摘要:
The synthesis of the ethoxycarbonyloctanyl glycoside of the Lewis-Y (Le(y)) tetrasaccharide, a part of complex glycosphingolipids, was based on the trichloroacetimidate method for glycoside synthesis. The regioselective introduction of protective groups and the high yield of epimers of the azidonitration reaction applied to O-(2,3,4-tri-O-acetyl-6-0-[dimethyl-(2,3-dimethyl-2-butyl)silyl]-beta-D-galactopyr-anosyl}-(1 --> 4)-3-0-acetyl-1,5-anhydro-6-0-[dimethyl-(2,3-dimethyl-2-butyl)silyl]-D-arabino-hex-1-enitol led to a lactosamine acceptor molecule. The double specific introduction of an alpha-L-fucosyl group in high yield gave a protected Le(y)-tetrasaccharide. After activation to give the alpha-trichloroacetimidate, specific beta-glycosylation with 8-ethoxycarbonyl octanol under S(N) 2 condition, followed by cleavage of all protective groups led to the tetrasaccharide, alpha-L-Fuc p-(l --> 2)-beta-D-Gal p-(1 --> 4)-[alpha-L-Fuc p-(l --> 3)]-beta-D-Glc pNAcO(CH2)8CO2Et in high yield.