Synthesis of glycopeptides of the mucin type containing a β- d-Glc pNAc-(1→3)- d-Gal pNAc unit

Abstract

Mucin-type O-glycopeptides containing the β- d-Glc pNAc-(1→3)- d-Gal pNAc core unit were synthesised from 2-azido-2-deoxy- d-glucose, 2-azido-2-deoxy- d-galactose, 2-azido-2-deoxylactose, and l-serine precursors, using the trichloroacetimidate method. Thus, β- d-Glc pNAc-(1→3)-α- d-Gal pNAc-(1→3)-Ser ( 1) and a derivative of β- d-Gal p-(1→4)-β- d-Glc pNAc-(1→6)-[β- d-Glc pNAc-(1→3)]-α- d-Gal pNAc-(1→3)-Ser ( 2) were obtained. A precursor of 1 having HO-4,6 of the 2-azido-2-deoxy- d-galactose residue unsubstituted was a valuable intermediate for the synthesis of 2 due to regioselective glycosylation at O-6. Regioselectivity in this reaction was not observed for precursors having a tert-butyldimethylsilyl group at O-1 instead of a protected l-serine moiety.