A note on the use of porous silver silicates as promoter in carbohydrate coupling reactions

Different insoluble silver salts were used to promote the β-glycosidic bond formation between the aglycon methyl (2,3,4-tri-O-benzyl-α-D-glucopyranosyl bromide) uronate (1) and the aglycon 3-O-acetyl-1,6-anhydro-2-azido-2-deoxy-D-glucopyranose (2). The different promoters have different activity, but do not affect the β/α ratio (β/α = 1.5/1) of this coupling reaction. The most reactive promoter is Ag (I) on silica-alumina with enhanced cation capacity.