CHEMOENZYMIC SYNTHESIS OF SIALYLATED AND FUCOSYLATED OLIGOSACCHARIDESHAVING AN N-ACETYLLACTOSAMINYL CORE

Several sialylated and fucosylated oligosaccharides, based upon the N- acetyllactosaminyl core structure, have been synthesized from a single trisaccharide glycoside, beta-D-GlcNAc-(1 --> 3)-beta-D-Gal-(1 --> 4) -beta-D-GlcNAc-OCH2(CH2)(7)CO2CH3, by the sequential use of several gl ycosyltransferases and one sialidase. In these chemoenzymic syntheses, selective internal monofucosylation of a dimeric N-acetyllactosaminyl tetrasaccharide is achieved via two routes. It is demonstrated that t he pentasaccharide beta-D-Gal-(1 --> 4)-beta-D-GlcNAc-(1 --> 3)-P-D-Ga l-(1 --> 4)-[alpha-L-Fuc-(1 --> 3)]-beta-D-GlcNAc-OCH2(CH2)(7)-CO2CH3 is an acceptor for the rat liver beta-D-Gal-(1 --> 3/4)-D-GlcNAc alpha 2,3- and beta-D-Gal-(1 --> 4)-D-GlcNAc alpha 2,6-sialyltransferases. Among the structures obtained is the terminal hexasaccharide of the CD -65/VIM-2 epitope.