A METHOD OF PREPARING THE SCOPINE ESTER OF DI-(2-THIENYL)GLYCOLIC ACID, AN INTERMEDIATE IN THE SYNTHESIS OF TIOTROPIUM BROMIDE

摘要

The present invention relates to a preparation method of tiotropium bromide of formula II, comprising the following steps: a) preparation of the scopine ester of formula I by transesterification of methyl di(2thienyl)glycolate of formula IV with scopine of formula III in the presence of a substoichiometric amount of a sterically hindered base selected from the group of alkali salts of branched C3 to C5 alkoxides in an inert solvent, b) isolation of the scopine ester of formula I, and c) quaternization of the scopine ester of formula I with methyl bromide.