Neighbouring group participation of C-6 substituents of glucose derivatives on the stereoselectivity of the N-glycosidic linkage of glycopeptides

The first example of a glycopeptide with a direct N-alpha-glycosidic linkag e between the trisaccharide and the amino acid residue was found in the glo merular basement membrane of rats. In connection with the total synthesis o f nephritogenoside, glycosyl azides with different protecting groups and ca rbohydrate chain lengths are synthesized, reduced to the corresponding glyc osyl amines and coupled with Z-Asp-OBzl. Remarkable differences in the alph a:beta ratio of the condensation products are observed, caused by neighbour ing group participation.