact hearts either prior to or after the ischemic insult.Our data suggest that R(7) converts a peptide lead into a potential therapeutic agent for the ischemic heart.
View details for PubMedID 11755391
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An efficient, scalable synthesis of the molecular transporter octaarginine via a segment doubling strategy
ORGANIC LETTERS
2001; 3 (21): 3229-3232
Abstract
[reaction: see text]. Short oligomers of arginine function as remarkably efficient molecular transporters of drugs and probe molecules into cells and tissue. Currently, these compounds are prepared on resin through a unidirectional solid-phase synthesis. To extend the utility of these compounds for therapeutic and research applications, a scalable solution-phase synthesis of Arg8 (1) has been developed on the basis of a segment doubling strategy that proceeds in 13 steps and 28% overall yield from 4, including a novel one-step perdeprotection-perguanidinylation reaction.
View details for DOI 10.1021/ol0161108
View details for Web of Science ID 000171708000001
View details for PubMedID 11594801
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Serial [5+2]/[4+2] Cycloadditions: Facile, Preparative, Multi-Component Syntheses of Polycyclic Compounds from Simple, Readily Available Starting Materials This research was supported by grant CHE-9800445 from the National Science Foundation. The Stanford Graduate Fellowship (M.J.C.S. and G.G.G.) is gratefully acknowledged.
Angewandte Chemie (International ed. in English)
2001; 40 (20): 3895-3897
View details for PubMedID 11668567
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Serial [5+2]/[4+2] Cycloadditions: Facile, Preparative, Multi-Component Syntheses of Polycyclic Compounds from Simple, Readily Available Starting Materials.
Angewandte Chemie (International ed. in English)
2001; 40 (20): 3895-3897
Abstract
Four new bonds and up to four new stereocenters are formed in the title reactions which allow the conversion of readily available starting materials into complex bicyclo[5.4.0]undecane derivatives. The reactions are performed in a single, simple operation that can be conducted on a preparative scale (100 mmol thus far).
View details for DOI 10.1002/1521-3773(20011015)40:20<3895::AID-ANIE3895>3.0.CO;2-#
View details for PubMedID 29712128
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Toward the identification of selective modulators of protein kinase C (PKC) isozymes: Establishment of a binding assay for PKC isozymes using synthetic C1 peptide receptors and identification of the critical residues involved in the phorbol ester binding
BIOORGANIC & MEDICINAL CHEMISTRY
2001; 9 (8): 2073-2081
Abstract
Conventional and novel protein kinase C (PKC) isozymes contain two cysteine-rich C1 domains (C1A and C1B), both of which are candidate phorbol-12,13-dibutyrate (PDBu) binding sites. We previously synthesized C1 peptides (of approximately 50 residues) corresponding to all PKC isozymes and measured their PDBu binding affinity. While many of these peptide receptors exhibited PDBu affinities comparable to the respective complete isozyme, some of the C1A peptides could not be used because they undergo temperature dependent inactivation. This problem was however eliminated by 4 degrees C incubation or elongation of the 50-mer C1 peptides at both N- and C-termini to increase their folding efficiency and stability. These findings enabled us to determine the K(d)'s of PDBu for all PKC C1 peptides (except for theta-C1A) and establish the value of these peptides as readily available, stable, and easily handled surrogates of the individual isozymes. The resultant C1 peptide receptor library can be used to screen for new ligands with PKC isozyme and importantly C1 domain selectivity. Most of the C1 peptide receptors showed strong PDBu binding affinities with K(d)'s in the nanomolar range (0.45-7.4 nM). Two peptides (delta-C1A and theta-C1A) bound PDBu over 100-fold less tightly. To identify the residues that contribute to this affinity difference, several mutants of delta-C1A and theta-C1A were synthesized. Both the G9K mutant of delta-C1A and the P9K mutant of theta-C1A showed K(d)'s of 2-3 nM. This approach provides a useful procedure to determine the role of each C1 domain of the PKC isozymes by point mutation.
View details for Web of Science ID 000170138400014
View details for PubMedID 11504643
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Asymmetric synthesis of the tricyclic core of NGF-inducing cyathane diterpenes via a transition-metal-catalyzed [5+2] cycloaddition
ORGANIC LETTERS
2001; 3 (13): 2105-2108
Abstract
[reaction: see text] A concise asymmetric synthesis of the tricyclic core of cyathane diterpenes is described, based on a novel transition-metal-catalyzed intramolecular [5 + 2] cycloaddition of ynone-vinylcyclopropane 10 (assembled from commercially available (S)-(-)-limonene), which proceeds in 90% yield with >95% selectivity. This strategy provides efficient access (14 steps and 13% overall yield) to potential analogues as well as precursors of nerve growth factor (NGF)-inducing diterpenes.
View details for DOI 10.1021/ol0160699
View details for Web of Science ID 000169487700036
View details for PubMedID 11418060
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The C4 hydroxyl group of phorbol esters is not necessary for protein kinase C binding
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
2001; 11 (5): 719-722
Abstract
To investigate the role of the hydroxyl group at position 4 of the phorbol esters in protein kinase C (PKC) binding and function, 4beta-deoxy-phorbol-12,13-dibutyrate (4beta-deoxy-PDBu, 5a) and 4beta-deoxy-phorbol-13-acetate (6a) were synthesized from phorbol (1). The binding affinities of these 4beta-deoxy compounds (5a, 6a) to the 13 PKC isozyme C1 domains were quite similar to those of the corresponding 4beta-hydroxy compounds (4a, 4b), suggesting that the C4 hydroxyl group of phorbol esters is not necessary for PKC binding. Moreover, functional assays showed that 4beta-deoxy-PDBu (5a) exhibited biological activities (Epstein-Barr virus induction and superoxide generation) equally potent to those of PDBu (4a). These solution phase results differ from expectations based on the previously reported solid-phase structure of the complex of PKCdelta-C1B and phorbol-13-acetate (4b).
