Cinchona alkaloid derivatives, their process of preparation and their use as catalysts

摘要

The present invention provides a process for preparing a substantially stereochemically pure compound of formula (I), or a salt thereof wherein R 1 and R 2 are independently selected from the group consisting of H, -CH 2 -CH 3 , and -CH=CH 2 , the process comprising the step of demethylating the corresponding methylated compound of formula (II) in the presence of an alkaline or alkaline earth metal (C 1 -C 10 ) alkylthiolate salt and a polar aprotic solvent.