Enzymes as Tools for Glycopeptide Synthesis

The high specificity and stereoselectivity of enzymes, as well as the mild conditions under which they react, make enzyme-catalyzed reactions versatile tools in the synthesis of glycoconjugates. In some instances, an enzymic one-step transformation affords higher yields then the conventional and more-complex chemical synthesis. The application of enzymes in glycopeptide synthesis is under active development for selective deprotection and glycosylation purposes. 

Transfer of glycosyl residues to saccahride acceptors under catalysis by glycosyltransferases has been studied in recent years (85,88,89). In contrast to chemical glycosylation, enzymic extensions of the saccharide chain of 

Enzymic synthesis of the trisaccharide asparagine conjugate -d-NeupAc-(2 — 6)-/ -D-Galp-( 1 — 4)-/ -D-GlcpNAc-(l — 4A L-Asn (186) has been reported by Auge and coworkers (91). 

Similarly Thiem and Wiemann (92) conducted the galactosylation of the 2-acetamido-2-deoxy-D-glucose-L-asparagine derivative 183 and the chitobiose-L-asparagine derivative 187 to furnish the di- and trisaccharide derivatives 185 and 188, respectively, by using galactosyltransferase. 

Likewise, the galactosylation of O-glycopeptide derivatives 189-191 to give O-lactosamine - L-serine derivatives (192-194) using (1 - 4)-/ -d- 

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