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13-Step Total Synthesis of Atropurpuran
- Xie, Shengling, Chen, Gui, Yan, Hao, Hou, Jieping, He, Yongping, Zhao, Tongyun, Xu, Jing
- Journal of the American Chemical Society 2019 v.141 no.8 pp. 3435-3439
- diterpenoid alkaloids, moieties, regioselectivity
- Herein, we report a concise total synthesis of atropurpuran, a unique and synthetically challenging pentacyclic diterpene that bears a tetracyclo[18.104.22.168⁴,⁹.0⁴,¹²]-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[22.214.171.124⁴,⁹.0⁴,¹²]-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.