2,3′-Difluoro-and 3′-Azido-2′-Fluoro Substituted Dideoxypyrimidines as Potential Anti-HIV Agents

2′-Deoxy-2′-fluorouridine (2) was obtained by reaction of the arabinofuranosyl nucleoside 1 with diethylaminosulfur trifluoride followed by detritylation. After inversion of the configuration at the 3′-position, 4 was used as starting material for the preparation of the 2′,3′-disubstituted derivatives 6, 7, 8 and 10.