[structure: see text]. A novel formal synthesis of cephalotaxine (CET), the parent structure of the antileukemia Cephalotaxus alkaloids, was achieved via a facile Friedel-Crafts cyclization of the amino (or amido) spiro-cyclopentenone precursor (A) mediated by a protic acid leading to tetracyclic ketone B. A remarkable stereoelectronic effect of the methylenedioxy substituent (R) and an interesting
[结构:见文字]。一种新的形式的头孢他辛(CET),即抗白血病头足类
生物碱的母体结构,是通过质子酸介导的
氨基(或酰胺基)螺-
环戊烯酮前体(A)的简便Friedel-Crafts环化反应而实现的观察到了亚甲二氧基取代基(R)的显着立体电子效应和CET核心环系统的有趣骨架异构化(B,X = H2)。