Synthesis of 2',3'-dideoxy-3'-C-(hydroxymethyl)-4'-thionucleosides as potential inhibitors of HIV

The synthesis of 2',3'-dideoxy-3'-C-(hydrorymethyl)-4'-thionucleosides is described. For the synthesis of the carbohydrate part, the configuration of the secondary hydroxyl group in (2S,3R)-1-O-(p-bromobenzyl)-3-(2'-propenyl)-1,2,4-butanetriol (1) was inverted using Mitsunobu reaction conditions, after which the primary hydroxyl group in product 2 was regioselectively benzoylated using phase-traasfer catalysis. Oxidative cleavage of the allylic double bond, followed by ring closure and exchange of the p-bromobenzyl protecting group gave the methyl furanoside derivative 5, which was further converted to the corresponding dibenzyl dithioacetal 6