Synthesis of 2',3'-Dideoxy-2'-trifluoromethyl-N-azanucleosides

The trifluoromethylation of (Z)/(E)-tert-butyl (4S)-4-(2'-ethoxycarbonyl-2'-bromoprop-1'-enyl)-2,2-dimethyloxazolidine-3-carboxylate (4), which is derived from chiral serine aldehyde, yields α-trifluoromethyl-α,β-unsaturated ester 1. Compound 1 is used as a key intermediate for the synthesis of a number of 2',3'-dideoxy-2'-trifluoromethyl-N-azanucleosides.