A formal semisynthesis of the marine steroid demethylgorgosterol was realized by the synthesis of an advanced ketone intermediate. The intermediate was synthesized in ten steps, starting from commercially available stigmasterol. An overall yield of 27 % was achieved. The key step was a stereoselective cyclopropanation reaction with 82 % yield, a trans/cis ratio of 89 : 11, and dr_trans of >99 : 1.

中文翻译：

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利用立体选择性分子间环丙烷化反应形式的脱甲基庚固醇的形式半合成

通过合成高级酮中间体，可以实现海洋类固醇脱甲基庚固醇的正式半合成。从市售的豆甾醇开始十步合成中间体。总产率达到27％。关键步骤是立体选择性环丙烷化反应，收率为82％，反式/顺式比为89：11，dr_反式> 99：1。