Pallimamine (1) is a structurally unique quaternary carbon-containing pentacyclic tetrahydroberberine. Synthesis of key C13-disubstituted tetrahydroberberine intermediates, as separable diastereomeric isomers, was achieved using a formal [4 + 2] cycloaddition of 4-methylhomophthalic anhydrides with 6,7-dimethoxy-3,4-dihydroisoquinolin-8-ol. Intramolecular Mitsunobu reactions provided installation of the dihydropyran generating pallimamine (1) and its non-natural diastereomer epi-pallimamine (33).

中文翻译：

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五环四氢小檗碱pallimamine和epi-pallimamine的合成

Pallimamine ( 1 ) 是一种结构独特的含季碳的五环四氢小檗碱。使用 4-methylhomophthalic 酸酐与 6,7-dimethoxy-3,4-dihydroisoquinolin-8-ol 的正式 [4 + 2] 环加成反应，合成了关键的 C13-二取代四氢小檗碱中间体，作为可分离的非对映异构体。分子内 Mitsunobu 反应提供了生成二氢吡喃的 pallimamine ( 1 ) 及其非天然非对映异构体epi -pallimamine ( 33 ) 的安装。