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

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