View details for Web of Science ID 000167375700025
View details for PubMedID 11266177
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Photocleavage of DNA by 4 '-bromoacetophenone analogs
ARCHIVES OF PHARMACAL RESEARCH
2001; 24 (1): 39-43
Abstract
4'-Bromoacetophenone analogs, which are able to generate monophenyl radicals capable of hydrogen atom abstraction, were investigated as possible photoinducible DNA cleaving agents. The potential of 4'-bromoacetophenone as a possible new DNA cleaver is explored. Pyrrolecarboxatmid conjugated 4'-bromoacetophenones, in particular, DNA cleaving activity and sequence-selectivity on the contiguous AT base pair sites.
View details for Web of Science ID 000167157200006
View details for PubMedID 11235810
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The first intermolecular transition metal-catalyzed [5+2] cycloadditions with simple, unactivated, vinylcyclopropanes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2001; 123 (1): 179-180
View details for Web of Science ID 000166258800024
View details for PubMedID 11273617
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Serial [5+2]/[4+2] cycloadditions: Facile, preparative, multi-component syntheses of polycyclic compounds from simple, readily available starting materials
ANGEWANDTE CHEMIE-INTERNATIONAL EDITION
2001; 40 (20): 3895-?
Abstract
Four new bonds and up to four new stereocenters are formed in the title reactions which allow the conversion of readily available starting materials into complex bicyclo[5.4.0]undecane derivatives. The reactions are performed in a single, simple operation that can be conducted on a preparative scale (100 mmol thus far).
View details for Web of Science ID 000171698000036
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Design and synthesis of new DNA photocleavers, 4 '-bromoacetophenone-pyrrolecarboxamide hybrid compounds
ARCHIVES OF PHARMACAL RESEARCH
2000; 23 (6): 585-588
Abstract
4-Bromoacetophenone-pyrrolecarboxamide conjugates were designed and synthesized as photoinducible DNA cleaving agents which can generate monophenyl radicals capable of causing the hydrogen atom abstraction which initiates the scission of DNA.
View details for Web of Science ID 000166072700009
View details for PubMedID 11156179
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The design, synthesis, and evaluation of molecules that enable or enhance cellular uptake: Peptoid molecular transporters
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
2000; 97 (24): 13003-13008
Abstract
Certain proteins contain subunits that enable their active translocation across the plasma membrane into cells. In the specific case of HIV-1, this subunit is the basic domain Tat(49-57) (RKKRRQRRR). To establish the optimal structural requirements for this translocation process, and thereby to develop improved molecular transporters that could deliver agents into cells, a series of analogues of Tat(49-57) were prepared and their cellular uptake into Jurkat cells was determined by flow cytometry. All truncated and alanine-substituted analogues exhibited diminished cellular uptake, suggesting that the cationic residues of Tat(49-57) play a principal role in its uptake. Charge alone, however, is insufficient for transport as oligomers of several cationic amino acids (histidine, lysine, and ornithine) are less effective than Tat(49-57) in cellular uptake. In contrast, a 9-mer of l-arginine (R9) was 20-fold more efficient than Tat(49-57) at cellular uptake as determined by Michaelis-Menton kinetic analysis. The d-arginine oligomer (r9) exhibited an even greater uptake rate enhancement (>100-fold). Collectively, these studies suggest that the guanidinium groups of Tat(49-57) play a greater role in facilitating cellular uptake than either charge or backbone structure. Based on this analysis, we designed and synthesized a class of polyguanidine peptoid derivatives. Remarkably, the subset of peptoid analogues containing a six-methylene spacer between the guanidine head group and backbone (N-hxg), exhibited significantly enhanced cellular uptake compared to Tat(49-57) and even to r9. Overall, a transporter has been developed that is superior to Tat(49-57), protease resistant, and more readily and economically prepared.
View details for Web of Science ID 000165476300022
View details for PubMedID 11087855
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Conjugation of arginine oligomers to cyclosporin A facilitates topical delivery and inhibition of inflammation
NATURE MEDICINE
2000; 6 (11): 1253-1257
Abstract
Many systemically effective drugs such as cyclosporin A are ineffective topically because of their poor penetration into skin. To surmount this problem, we conjugated a heptamer of arginine to cyclosporin A through a pH-sensitive linker to produce R7-CsA. In contrast to unmodified cyclosporin A, which fails to penetrate skin, topically applied R7-CsA was efficiently transported into cells in mouse and human skin. R7-CsA reached dermal T lymphocytes and inhibited cutaneous inflammation. These data establish a general strategy for enhancing delivery of poorly absorbed drugs across tissue barriers and provide a new topical approach to the treatment of inflammatory skin disorders.
