3, 6-Dioxa-octylene 1, 8-di-O-{4-O-[(3-O-α-D- galactopyranosyl)-β- D-galactopyranosyl]-2-deoxy-2-acetamino- β-D-glucopyranoside}(1), useful in the research of hyperacute rejection of xenotransplantation, was synthesized for the first time. Trichloroacetimidate method was successfully applied to obtain the trisaccharide PEG dimer or PEG glycoside respectively under different glycosylation conditions.

Key words: PYRANOSE, GALACTOSE, PYRANE P, GRAFT REJECTION, OLIGOSACCHARIDE, DIMERS, IMIDE, TRICHLOROACETIC ACID P, GLYCOSIDE, SYNTHESIS