Uracil (8) was substituted in a Mannich reaction to give the 5-substituted dialkylamino-methyluracils 11a-f in 65-85% yield. Compounds 11a-f were silylated with hexamethyldisilazane and coupled with 2,3-dideoxy-3-fluoro-D-erythro-pentofuranoside 4 and 3-azido-2,3-dideoxy-D-erythro-pentofuranoside 7 to give the corresponding 3′-fluoro-2′,3′-dideoxynucleosides 13a-f and 3′-azido-2′,3′-dideoxy nucleosides 16d, f, respectively, by using trimethylsilyl trifluoromethanesulfonate as a catalyst. Deprotection of the 5-O-(4-phenylbenzoyl) protected nucleosides 13a-f and 16d, f with saturated methanolic ammonia and separation by chromatography yielded the new derivatives of 2′,3′-dideoxy-3′-fluorouridines 14a-f and 15a-f and 2′,3′-dideoxy-3′-azidouridines 17d, f and 18d, f.