Enantioselective Total Syntheses of (+)-Ganocin A and (-)-Cochlearol B
Tomoya Mashiko1, Yuta Shingai1, Jun Sakai1
1Department of Synthetic Medicinal Chemistry, Faculty of Pharmaceutical Sciences, Hoshi University, 2-4-41 Ebara, Shinagawa-ku, Tokyo 142-8501, Japan.
Abstract:
Herein, we report the total syntheses of (+)-ganocin A and (-)-cochlearol B, featuring pentacyclic skeletons, in optically active forms. We utilized asymmetric Corey-Bakshi-Shibata reduction, phenolic oxidative cyclization, the intramolecular radical cyclization-benzylic oxidative cyclization sequence, and intramolecular [2 + 2] photocycloaddition. These key steps enabled enantioselective access with the longest linear sequence of 17 steps and 9% overall yield for (+)-ganocin A and with 16 steps and 9% overall yield for (-)-cohlearol B.
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