title: Enantioselective Synthesis of Both Epimers at C-21 in the Proposed Structure of Cytotoxic Macrolide Callyspongiolide.
abstract: Both epimers at C-21 in the proposed structure of (+)-callyspongiolide have been synthesized in a convergent and enantioselective manner. The 14-membered macrolide with a sensitive C2-C3 cis-olefin functionality was installed by a Yamaguchi macrolactonization of hydroxyl alkynoic acid followed by hydrogenation over Lindlar's catalyst. The C5 methyl stereocenter was constructed by a ring-closing olefin metathesis followed by addition of methyl cuprate to an α,β-unsaturated δ-lactone. Other key reactions are chiral Corey-Bakshi-Shibata (CBS) reduction and Sonogashira coupling to conjoin the macrocyclic core and side chain.
authors.affiliation: Department of Chemistry and Department of Medicinal Chemistry, Purdue University , 560 Oval Drive, West Lafayette, Indiana 47907, United States.
authors.forename: Arun K
authors.initials: AK
authors.lastname: Ghosh
authors.affiliation: Department of Chemistry and Department of Medicinal Chemistry, Purdue University , 560 Oval Drive, West Lafayette, Indiana 47907, United States.
authors.forename: Luke A
authors.initials: LA
authors.lastname: Kassekert
mesh_terms: D002384:Catalysis; D006865:Hydrogenation; D018942:Macrolides / Q000138:chemical synthesis*; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D018942:Macrolides; C588104:callyspongiolide