Chemoenzymic synthesis of sialylated and fucosylated oligosaccharides having an N-acetyllactosaminyl core

Several sialylated and fucosylated oligosaccharides, based upon the N-acetyllactosaminyl core structure, have been synthesized from a single trisaccharide glycoside, β- d-GlcNAc-(1 → 3)-β- d-Gal-(1 → 4)-β- d-GlcNAc-OCH 2(CH 2) 7CO 2CH 3, by the sequential use of several glycosyltransferases and one sialidase. In these chemoenzymic syntheses, selective internal monofucosylation of a dimeric N-acetyl-lactosaminyl tetrasaccharide is achieved via two routes. It is demonstrated that the pentasaccharide β- d-Gal-(1 → 4)-β- d-GlcNAc-(1 → 3)-β- d-Gal-(1 → 4)-[α- l-Fuc-(1 → 3)]-β- d-GlcNAc-OCH 2 (CH 2) 7 − CO 2CH 3 is an acceptor for the rat liver β- d-Gal-(1 → 3 4 )- d-GlcNAc α2,3- and β- d-Gal-(1 → 4)- d-GlcNAc α2,6-sialyltransferases. Among the structures obtained is the terminal hexasaccharide of the CD-65/VIM-2 epitope.