Regioselective Synthesis of β-D-Gal-(1→3)-D-Glcnac Using β-Galactosidase from Xanthomonas Manihotis

Abstract

The carbohydrate chains of glycoconjugates are involved in a variety of molecular recognition events. For example, the tetrasaccharide sialyl Lewis a (sLe^a) plays a pivotal role in the metastasis of cancer cells.¹ In order to elucidate the biological tunction of carbohydrate chains, many researchers have synthesized components of carbohydrate chains. 2-Acetamido-2-deoxy-3-O-(β-D-galactopyranosyl)-D-glucopyranose (1) is an important constituent of sLe^a in complex type carbohydrate chains. This disaccharide has been synthesized using the transglycosylation activity of bovine testes β-galactosidase.² In this case the product mixtures contained unwanted isomers and had to be treated with Escherichia coli β-galactosidase in order to hydrolyze the undesired isomers. Eventually, 1 was obtained in 12 % yield. This methods is far from ideal as it requies two steps to obtain 1 and bovine testes are expensive and not easily available.