View details for Web of Science ID 000165114800033
View details for PubMedID 11062537
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Synthesis and tumor-promoting activities of 12-epi-phorbol-12, 13-dibutyrate
BIOSCIENCE BIOTECHNOLOGY AND BIOCHEMISTRY
2000; 64 (11): 2429-2436
Abstract
12-Epi-phorbol-12,13-dibutyrate (1), the C12-epimer of the most frequently used phorbol ester probe, phorbol-12,13-dibutyrate (PDBu), has been synthesized from phorbol in 9 steps in order to investigate the structural requirements for tumor-promoting activity. Compound 1 showed about 100-fold weaker in vitro biological activities related to in vivo tumor promotion, Epstein-Barr virus early antigen (EBV-EA)-inducing ability, superoxide (O2-) generation-inducing ability, and binding to the protein kinase C (PKC) regulatory domain surrogate peptides. The results indicated that the beta-stereochemistry at position 12 of the phorbol skeleton is important for optimal activity. Binding selectivity to each PKC C1 domain of 1 was almost equal to that of PDBu.
View details for Web of Science ID 000165615900020
View details for PubMedID 11193412
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Synthesis and PKC isozyme surrogate binding of indothiolactam-V, a new thioamide analogue of tumor promoting indolactam-V
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
2000; 10 (18): 2087-2090
Abstract
To investigate the role of the amide group of (-)-indolactam-V (1) on PKC binding, we synthesized (-)-indothiolactam-V (2), a new thioamide analogue of 1, by microbial conversion using Streptomyces blastmyceticum. Compounds 2 and 1 showed similar binding affinities to conventional PKCs but 2 had lower affinities to novel PKCs, suggesting that novel PKCs recognize amide modifications more effectively than conventional PKCs.
View details for Web of Science ID 000089679900011
View details for PubMedID 10999477
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Synthesis and biological evaluation of a new class of bryostatin analogues: the role of the C20 substituent in protein kinase C binding
TETRAHEDRON LETTERS
2000; 41 (35): 6725-6729
View details for Web of Science ID 000089031200009
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Transition metal-catalyzed [6+2] cycloadditions of 2-vinylcyclobutanones and alkenes: A new reaction for the synthesis of eight-membered rings
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
2000; 122 (32): 7815-7816
View details for Web of Science ID 000088946100026
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Asymmetric total synthesis of (+)-aphanamol I based on the transition metal catalyzed [5+2] cycloaddition of allenes and vinylcyclopropanes
ORGANIC LETTERS
2000; 2 (15): 2323-2326
Abstract
A concise asymmetric total synthesis of (+)-aphanamol I is described, based on the transition metal catalyzed [5 + 2] allenyl-vinylcyclopropane cycloaddition. The key cycloaddition precursor is convergently assembled from (R)-(+)-limonene and cyclopropane diester through a novel decarboxylative dehydration reaction. The metal-catalyzed [5 + 2] cycloaddition of this precursor proceeds with complete chemo, endo/exo, and diastereoselectivity in 93% yield, representing an effective general route to bicyclo[5.3.0]decane derivatives.
View details for Web of Science ID 000088346400037
View details for PubMedID 10930274
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A new and practical five-carbon component for metal-catalyzed
Organic letters
2000; 2 (11): 1609-1611
Abstract
Described herein is an efficient preparative scale synthesis of 1-(2-methyoxyethoxy)-1-vinylcyclopropane and the investigation of the utility of this reagent as a new five-carbon component in metal-catalyzed [5 + 2] cycloadditions. A new cycloaddition procedure is also described that proceeds up to 12-fold faster and with 10-fold less catalyst than previously described, providing cycloheptenones in many cases in minutes and in isolated yields of 75-97%. The procedure is readily conducted on a small or large scale (up to 100 mmol thus far).
View details for PubMedID 10841491
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A new and practical five-carbon component for metal-catalyzed [5+2] cycloadditions: Preparative scale syntheses of substituted cycloheptenones
ORGANIC LETTERS
2000; 2 (11): 1609-1611
View details for Web of Science ID 000087292600029
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Synthesis and biological evaluation of bryostatin analogues: the role of the A-ring
TETRAHEDRON LETTERS
2000; 41 (7): 1007-1011
View details for Web of Science ID 000085357000005
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Bromoacetophenone-based photonucleases: Photoinduced cleavage of DNA by 4 '-bromoacetophenone-pyrrolecarboxamide conjugates
ORGANIC LETTERS
1999; 1 (13): 2117-2120
Abstract
[formula: see text] 4'-Bromoacetophenone derivatives which upon excitation can generate monophenyl radicals capable of hydrogen atom abstraction were investigated as photoinducible DNA cleaving agents. Pyrrolecarboxamide-conjugated 4'-bromoacetophenones were synthesized, and their DNA cleaving activities and sequence selectivities were determined.
View details for Web of Science ID 000084980700020
View details for PubMedID 10836065
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Transition metal-catalyzed [5+2] cycloadditions of 2-substituted-1-vinylcyclopropanes: Catalyst control and reversal of regioselectivity
ORGANIC LETTERS
1999; 1 (13): 2089-2092
View details for Web of Science ID 000084980700013
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Transition metal-catalyzed [5+2] cycloadditions with substituted cyclopropanes: First studies of regio- and stereoselectivity
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1999; 121 (44): 10442-10443
View details for Web of Science ID 000083719800034
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A new class of simplified phorbol ester analogues: Synthesis and binding to PKC and eta PKC-C1B (eta PKC-CPD2)
ORGANIC LETTERS
1999; 1 (7): 1009-1012
Abstract
[formula: see text] A unique class of simplified phorbol ester analogues is described for the first time. A highly efficient retro-annelation sequence was developed in order to remove the five-membered ring from the phorbol diterpene core, allowing access to BCD ring analogues of the phorbol esters. The binding of these analogues to protein kinase C (PKC) and the truncated peptide eta PKC-C1B (eta PKC-CRD2) is also reported.
