Regioselective synthesis of 6-S-alkyl and 6-S-glycosyl-6-thio-d-mannofuranose derivatives from 5,6-O-cyclic sulfate precursors

C-6 opening of 5,6-cyclic sulfate derivatives of mannofuranose with a thiolate anion followed by acidic hydrolysis of the acyclic sulfate gave 6-S-alkyl derivatives in good yields (70–95%) and short reaction times (10–15 min). This methodology was applied to the synthesis of methyl 2,3-O-isopropylidene-6-S-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-6-thio-α-d-mannofuranoside (70%), 2,3-O-isopropylidene-6-S-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)-6-thio-α-d-mannofuranose (87%) and 2,3-O-isopropylidene-6-S-(1,2:3,4-di-O-isopropylidene-α-d-galactopyranos-6-yl)-6-thio-α-d-mannofuranose (87%).