Glycosylation of lactose: synthesis of branched oligosaccharides involved in the biosynthesis of glycolipids having blood-group I activity.

Methyl 4-O-(2-O-benzoyl-4,6-O-benzylidene-beta-D-galactopyranosyl)-2,3, 6-tri-O-benzoyl-beta-D-glucopyranoside (2) was prepared in four steps from methyl beta-lactoside. Crystalline 2 was a convenient substrate for the synthesis of branched oligosaccharides derived from lactose. High-yield glycosylations were performed first at the 3'-position and then, after removal of the benzylidene group, at the 6'-position, using trichloroacetimidates of N-phthaloylamino sugars.

Biosynthesis of blood group I antigens. Identification of a UDP-GlcNAc:GlcNAc beta 1-3Gal(-R) beta 1-6(GlcNAc to Gal) N-acetylglucosaminyltransferase in hog gastric mucosa.

A beta 1-6N-acetylglucosaminyltransferase has been identified in microsomal preparations from hog gastric mucosa which is able to synthesize branch points in branched lactosaminoglycans (blood group I antigenic structures). The enzyme can be assayed specifically using the synthetic trisaccharide GlcNAc beta 1-3Gal beta 1-4Glc beta-OMe as acceptor. The product of the transferase reaction was isolated and identified by methylation analysis as, (Formula: see text) Into this tetrasaccharide two galactose residues were incorporated by the specific beta-N-acetylglucosaminide beta 1-4-galactosyltransferase from bovine milk.