ABSTRACT
P-L-FD4C (5.4),5 the benzimidazole-P-L-riboside (5.5),6 and the 2 \2 ’-difluoro-Lnucleoside (5.6)7
O f the four possible stereoisomers of 2 \3 ’-dideoxy-3’-thiacytidine, (-)-P-L-(2i?, 55)- 1,3-oxathiolanylcytosine (3TC, 5.1) was found to be the most potent against HIV and HBV with the least toxic effects.8 The asymmetric synthesis of the key L-oxathiolane (5.13) was achieved from L-gulose (5.7) via the 1,6-thioanhydro-Lgulopyranose intermediate (5.10) (Scheme 5.1).9
