Stereoselective process for the production of protected 2 ', 2'-difluoro lactones

摘要

The present invention provides a process for preparing lactone intermediates to 2 min ,2 min -difluoronucleosides whereby reversion back to the lactone's open chain precursor is minimized and the desired erythro enantiomer can be selectively isolated from an enantiomeric mixture of erythro and threo lactones in crystalline form. Also provided is a process for producing 2 min -deoxy-2 min ,2 min -difluoronucleosides in about a 1:1 alpha / beta anomeric ratio, and processes for selectively isolating beta -2 min -deoxy-2 min ,2 min -difluorocytidine, or an organic or inorganic acid addition salt thereof, from the 1:1 alpha / beta mixture.