Nucleosides thiosugars

Phosphorus dithioacids [RR P(S)SH] are effective sulfur nucleophiles for the synthesis of 3 -S-or 5 -5 -nucleosides [107]. Furthermore, Mitsunobu reactions have also been used to convert primary sugar alcohols into corresponding thiosugar derivatives in one-pot manner [108]. 

The reaction of the bicyclic thiosugar 171 with N6-benzoyladenine in the presence of moist tin(IV) chloride furnishes the ring-rearranged nucleoside product 172 instead of the normal glycosylation product [137]. On heating mesylate 173 under reflux in the presence of a nucleophile, the thermal ring-expanding reaction occurs [138] (O Scheme 41). 

Trifluoromethyl substituted nucleoside 118 was synthesized from a-trifluoromethyl-a,p-unsaturated ester 117 <02JOC1016> in eight steps involving the usual Pummerer rearrangement. Compound 119 was synthesized from L-xylose via 2-deoxy-2-C-difluoromethylene-4-thiosugar... 

The imidazo[l,2-a]pyrid-3-yl acyclo C-nucleoside 209 having a truncated thiosugar residue was synthesized and found to be markedly active against varicella zoster virus (94MI1). 

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