A HIGHLY CONVERGENT TOTAL SYNTHETIC ROUTE TO GLYCOPEPTIDES CARRYING AHIGH-MANNOSE CORE PENTASACCHARIDE DOMAIN N-LINKED TO A NATURAL PEPTIDE MOTIF

N-Linked glycopeptides were synthesized by condensation of a high-mann ose anomeric amine bearing a pentasaccharide with aspartic-acid-contai ning tri-and pentapeptides through the agency of IIDQ. The pentasaccha ride portion, corresponding to the ''core'' region of all asparagine-l inked glycoproteins, was assembled by means of glycal-derived thioethy l donors and glycal accepters. The central mannose residue was establi shed by inversion of the C 2 hydroxyl of a glucosyl precursor in the p entasaccharide, The protecting-group scheme employed allows the extens ion of the pentasaccharide through the terminal mannose units. While a fully convergent coupling of the high-mannose carbohydrate to the pep tide domain has thus been accomplished for the first time with a fully synthetic sugar, the stereochemical integrity of the anomeric center of the carbohydrate domain was not maintained and a mixture of glycope ptides was obtained.