Prepn. of apovincaminic acid ester(s) - by azeotropic dehydration of vincamic or epi-vincaminic acid ester(s); useful at hypotensives and vasodilators

摘要

Prepn. of (+)- or (2)-apovincamic acid esters of formula (I) is carried out by dehydrating a (+)- or (-)-vincamic acid ester of formula (II) or a (+)- or (-)-epivincamic acid ester of formula (III); (where R is 2-6C alkyl). Dehydration is effected in a water-immiscible solvent which forms an azeotropic mixt. with H2O, in the presence of a strong organic acid which as a dissociation constant of >=10-2, does not conform an azeotropic mixt. with H2O and has a low vapour pressure at the reaction temp. The H2O formed in the reaction is continuously removed by azeotropic distn. Cpds. (I) are useful as hypotensives and vasodilators. The process gives practically quantitative yields of high-purity (I) free of (II) or (III).