Process for the preparation of esters-14,15-dihydro-14 b hydroxy- (3x 16x) -eburnamenina-14-carboxylic

摘要

Esters of 14,15-dihydro 146-hydroxy (3a,16a)-eburnamenine 14-carboxylic acid, of formula (I), in which R is alkyl, methyl, ethyl or other, are made by (a) reacting the potassium salt of the acid with an alkyl bromide in a phase transference reaction in presence of a catalyst e.g. tetrabutyl ammonium bromide, in a mixt. of water, benzene and/or toluene, at between 20 deg.C and b.pt., for 3-24 hours; (b) concentrating the organic phase and recrystallising it from an organic solvent.