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13-Step Total Synthesis of Atropurpuran

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journal contribution
posted on 13.02.2019 by Shengling Xie, Gui Chen, Hao Yan, Jieping Hou, Yongping He, Tongyun Zhao, Jing Xu
Herein, we report a concise total synthesis of atropurpuran, a unique and synthetically challenging pentacyclic diterpene that bears a tetracyclo­[,9.04,12]-tridecane skeleton that is unprecedented among natural terpenes. This 13-step approach features a strategy that include early stage rapid skeleton formation and the late-stage introduction of reactive functional groups, thus allowed a high overall synthetic efficiency with minimal use of PGs. The key transformations of our work include a facile construction of the spiro[5.5]­undecane moiety through an ring-closing enyne metathesis reaction and an efficient formation of the tetracyclo­[,9.04,12]-tridecane scaffold via an regioselective double oxidative dearomatization/intramolecular Diels–Alder reaction cascade. This efficient approach should also inspire further advances in the synthesis of related complex diterpenes and diterpenoid alkaloids.