Total Synthesis of (-)-Gephylotoxin 223AB via Asymmetric 1,3-Dipolar Cycloaddition

点击翻译按钮获取中文摘要

Asymmetric 1,3-dipolar cycloaddition of nitrones by using a chiral allyl ether as a dipolarophile and application to an enantioselective synthesis of (-)-coniine and (+)-monomorine I has been investigated. The cyclic and acyclic nitrones were allowed to react with (s)-3-benzyloxy-1-heptene, resulting in the preferential formation (3:1) of the (2R,3aS)-and (3S,5R)-isoxazolidine derivatives, respectively, predicted by application of the inside alkoxy more reactive conformation in a transition state. These cycloadducts were enantiomerically converted to (-)-coniine and (+)-monomorine I,respectively.