Preparation of oligosaccharide units library and its utilization.

There is high current interest in developing synthetic routes to oligosaccharides involved in glycoconjugates. Significant attention has been focused on the application of glycosidase-catalyzed transglycosylation for practical synthesis of oligosaccharides. The enzymatic synthesis has become more practical by the use of several glycosidases available in sufficient quantities. This review describes convenient syntheses of di- and trisaccharide units, which are related to molecular recognition, by using regioselective transgalactosylation, trans-N-acetylglucosaminylation, transfucosylation, and transmannosylation. The regioselectivity could be controlled to some extent by using the following techniques: (1) varying enzymes, (2) organic co-solvent system, (3) the configuration of the existing glycosidic linkage of the acceptor and (4) inclusion complex of acceptor glycoside with cyclodextrin. Furthermore, glycopolymers carrying a series of disaccharides containing beta-D-galactosyl residues were synthesized and used as a model in oligosaccharide-lectin interaction analysis. These water-soluble glycopolymers were shown to be useful as probes of carbohydrate recognition.