View details for Web of Science ID 000085171900013
View details for PubMedID 10825954
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Synthesis and phorbol ester-binding studies of the individual cysteine-rich motifs of protein kinase D
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1999; 9 (17): 2487-2490
Abstract
To investigate the phorbol ester-binding properties of the individual cysteine-rich motifs of protein kinase D (PKD), the 52-mer peptides containing each cysteine-rich motif of PKD (PKD-C1A, PKD-C1B) have been synthesized. The [3H]phorbol-12,13-dibutyrate (PDBu) binding to PKD-C1A was affected drastically by incubation temperature while that to PKD-C1B was not. Scatchard analysis of [3H]PDBu binding to both PKD C1 peptides gave dissociation constants of 2.5 +/- 0.4 and 2.7 +/- 0.8 nM for PKD-C1A and PKD-C1B, respectively, indicating that the two cysteine-rich motifs of PKD are functionally equivalent like those of PKCgamma.
View details for Web of Science ID 000082476300007
View details for PubMedID 10498194
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The rational design of potential chemotherapeutic agents: Synthesis of bryostatin analogues
3rd Winter Conference on Medicinal and Bioorganic Chemistry
JOHN WILEY & SONS INC. 1999: 388–407
Abstract
The bryostatins are a unique family of cancer chemotherapeutic candidates isolated from marine bryozoa. While their molecular mode of action is not known, these macrolactones exhibit high affinities for protein kinase C (PKC) isozymes, compete for the phorbol ester binding site on PKC, and stimulate kinase activity in vitro and in vivo. Unlike the phorbol esters, they do not act as tumor promoters. Despite promising biological properties, the supply of these compounds is limited by the difficulty of their isolation from natural sources and their synthetic complexity. A new class of bryostatin analogues which retain the putative recognition domain of the bryostatins but are simplified through deletions and modifications in the C1-C14 spacer domain have been designed using computer models. A convergent synthesis has been realized for the production, in gram quantities, of these recognition and spacer domains whose coupling allows for the generation of a range of analogues. The final closure process involves a novel macrotransacetalization reaction which proceeds with complete stereoselectivity. The solution structures of two synthetic analogues were determined by NMR spectroscopy and found to be very similar to the previously reported structures of bryostatins 1 and 10. In addition, these structures appear to indicate that the stereochemistry of the C3 hydroxyl group plays a significant role in the conformation of the macrolactone. All analogues bound strongly to a mixture of PKC isozymes, and several exhibited significant levels of in vitro growth inhibitory activity against human cancer cell lines. Taken together, this work provides important steps toward the development and understanding of simplified, synthetically accessible analogues of the bryostatins as potential chemotherapeutic agents.
View details for Web of Science ID 000082385200006
View details for PubMedID 10502742
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Rhodium-catalyzed [5+2] cycloadditions of allenes and vinylcyclopropanes: Asymmetric total synthesis of (+)-dictamnol
ORGANIC LETTERS
1999; 1 (1): 137-139
View details for Web of Science ID 000083701300036
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Selective binding of bryostatin analogues to the cysteine rich domains of protein kinase C isozymes
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1999; 9 (12): 1687-1690
Abstract
Designed bryostatin analogues are assayed for binding affinity to individual cysteine rich domains of several protein kinase C (PKC) isozymes. These analogues exhibit significant selectivity for the PKCdelta-C1B peptide in terms of absolute affinity and the PKCdelta-C1A peptide in terms of relative affinity when compared to phorbol-12,13-dibutyrate.
View details for Web of Science ID 000080896500013
View details for PubMedID 10397502
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Transition metal-catalyzed [5+2] cycloadditions of allenes and vinylcyclopropanes: First studies of endo-exo selectivity, chemoselectivity, relative stereochemistry, and chirality transfer
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1999; 121 (22): 5348-5349
View details for Web of Science ID 000080854100038
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Solid-phase synthesis, mass spectrometric analysis of the zinc-folding, and phorbol ester-binding studies of the 116-mer peptide containing the tandem cysteine-rich C1 domains of protein kinase C gamma
BIOORGANIC & MEDICINAL CHEMISTRY
1999; 7 (6): 1213-1221
Abstract
Tumor-promoting phorbol esters activate protein kinase C (PKC) isozymes by binding to the zinc-finger like cysteine-rich domains in the N-terminal regulatory region. Our recent studies have revealed that only PKCgamma has two high affinity phorbol ester-binding domains, providing a structural blueprint for the rational design of PKCgamma-selective modulators for the treatment of neuropathic pain. To extend this approach, the 116-mer peptide containing the double cysteine-rich motifs of PKCgamma (gamma-C1A-C1B) has been synthesized for the first time using an Fmoc-solid phase strategy with a stepwise chain elongation. This peptide was purified by the reversed phase HPLC to give satisfactory mass data (MALDI-TOF-MS and ESI-TOF-MS). The peptide was successfully folded by zinc treatment and the folded peptide was analyzed intact under neutral conditions by ESI-TOF-MS. The multiple charge mass envelopes shifted to those of the lower mass charge state by addition of 4 molar equiv. ZnCl2, suggesting that gamma-C1A-C1B preserves some higher order structure by the zinc folding. Moreover, the mass spectrum of the zinc-folded peptide in the presence of EDTA clearly showed that gamma-C1A-C1B coordinates exactly four atoms of zinc. This zinc stoichiometry is identical to that of native PKCgamma. Scatchard analysis of the zinc-folded peptide revealed two binding sites of distinctly different affinities (Kd=6.0 +/- 1.5 and 47.0 +/- 6.6 nM) comparable to those reported by Quest and Bell for the GST fusion protein of gamma-C1A-C1B prepared by DNA recombination. These results indicate that gamma-C1A-C1B serves as an effective surrogate for native PKCgamma for the study of the structural characteristics of the binding recognition event and the design, discovery, and development of new PKCgamma-selective modulators.
