CARBOHYDRATES IN THE SYNTHESIS OF TUMOR-A SSOCIATED ANTIGENS - SYNTHESIS OF LEWIS-Y DETERMINANTS

The synthesis of the ethoxycarbonyloctanyl glycoside of the Lewis-Y (L e(y)) tetrasaccharide, a part of complex glycosphingolipids, was based on the trichloroacetimidate method for glycoside synthesis. The regio selective introduction of protective groups and the high yield of epim ers of the azidonitration reaction applied to methyl-2-butyl)silyl]-be ta-D-galactopyr-anosyl}-(1 --> 2,3-dimethyl-2-butyl)silyl]-D-arabino-h ex-1-enitol led to a lactosamine acceptor molecule. The double specifi c introduction of an alpha-L-fucosyl group in high yield gave a protec ted Le(y)-tetrasaccharide. After activation to give the alpha-trichlor oacetimidate, specific beta-glycosylation with 8-ethoxycarbonyl octano l under S(N) 2 condition, followed by cleavage of all protective group s 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 y ield.