Stereoselective syntheses of O- and S-nitrophenyl glycosides. Part III. Syntheses in the α- D -galactopyranose and α-maltose series

The action of p-nitrophenol on penta-O-acetyl-β-D-galactopyranose in dichloromethane, in the presence of stannic tetrachloride, gave p-nitrophenyl α-D-galactoside in fair yield. This technique failed when o-nitrophenol was used. Tetra-O-acetyl-β-D-galactopyranosyl and hepta-O-acetyl-β-maltosyl chlorides were converted to p- or o-nitrophenyl α-D-glycosides and p-nitrophenyl α-D-1-thioglycosides in good yield using hexamethylphosphoramide as a solvent and the sodium salt of the phenols as nucleophiles. The galactosides have been functionalized for further condensation at the C-4 position by selective benzoylation.