STEREOSELECTIVE METHOD FOR PRODUCING THE 22R EPIMER OF BUDESONIDE

摘要

The present invention is directed to a stereoselective process for the preparation of the C-22 R epimer of budesonide, having a purity higher than 90%, comprising the following steps: a) stereoselective transketalisation of 9 alpha -bromo-desonide or 9 alpha -iodo-desonide, by reaction with butyraldehyde in the presence of a halohydric acid selected from between aqueous HBr and Hl, to give 9 alpha -bromo-budesonide or 9 alpha -iodo-budesonide; b) treatment of 9 alpha -bromo-budesonide or 9 alpha -iodo-budesonide from step a) with a dehalogenating agent.