A One-Pot Intramolecular Tandem Michael–Aldol Annulation Reaction for the Synthesis of Chiral Pentacyclic Terpenes
A One-Pot Intramolecular Tandem Michael–Aldol Annulation Reaction for the Synthesis of Chiral Pentacyclic Terpenes
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DOI：
10.1055/s-0039-1690521
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发表时间：
2019-08
期刊：
影响因子：
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通讯作者：
Jianyu Lu;Serkan Koldaş;Huafang Fan;J. Desper;V. Day;D. Hua
中科院分区：
文献类型：
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作者：
Jianyu Lu;Serkan Koldaş;Huafang Fan;J. Desper;V. Day;D. Hua
摘要 具有6,6,6-三环骨架和3,3-二甲基-7-氧代辛基侧链的手性三环萜烯在碱性条件下发生双闭环反应，通过分子内迈克尔加成和羟醛缩合，以4:3的比例生成两个手性五环萜烯。在最初的迈克尔成环反应中引入了三个新的立体中心。在两种五环萜烯的C17处分别立体选择性安装乙氧基羰基，得到相应的具有七个立体中心的高功能化五环萜类化合物。通过X射线晶体学分析确定了关键中间体和产品的结构和立体化学。提出了一种机制来解释迈克尔环化反应中的立体化学。
Abstract A chiral tricyclic terpene possessing a 6,6,6-tricyclic framework and a 3,3-dimethyl-7-oxooctylidenyl side chain undergoes a double ring-closing reaction to give two chiral pentacyclic terpenes in a ratio of 4:3 via an intramolecular Michael addition followed by aldol condensation under basic conditions. Three new stereogenic centers are introduced in the initial Michael annulation reaction. Stereoselective installation of an ethoxycarbonyl group at C17 of the two pentacyclic terpenes separately gives the corresponding highly functionalized pentacyclic terpenoids with seven stereogenic centers. The structures and stereochemistry of key intermediates and products are established through X-ray crystallographic analysis. A mechanism is proposed for explaining the stereochemistry in the Michael annulation reaction.