The synthesis of the decalin sub-unit 2 of (+)-pyripyropene A 1 (a key intermediate in the first total synthesis) is described. The key step involves a biomimetic epoxy-olefin cyclisation using an allylsilane as the terminating group. Whilst attempts to cyclise epoxy alcohol 6 were unfruitful, cyclisation of the protected epoxy benzyl ether 7 using BF3·OEt2 was successful, yielding bicyclic ester 25. Isomerisation of the exocyclic double bond into conjugation with the ester group proved to be problematic, although successful conditions were ultimately found.
本文介绍了 (+)-pyripyropene A 1 的
癸醛亚基 2(第一次总合成的关键中间体)的合成过程。关键步骤包括使用烯丙基
硅烷作为终止基团进行仿
生物环氧烯烃环化。虽然环化环氧醇 6 的尝试没有结果,但使用
BF3-OEt2 环化受保护的环氧苄基醚 7 却取得了成功,得到了双环酯 25。尽管最终找到了成功的条件,但外环双键与酯基共轭的异构化仍存在问题。