[Carbohydrate building blocks for the construction of tumor-associated antigens. Synthesis of Lewis Y determinants].

The synthesis of the ethoxycarbonyloctanyl glycoside of the Lewis-Y (Ley) 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-O-[dimethyl-(2,3-dimethyl-2-butyl)silyl]-beta-D- galactopyranosyl]-(1-->4)-3-O-acetyl-1,5-anhydro-6-O-[dimet hyl-(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 Ley-tetrasaccharide. After activation to give the alpha-trichloroacetimidate, specific beta-glycosylation with 8-ethoxycarbonyl octanol under SN 2 condition, followed by cleavage of all protective groups led to the tetrasaccharide, alpha-L-Fucp-(1-->2)-beta-D-galp-(1-->4)-[alpha-L-fucp-(1--> 3)]-beta-D- GlcpNAcO(CH2)8CO2Et in high yield.