Collection of Czechoslovak Chemical Communications - digital archive 

Abstract

The synthesis of (±)-vincamine (I), (±)-16-epi-vincamine (XVIII) and (±)-16-epi-21-epi-vincamine (XVII) from 1-ethyl-2,3,4,6,7,12-hexahydroindolo[2,3-a]quinolizine (IV) and 2-chloroacrylonitrile is described. It is characterized by a novel method of oxidation of the key intermediates, (±)-deoxyvincamine (II) and (±)-16-epi-21-epi-deoxyvincamine (XIII) with oxodiperoxymolybdenum (pyridine) (hexamethylphosphoric triamide). The deoxy derivatives II and XIII were prepared by direct or stepwise acid or alkaline hydrolysis of stereoisomeric (±)-eburnane-16-carbonitriles IX-XII, obtained by reduction of the primary imonium salt V, and subsequent esterification. In some cases, the hydrolysis is accompanied by epimerization at C₍₁₆₎.