Coupling reactions were performed in the α-D-glucopyranosyl bromide series (i.e. compounds 1 a–c, 2 a, b, 3 and 4 ) and the α-D-mannopyranosyl bromide series (i.e. compounds 7 a–c, 8 a, b, 9 ) with aglycons 5 or 10 in the presence of insoluble silver salt promotors. (i.e. silver silicate and silver zeolite). The insoluble silver salt promotes the formation of the β-glycosidic linkage, while a non-participating group is present at C-2 of the glycon. It was found that in both series 4-O-acyl functions increase the β/α ratio of the glycosidic bond formation relative to 4-O-alkyl functions, whereas 3-O and 6-O-acyl functions decrease this ratio. We assume that inductive effects are responsible for the influence exerted by 3-O-substituents, but that through-bond interactions are essential for the effects exerted by 4-O and 6-O substituents. Another unexpected finding was that coupling of α-D-mannopyranosyl bromide derivatives gave much higher β/α ratios than the corresponding reactions of α -D-glucopyranosyl bromides.