View details for Web of Science ID 000081084000028
View details for PubMedID 10428394
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Mapping phorbol ester binding domains of protein kinase C (PKC): The design, synthesis and biological activity of novel phorbol ester dimers
SYNTHESIS-STUTTGART
1999: 1401-1406
View details for Web of Science ID 000082270900002
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Synthesis and biological evaluation of fully synthetic bryostatin analogues
TETRAHEDRON LETTERS
1998; 39 (47): 8625-8628
View details for Web of Science ID 000076750100018
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A formal synthesis of crinipellin B based on the arene-alkene meta-photocycloaddition reaction
TETRAHEDRON LETTERS
1998; 39 (47): 8589-8592
View details for DOI 10.1016/S0040-4039(98)01965-0
View details for Web of Science ID 000076750100009
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The transition metal-catalyzed intermolecular [5+2] cycloaddition: The homologous Diels-Alder reaction
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1998; 120 (42): 10976-10977
View details for Web of Science ID 000076693100023
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Synthesis and binding studies of the 116-mer peptide containing the double cysteine-rich motifs of protein kinase C gamma
TETRAHEDRON LETTERS
1998; 39 (43): 7943-7946
View details for Web of Science ID 000076338400033
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Molecular basis for protein kinase C isozyme-selective binding: The synthesis, folding, and phorbol ester binding of the cysteine-rich domains of all protein kinase C isozymes
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1998; 120 (36): 9159-9167
View details for Web of Science ID 000075954000006
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The first metal-catalyzed intramolecular [5+2] cycloadditions of vinylcyclopropanes and alkenes: Scope, stereochemistry, and asymmetric catalysis
TETRAHEDRON
1998; 54 (25): 7203-7220
View details for Web of Science ID 000073945500018
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The design, computer modeling, solution structure, and biological evaluation of synthetic analogs of bryostatin 1
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1998; 95 (12): 6624-6629
Abstract
The bryostatins are a unique family of emerging cancer chemotherapeutic candidates isolated from marine bryozoa. Although the biochemical basis for their therapeutic activity is not known, these macrolactones exhibit high affinities for protein kinase C (PKC) isozymes, compete for the phorbol ester binding site on PKC, and stimulate kinase activity in vitro and in vivo. Unlike the phorbol esters, they are not first-stage tumor promoters. The design, computer modeling, NMR solution structure, PKC binding, and functional assays of a unique class of synthetic bryostatin analogs are described. These analogs (7b, 7c, and 8) retain the putative recognition domain of the bryostatins but are simplified through deletions and modifications in the C4-C14 spacer domain. Computer modeling of an analog prototype (7a) indicates that it exists preferentially in two distinct conformational classes, one in close agreement with the crystal structure of bryostatin 1. The solution structure of synthetic analog 7c was determined by NMR spectroscopy and found to be very similar to the previously reported structures of bryostatins 1 and 10. Analogs 7b, 7c, and 8 bound strongly to PKC isozymes with Ki = 297, 3.4, and 8.3 nM, respectively. Control 7d, like the corresponding bryostatin derivative, exhibited weak PKC affinity, as did the derivative, 9, lacking the spacer domain. Like bryostatin, acetal 7c exhibited significant levels of in vitro growth inhibitory activity (1.8-170 ng/ml) against several human cancer cell lines, providing an important step toward the development of simplified, synthetically accessible analogs of the bryostatins.
View details for Web of Science ID 000074131900012
View details for PubMedID 9618462
View details for PubMedCentralID PMC22576
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Synthesis of the first members of a new class of biologically active bryostatin analogues
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1998; 120 (18): 4534-4535
View details for Web of Science ID 000073645600041
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First studies of the transition metal-catalyzed [5+2] cycloadditions of alkenes and vinylcyclopropanes: Scope and stereochemistry
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1998; 120 (8): 1940-1941
View details for Web of Science ID 000072368600048
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The chemistry-medicine continuum: Synthetic, computer, spectroscopic and biological studies on new chemotherapeutic leads
AFMC International Medicinal Chemistry Symposium (AIMECS 97)
INT UNION PURE APPLIED CHEMISTRY. 1998: 539–46
View details for Web of Science ID 000074838600004
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Towards the ideal synthesis
CHEMISTRY & INDUSTRY
1997: 765-?
