1,3-Dimethyl-2-nitrobenzene was converted to the key intramolecular Friedel–Crafts intermediate 24 in ten steps. Treatment of 24 with TiCl4 produced tricyclic enone 25 in 61%–75% yield, having the requisite trans relationship of the two angular methyl groups and many of the salient features of the dolastane diterpenes. The structure of enone 25 was verified by X-ray crystallography analysis. Cyclization product 25 permitted the facile synthesis of (±)-14-epi-hydroxydolasta-1(15),7,9-triene and (±)-7-epi-acetoxy-14-epi-hydroxydolasta-1(15),8-diene, which are detailed in this article.
1,3-二甲基-2-
硝基苯被转化为关键的分子内Friedel-Crafts中间体24,经过十个步骤。用TiCl
4处理24产生
三环烯酮25,收率为61%–75%,具有两个角甲基的必需的反式关系和多个dolastane二萜的显著特征。通过X射线晶体学分析验证了烯酮25的结构。环化产物25促进了(±)-14-epi-hydroxydolasta-1(15),7,9-
三烯和(±)-7-epi-acetoxy-14-epi-hydroxydolasta-1(15),8-二烯的简便合成,这些在本文中有详细描述。