alkaloids is described using stereoselective dipolar cycloaddition reactions of azomethine ylides. The ylides were derived from N-protected 2-butenylindole-3-carbaldehydes, which were prepared in three steps from 2-methylindole. Condensation of these aldehydes with a variety of alkylamino esters or amino acids or with N-methylhydroxylamine gave the required azomethine ylides or nitrone that undergo intramolecular
使用偶氮甲碱叶立德的立体选择性偶极环加成反应描述了在许多
吲哚生物碱中发现的四环系统的四步路线。叶立德衍生自 N-保护的
2-丁烯基
吲哚-3-
甲醛,其由
2-甲基吲哚分三步制备。这些醛与各种烷基
氨基酯或
氨基酸或与 N-甲基
羟胺的缩合得到所需的偶氮甲碱叶立德或硝酮,它们在未活化的侧链烯烃上发生分子内环加成反应。环加成立体选择性地建立了两个新环和多达三个新的立体中心。在与
N-烯丙基甘氨酸环加成后,N-脱烯丙基化提供 N-未取代的产物,这构成了
生物碱脱乙基叶酸的正式合成。