View details for Web of Science ID A1997YA13200021
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Comparison of chemical characteristics of the first and the second cysteine-rich domains of protein kinase C gamma
BIOORGANIC & MEDICINAL CHEMISTRY
1997; 5 (8): 1725-1737
Abstract
Protein kinase C (PKC) is a key enzyme family involved in cellular signal transduction. The binding of endogenous diacyl glycerol (DAG) to the cysteine-rich domain (CRD) of PKC is associated with normal cell signaling and function. In contrast, the binding of exogenous phorbol esters to the CRD of PKC is considered to be a key initiating event in tumor promotion. Conventional PKC isozymes (PKC alpha, beta I, beta II, and gamma) contain two CRDs, both of which are candidates for the phorbol ester binding site. In order to elucidate the binding requirements of phorbol esters and to obtain information on the phorbol ester binding site in native PKC gamma, several key chemical characteristics of the first and the second CRDs consisting of ca. 50 amino acids of rat PKC gamma (gamma-CRD1 and gamma-CRD2) were examined. In the presence of Zn2+ and phosphatidylserine (PS), both CRDs gave similar Kd values (65.3 nM for gamma-CRD1, 44.1 nM for gamma-CRD2) in phorbol 12,13-dibutyrate (PDBu) binding assays. In comparison, the binding affinity of PDBu for native rat PKC gamma was found to be 6.8 nM. Zn2+ was shown to play an important role in the folding and PDBu binding of both CRDs. A Zn(2+)-induced conformational change was observed for the first time by CD spectroscopic analysis of the complexed and uncomplexed CRDs. Relative to the pronounced Zn2+ effect, most divalent first row transition metal ions along with Ca2+, Mg2+, and Al3+ were ineffective in folding either CRD. Notably, however, Co2+ exhibited a gamma-CRD1-selective effect, suggesting that metal ions, not unlike extensively used organic probes, might also become effective tools for controlling isozyme selective activation of PKC. Moreover, group Ib (Cu2+ and Ag+) and group IIb element ions other than Zn2+ (Cd2+ and Hg2+) were found to abolish PDBu binding of both CRDs. Importantly, these inhibitory effects of Cu2+, Ag+, and Cd2+, and Hg2+ were also observed with native PKC gamma. These results indicate that recent reports on the modulation of conventional PKC by heavy metal ions could be explained by their coordination to the CRDs. While the similar affinities of gamma-CRD1 and gamma-CRD2 for PDBu suggest that either site qualifies as the PDBu binding site, new molecular probes of these CRD3 have now been identified that provide information on the preferred site. These novel ligands (5a and 5b) were synthesized by aza-Claisen rearrangement of (-)-N13-desmethyl-N13-allylindolactam-G (4). These compounds did not significantly affect the specific PDBu binding of gamma-CRD1 but did inhibit that of gamma-CRD2 with similar potency to (-)-indolactam-V. Moreover, these new probes did not significantly inhibit the PDBu binding of native PKC gamma. (-)-Indolactam-V itself bound almost equally to gamma-CRD1, gamma-CRD2, and native PKC gamma. These results suggest that the major PDBu binding site in native PKC gamma is the first CRD, not the second CRD, unlike the novel PKCs.
View details for Web of Science ID A1997XX51600022
View details for PubMedID 9313873
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Synthesis of novel taxol analogs and evaluation of their biological activities
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1997; 7 (14): 1941-1944
View details for Web of Science ID A1997XP63900028
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Protein kinase C regulatory domain surrogate peptides: Effects of metal ions on folding, phorbol ester-binding, and selectivity
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1997; 7 (8): 965-970
View details for Web of Science ID A1997WY45300003
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Synthesis of 1-(2-naphthoyl) benzotriazoles as photoactivated DNA cleaving agents
ARCHIVES OF PHARMACAL RESEARCH
1997; 20 (2): 197-199
View details for DOI 10.1007/BF02974011
View details for Web of Science ID A1997WW27400017
View details for PubMedID 18975202
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The pinene path to taxanes .6. A concise stereocontrolled synthesis of taxol
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1997; 119 (11): 2757-2758
View details for Web of Science ID A1997WN85500031
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The pinene path to taxanes .5. Stereocontrolled synthesis of a versatile taxane precursor
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1997; 119 (11): 2755-2756
View details for Web of Science ID A1997WN85500030
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Synthesis and characterization of the first cysteine-rich domain of novel protein kinase C
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1997; 7 (2): 117-122
View details for Web of Science ID A1997WE78500005
- Sequence-specific DNA cleavage by conjugates ofbenzotriazoles and minor groove binders. JACS 1997: 7611-7612.
- The first formal asymmetric synthesis of phorbol. JACS 1997: 7987-7898
- The pinene path to taxanes .6. A concise stereocontrolled synthesis of taxol. JACS 1997: 2757-2758.
- The first synthesis of a daphnane diterpene: the enantiocontrolled total synthesis of (+)-resiniferatoxin. JACS 1997: 12976-12977.
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Synthesis and biological activities of new conformationally restricted analogues of (-)-indolactam-V: Elucidation of the biologically active conformation of the tumor-promoting teleocidins
JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
1996; 118 (44): 10733-10743
View details for Web of Science ID A1996VR41900008
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Synthesis and characterization of new photolabile phorbol esters for affinity labeling of protein kinase C
JOURNAL OF ORGANIC CHEMISTRY
1996; 61 (6): 2164-2173
View details for Web of Science ID A1996UB20500047
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Synthesis and characterization of the second cysteine-rich region of mouse skin PKC eta
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1996; 6 (4): 353-356
View details for Web of Science ID A1996TX41300003
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Introduction: Frontiers in Organic Synthesis.
