Synthetic Applications of Conjugated Nitrones, 5 A Novel Entry to the 13-Azasteroid System
作者:Eloisa Lopez-Calle、Johannes Höfler、Wolfgang Eberbach
DOI:10.1002/jlac.199619961120
日期:1996.11
of the trimethylsilyl substituent by the sterically more demanding triisopropylsilyl group the formation of 15c was accomplished as expected. Upon thermally induced 1,7-cyclization of the nitrones 16/26 a multistep rearrangement of the primary cycloallenic intermediates takes place resulting in the formation of the corresponding 6,6,6,5- and 6,6,5,5-ring steroids (17/27 and 18/28) in 55–86% yield.
描述了合成13-氮杂甾体和C-nor-13-氮杂甾体衍生物(17/18型)以及4,13-二氮杂类似物27/28的方法。为了构建四环化合物,使用了带有预形成的环A,B和D的前体,该环含有共轭的硝酮体系(16/26)。这些是由环己烯酮10 / 20a,b从环状环己烯酮按照略作修改的标准程序分六步制备的。通过迈克尔加成14b的烯醇化物未能获得末端甲硅烷基炔烃15b在强Si-O络合的基础上解释了对硝基苯乙烯的苯胺。用空间上要求更高的三异丙基甲硅烷基取代三甲基甲硅烷基取代基后,按预期完成了15c的形成。在对硝基化合物16/26进行热诱导的1,7-环化后,主要的环烯基中间体发生了多步重排,从而形成了相应的6,6,6,5-和6,6,5,5-环类固醇(17/27和18/28),产率为55-86%。