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Synthesis of Discodermolides Useful for Investigating Microtubule Binding and Stabilization Melissa G. Morris CHEM 635 February 12, 2013 Hung, D. T.; Nerenberg, J. B.; Schreiber, S. L. J. Am. Chem. Soc. 1996, 118, 11054-11080
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Stuart L. Schreiber, Ph.D. Born February 6, 1956 B.A. in chemistry from UVA, 1977 Ph.D. from Harvard University Joined Yale University faculty in 1981 Promoted to associate professor in 1984 Full Professor in 1986 Retuned to Harvard in 1988–present Morris Loeb Professor of Chemistry and Biology Director of Chemistry Biology A Founding Member of the Broad Institute of Harvard and MIT. His research is focused in chemical biology >460 publications
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History 1990–isolated by Gunasekera and co-workers at the Harbor Branch Oceranographic Institute from the deep-sea marine sponge Discodermolide dissoluta 1993–Schreiber and co-workers reported the first total synthesis of Discodermolide, but unfortunately the unantural antipode, (-)- Discodermolide They also determined the absolute stereochemistry, something Gunasekera was unable to determine
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Retro-synthesis 2 = C-C 7 3 = C 9 -C 15 4 = C 16- C 24
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Forward Synthesis Synthesis of C1-C7 Synthesis of C9-C15
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Forward Synthesis Cont. Synthesis of C16-C24
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Combining the Fragments Reduction of acetylene was too problematic in the presence of the terminal diene C16-C24 C9-C15
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Revision of Coupling
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…doesn’t work! The Final Step…
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Final Step Revised
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Stereochemistry His original total synthesize provided: ([ ] 20 D = -13.0(c = 0.6, methanol)). The current synthesis provided: ([ ] 20 D = +14.0 (C = 0.6, methanol)), which was obtained via biological characterization
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Synthesizing Derivatives for Biological Studies Purpose: To further characterize the interactions between Discodermolide and its receptor How : Synthesize an array of targets that can be analyzed when subjected in vivo Why: Disocdermolide comprises numerous biological properties: Immunisuppressive Antiproliferative/antimitotic Potent microtubule-stabilizing agent
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Structural Variants for Studying Interactions with Discodermolide Receptor Before these variants were made, truncated version of Discodermolide were tested to see if the full length is needed for receptor recognition
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Structural Variants Cont. 32 and 35 were not active in vivo, suggesting that the full length of Discodermolide was necessary for receptor recognition
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Binding Reagent Syntheses
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Binding Reagents Cont.
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SubstrateProductR1R1 R2R2 IC 50 27b 50a PhS S-Me6nM 27a 50b PhS S-Me4nM 26b 51 PhS H4nM
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Summary of Reagents and Activities no.IC 50 a (nM)no.IC 50 a (nM) 11a6837 2311094570 31c3001050a6 41b1150b4 53212514 6351359 73670 Final Biological Assay Results
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Conclusion A total synthesis of (+)-Discodermolide in 36 steps, with an overal yield of 4.3% over 24 steps (the longest linear sequence) Discodermolide remains the most potent natural promoter of tubulin assembly
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(Extra) Synthesis of 59
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