Chemical reviews
1996; 96 (1): 1–2
View details for PubMedID 11848741
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The Pinene Path to Taxanes. 4. Approaches to Taxol and Taxol Analogs through Elaboration of Aromatic C-Ring Precursors.
The Journal of organic chemistry
1996; 61 (22): 7662–63
View details for PubMedID 11667717
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THE PINENE PATH TO TAXOL - READILY ACCESSIBLE A-RING BUILDING-BLOCKS BASED ON NOVEL ALKYLLITHIUM AND ALKENYLLITHIUM REAGENTS WITH INTERNAL CARBONYL GROUPS
TETRAHEDRON LETTERS
1995; 36 (40): 7181-7184
View details for Web of Science ID A1995RX65300005
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TOWARD THE SYNTHESIS OF TAXOL AND ITS ANALOGS - INCORPORATION OF NONAROMATIC C-RINGS IN THE PINENE PATHWAY
TETRAHEDRON LETTERS
1995; 36 (28): 4939-4942
View details for Web of Science ID A1995RJ58300006
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SYNTHESIS AND BIOLOGICAL-ACTIVITIES OF NEW CONFORMATIONALLY FIXED ANALOGS OF (-)-INDOLACTAM-V, THE CORE STRUCTURE OF TUMOR-PROMOTING TELEOCIDINS
BIOORGANIC & MEDICINAL CHEMISTRY LETTERS
1995; 5 (5): 453-458
View details for Web of Science ID A1995QM74100007
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THE INTRAMOLECULAR ADDITION OF SILYLATED ALKYNES TO ALDEHYDES - METHODOLOGY FOR THE CONSTRUCTION OF CYCLIC ENEDIYNES AND ITS APPLICATION TO DYNEMICIN ANALOGS
TETRAHEDRON LETTERS
1995; 36 (2): 209-212
View details for Web of Science ID A1995QA28200006
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IDENTIFICATION, ACTIVITY, AND STRUCTURAL STUDIES OF PEPTIDES INCORPORATING THE PHORBOL ESTER-BINDING DOMAIN OF PROTEIN-KINASE-C
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1995; 92 (1): 239-243
Abstract
The family of homologous enzymes known as protein kinase C (PKC) has been the object of intense interest because of its crucial role in cellular signal transduction. Although considerable information about the activation of PKC has been gained through structure-activity, molecular modeling, and synthetic studies of both natural and designed activators, information about the structure of PKC itself has been limited by its large size and requirement for phospholipid cofactors. Additionally, difficulties in the purification of truncated mutants of PKC have thus far prevented their analysis by nuclear magnetic resonance (NMR) or x-ray crystallographic methods. We describe the identification, synthesis, ligand-binding analysis, cofactor requirements, and preliminary NMR evaluation of two subdomains (peptides B and C) of the regulatory domain of PKC-gamma. Peptides B and C bind [3H]phorbol 12,13-dibutyrate with good affinity (Kd = 6.4 microM and 414 nM, respectively) in the presence of phosphatidylserine. In comparison, the binding affinity of [3H]phorbol 12,13-dibutyrate for PKC was found to be 2.6 nM. Like PKC itself, these peptides also recognize other PKC activators, including dioctanoylglycerol and teleocidin B-4, and exhibit an ability to differentiate phorbol ester from its C-4 epimer. NMR studies of PKC subdomains are also described, indicating that both peptides B and C are well behaved in solution and do not exhibit any concentration-dependent changes. Finally, these studies reveal that peptide B becomes conformationally ordered only in the presence of phospholipid, suggesting that the regulatory domain of PKC itself might be organized for activation only when associated with the lipid bilayer, where its activator (diacylglycerol) is encountered.
View details for Web of Science ID A1995QB23800049
View details for PubMedID 7816824
View details for PubMedCentralID PMC42853
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THE PINENE PATH TO TAXANES - GENESIS AND EVOLUTION OF A STRATEGY FOR SYNTHESIS
Symposium on Taxane Anticancer Agents - Basic Science and Current Status, at the 207th National Meeting of the American-Chemical-Society
AMER CHEMICAL SOC. 1995: 326–339
View details for Web of Science ID A1995BB96Q00024
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A 2ND-GENERATION PHOTOCHEMICALLY ACTIVATABLE DYNEMICIN ANALOG - A CONCISE SYNTHESIS AND DNA CLEAVAGE STUDIES
SYNTHESIS-STUTTGART
1994: 1278-1282
View details for Web of Science ID A1994QA02500010
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THE SYNTHESIS AND CHEMISTRY OF A SIMPLIFIED, FUNCTIONAL ANALOG OF NEOCARZINOSTATIN CHROMOPHORE - IDENTIFICATION OF AN INTRAMOLECULAR 1,5-HYDROGEN ATOM-TRANSFER RELEVANT TO THE MECHANISM AND CLEAVAGE SELECTIVITY OF DIYL-BASED DNA-CLEAVING AGENTS
TETRAHEDRON
1994; 50 (5): 1419-1434
View details for DOI 10.1016/S0040-4020(01)80627-X
View details for Web of Science ID A1994MV16200009
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A PHOTOCHEMICALLY TRIGGERED DNA-CLEAVING AGENT - SYNTHESIS, MECHANISTIC AND DNA CLEAVAGE STUDIES ON A NEW ANALOG OF THE ANTITUMOR ANTIBIOTIC DYNEMICIN
JOURNAL OF ORGANIC CHEMISTRY
1993; 58 (22): 5867-5869
View details for DOI 10.1021/jo00074a001
View details for Web of Science ID A1993MD98500001
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SYNTHESIS AND BINDING OF PHOTOAFFINITY LIGAND CANDIDATES FOR PROTEIN-KINASE-C
JOURNAL OF ORGANIC CHEMISTRY
1993; 58 (16): 4179-4181
View details for DOI 10.1021/jo00068a001
View details for Web of Science ID A1993LV42500001
