Substituent effects in carbohydrate chemistry, Part II+. Coupling reactions involving gluco‐ and galacto‐pyranosyl bromides promoted by insoluble silver salts

Coupling reactions have been conducted between α-D-glyco- and galacto-pyranosyl bromide derivatives and 3-O-acetyl-1,6-anhydro-2-azido-2-deoxy-β-D-glucopyranose in the presence of insoluble silver salt promoters. It was found that 4-O-acyl functions increase the β/α ratio of the disaccharide formation relative to 4-O-alkyl functions, whereas 3-O- and 6-O-acyl functions decrease this ratio. It was also found that coupling of α-D-galactopyranosyl bromide derivatives gave much higher β/α ratios than did reactions with the corresponding α-D-glucopyranosyl bromides.