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Unified Total Synthesis of Five Bufadienolides

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journal contribution
posted on 26.10.2020, 16:16 by Shinsuke Shimizu, Koichi Hagiwara, Hiroaki Itoh, Masayuki Inoue
We report a unified total synthesis of five bufadienolides: bufalin (1), bufogenin B (2), bufotalin (3), vulgarobufotoxin (4), and 3-(N-succinyl argininyl) bufotalin (5). After the steroidal ABCD ring 8 was produced, the D ring was cross-coupled with a 2-pyrone moiety and stereoselectively epoxidized to generate 6. TMSOTf promoted a stereospecific 1,2-hydride shift from 6 to establish the β-oriented 2-pyrone of 19. Functional group manipulations from 19 furnished 15, which potently inhibited cancer cell growth.