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TOWARD THE SYNTHESIS OF THE TAXOL C,D RING-SYSTEM - PHOTOLYSIS OF ALPHA-METHOXY KETONES
TETRAHEDRON
1992; 48 (34): 7033-7048
View details for Web of Science ID A1992JL03800007
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STUDIES ON DNA-CLEAVING AGENTS - COMPUTER MODELING ANALYSIS OF THE MECHANISM OF ACTIVATION AND CLEAVAGE OF DYNEMICIN OLIGONUCLEOTIDE COMPLEXES
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1991; 88 (19): 8835-8839
Abstract
Dynemicin A is a recently identified antitumor antibiotic. Upon activation, dynemicin is reported to cause double-stranded cleavage of DNA, putatively through the intermediacy of a diradical. Computer modeling of this activation and cleavage process is described herein as part of an effort to establish a structural hypothesis for this mechanistic sequence and for the design of simple analogues. Intercalation complexes of duplex dodecamers [d(CGCGAATTCGCG)]2 and [d(GC)6]2 with both enantiomers of dynemicin and of all related mechanistic intermediates are evaluated. Examination of these structures shows that cycloaromatization of dynemicin to a diradical intermediate results in the rotation of the diradical-forming subunit with respect to the intercalation plane that is of an opposite sense for the two dynemicin enantiomers. In addition, the activation of the (2S) enantiomer of dynemicin occurs by a less restricted approach trajectory than the corresponding (2R) enantiomer. In all complexes, the 5'-3' strand is at least 1 A closer than the 3'-5' strand to the diyl intermediate. As a result, complexes are produced in which the diyl moiety is aligned along [(2S)] or across [(2R)] the minor groove, leading to different predictions for the selectivity of radical-initiated, oxidative lesion of DNA. Molecular dynamics simulations are found to support these predictions, including the 3-base-pair offset cleavage reported for dynemicin.
View details for Web of Science ID A1991GH80500114
View details for PubMedID 1924343
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MODELING OF THE BRYOSTATINS TO THE PHORBOL ESTER PHARMACOPHORE ON PROTEIN KINASE-C
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1988; 85 (19): 7197-7201
Abstract
The bryostatins are macrocyclic lactones that represent an additional structural class of potent activators of protein kinase C. These marine animal biosynthetic products are of unusual interest because they induce only a subset of the biological responses induced by the phorbol esters. We have now determined the binding affinities of naturally occurring and semisynthetic bryostatins for protein kinase C by competition analysis with [26-3H]bryostatin 4 as the radioactive ligand. Esterification of the hydroxyl group at C26 caused dramatic loss of activity as did inversion of the asymmetric center at this position. In contrast, neither of the ester groups at C7 and C20 had a major influence on activity. Computer modeling of the phorbol esters, related diterpenes, and indole alkaloids suggested that the C20, C9, and C4 oxygens of phorbol represented critical elements of the phorbol ester pharmacophore. The C26 oxygen of the bryostatins, together with the C1 and C19 oxygens, gave an excellent spatial correlation with this model, with a root-mean-square deviation of 0.16 A (compared to 0.10-0.35 A among phorbol-related diterpenes). The extension of the phorbol ester pharmacophore model to the bryostatins and its agreement with the structure-activity relations for the bryostatin class of compounds provide additional support for the validity of the model.
View details for Web of Science ID A1988Q358500033
View details for PubMedID 3174627
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ANALYSIS OF THE PHORBOL ESTER PHARMACOPHORE ON PROTEIN-KINASE-C AS A GUIDE TO THE RATIONAL DESIGN OF NEW CLASSES OF ANALOGS
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
1986; 83 (12): 4214-4218
Abstract
The diterpene diester phorbol 12-myristate 13-acetate and the alkaloid teleocidin B are structurally unrelated natural products that display similar potent irritant and tumor-promoting activities. Computer modeling of these and other structural classes of tumor promoters show a marked similarity in the relative positions of certain heteroatoms and hydrophobic groups. For phorbol this mapping consists of the C-4, C-9, and C-20 hydroxyl groups as well as a hydrophobic region filled by a long-chain acyl functionality attached to either the C-12 or the C-13 positions. Diacylglycerols, thought to be the endogenous activators of the major phorbol ester receptor protein kinase C likewise fit this model in a stereospecific fashion. As an initial test of the utility of the model, members of a new and simplified class of activators were synthesized that possess the predicted essential structural features. These compounds all inhibited specific phorbol ester binding to protein kinase C, albeit with low affinity (10-60 microM); further analysis of one derivative, decylhydroxylindole, confirmed that the inhibition of phorbol ester binding was competitive. This same derivative inhibited epidermal growth factor binding in intact Swiss 3T3 cells and studies with another derivative showed phosphorylation of a 40-kDa protein in platelets. Both of these in vivo responses are characteristic of phorbol esters.
View details for Web of Science ID A1986C835000023
View details for PubMedID 3086877