An enantioselective total synthesis of pentacyclic proaporphine alkaloid (−)‐misramine has been achieved. The synthetic route features a Pictet‐Spengler cyclization to construct the fused B and C rings and a sequence of Baeyer‐Villiger oxidation, Pinnick oxidation, and pinacol‐type cyclization to install the α‐hydroxy ketal moiety. The absolute configuration of the pentacyclic framework was elucidated by X‐ray single‐crystal analyses of (−)‐11‐demethoxymisramine.

中文翻译：

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对映选择性全合成五环普鲁啡碱生物碱（-）-米沙明

已实现对映选择性的五环前胃啡肽生物碱（-）-misramine的合成。合成路线具有Pictet-Spengler环化作用以构建稠合的B和C环，以及一系列Baeyer-Villiger氧化，Pinnick氧化作用和Pinacol型环化作用以安装α-羟基缩酮部分。通过（-）-11-去甲氧基三聚氰胺的X射线单晶分析阐明了五环骨架的绝对构型。