Synthesis of glycopeptides from the carbohydrate-protein linkage region of proteoglycans.

2,3,4,6-Tetra-O-benzoyl-alpha-D-galactoyranosyl trichloroacetimidate was condensed with benzyl 2,3-O-isopropylidene-beta-D-xylopyranoside to give the corresponding beta-(1----4)-linked disaccharide derivative, which was transformed into 2,3-di-O-benzoyl-4-O-(2,3,4,6-tetra-O-benzoyl-beta-D-galactopyranosyl)- alpha-D-xylopyranosyl trichloroacetimidate. This glycosyl donor was condensed with a set of selectively C,N-protected L-seryl-glycine dipeptide units. Selective deblocking at the C- or N-termini of the glycosylated or non-glycosylated dipeptide segments, and coupling using the mixed-anhydride procedure allowed the construction in high yield of partially or fully glycosylated oligopeptides from the carbohydrate-protein linkage region of proteoglycan.