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Studies on asymmetric total synthesis of (-)-β-hydrastine via a chiral epoxide ring-opening cascade cyclization
Jihui Li1, Tianxiao Wu1, Xinjing Song1
1Key Laboratory of Structure-Based Drug Design & Discovery of Ministry of Education, Shenyang Pharmaceutical University Shenyang 110016 People's Republic of China medchemzhao@163.com.
Abstract:
Herein, facile and enantioselective approaches to synthesize the core phthalide tetrahydroisoquinoline scaffold of (-)-β-hydrastine via both a CF3COOH-catalyzed (86% ee) and KHMDS-catalyzed (78% ee) epoxide ring-opening/transesterification cascade cyclization from chiral epoxide under very mild conditions are described. The key elements include a highly enantioselective epoxidation using the Shi ketone catalyst and an intramolecular CF3COOH-catalyzed cascade cyclization in one pot, and a late-stage C-3' epimerization under MeOK/MeOH conditions as the key steps to achieve the first total synthesis of (-)-β-hydrastine (up to 81% ee).
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