A convenient method for S-glycosidic bond formation. Synthesis of p-lodophenyl 4′-thiomaltotrioside and its 2″,3″-unsaturated analogue

Abstract

The axial trifluoromethanesulphonate group at C-4′ of acylated galactopyranosylglucopyranoside (11) was substituted by sulphur nucleophiles: selective S-deacetylation and activation of peracetylated 1-thio-α-D-glucose (12) led to p-iodophenyl 4′-thiomaltotrioside derivative (13); substitution by potassium thioacetate and S-deacetylation afforded 4′-thiomaltoside (17) which gave, by condensation with acetylated 1,5-anhydro-2-deoxy-D-arabino-hex-1-enitol, under acidic conditions, as a major product the 2″,3″-unsaturated trisaccharide (19). The synthesis of compound (2), the sulphur positional isomer of (1), in 73% yield is also reported.