A concise and efficient approach to the core of the C18/C19 diterpenoid alkaloids and phomopsterone B is reported. Both syntheses share the same iron-catalyzed intramolecular [5+2] cycloaddition to assemble the tricyclo[6.3.1.01,6]]dodecane skeleton. The following ­approach to the 6/5/6/7 tetracyclic core scaffold of C18/C19 diterpenoid alkaloids features a regioselective Grignard addition/thermal Claisen rearrangement/RCM cyclization. Meanwhile the synthetic steps to access the spiro 6/5/6 tricyclic subunits of phomopsterone B were characterized as intramolecular aldol reaction, Wacker oxidation, and Criegee ­reaction.

中文翻译：

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铁催化分子内[5+2]环加成合成多环骨架

报道了 C18/C19 二萜生物碱和 phomopsterone B 核心的简洁有效的方法。两种合成都共享相同的铁催化分子内 [5+2] 环加成以组装三环 [6.3.1.01,6]] 十二烷骨架。C18/C19 二萜生物碱的 6/5/6/7 四环核心支架的以下方法具有区域选择性格氏加成/热克莱森重排/RCM 环化。同时，合成类黄酮 B 的螺 6/5/6 三环亚基的合成步骤被表征为分子内醛醇反应、Wacker 氧化和 Criegee 反应。