Application of the trichloroacetimidate method to the synthesis of glycopeptides of the mucin type containing a beta-D-Galp-(1----3)-D-GalpNAc unit.

Mucin-type O-glycopeptides containing the beta-D-Galp-(1----3)-D-GalpNAc disaccharide core unit, which is also the T-antigenic determinant, were synthesized from D-galactose, 2-azido-2-deoxy-D-galactose, 2-azido-2-deoxylactose, and L-serine precursors by applying the trichloroacetimidate method. Thus, beta-D-Galp-(1----3)-alpha-D-GalpNAc-(1----3)-Ser (1) and beta-D-Galp-(1----4)-beta-D-GlcpNAac-(1----6)-[beta-D-Galp-(1----3 )]-alpha-D-GalpNAc-(1----3)-Ser (2) were obtained. A protected precursor of 2 having free OH groups at C-4 and C-6 of the inner sugar unit is a valuable intermediate for the synthesis of further O-glycopeptides of this core-unit type.