SYNTHESIS OF 2-ALKYLTHIO ANALOGS OF AZT AND THEIR ACTIVITY AGAINST HIV-1

S-2-Alkylated 3'-azido-2',3'-dideoxy-2-thiouridines (5) and their corr esponding a anomers have been synthesized through two routes: 1) by co ndensation of silylated 2-alkylthiopyridin-4(1H)-ones (2) with methyl 3-azido-5-O-(tert-butyldiphenylsilyl)-2,3-dideoxy- alpha,beta-D-erythr o-pentofuranoside (3); 2) by condensation with methyl -dideoxy-3-iodo- alpha,beta-D-threo-pentofuranoside (7), followed by reaction of the ob tained iodonucleoside (8) with sodium azide to give the protected azid onucleoside (10) and the 3',4'-didehydro-2',3'-dideoxy nucleoside (11) .