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Enantioselective Total Syntheses of Kuwanon X, Kuwanon Y, and Kuwanol A
- Gao, Lei, Han, Jianguang, Lei, Xiaoguang
- Organic letters 2016 v.18 no.3 pp. 360-363
- Lewis acids, biomimetics, boron, catalytic activity, chemical structure, cycloaddition reactions, enantioselectivity, organic compounds
- The first enantioselective total syntheses of (−)-kuwanon X, (+)-kuwanon Y, and (+)-kuwanol A have been accomplished by using asymmetric Diels–Alder cycloaddition promoted by chiral VANOL or VAPOL/boron Lewis acid. The biosynthesis-inspired asymmetric Diels–Alder cycloaddition shows high exo selectivity (exo/endo = 13/1), which was unprecedented in the previous total syntheses of related prenylflavonoid Diels–Alder natural products. An acid catalyzed intramolecular ketalization process enabled a biomimetic transformation to construct the polycyclic skeleton of kuwanol A efficiently.