Enzymic synthesis of HexNAc-containing disaccharide glycosides.

The following disaccharide glycosides were obtained from the appropriate donor and acceptor glycosides by employing glycosidases from the mollusc Chamelea gallina as catalysts: alpha-D-Galp-OMe (N-acetyl-alpha-D- galactosaminidase), beta-D-GalpNAc-(1----3)-beta-D-Galp-OMe, beta-D-GlcpNAc-(1----3)-beta-D-Galp-OMe, and beta-D-GlcpNAc-(1----6)-alpha-D-Manp-OMe (N-acetyl-beta-D-hexosaminidase). The regioselectivity of the N-acetyl-beta-D-hexosaminidase-catalysed reactions depended on the anomeric configuration of the acceptor. Thus, alpha-D-Galp-OMe gave beta-D-GlcpNAc- (1----6)-alpha-D-Galp-OMe almost exclusively, whereas beta-D-Galp-OMe gave beta-D-GlcpNAc-(1----3)-beta-D-Galp-OMe and beta-D-GlcpNAc-(1----6)-beta-D-Galp-OMe in almost equal amounts. The isolation of the products by chromatography was straightforward.