Enzymic transfer of 6-modified d-galactosyl residues: synthesis of biantennary penta- and hepta-saccharides having two 6-deoxy-d-galactose residues at the nonreducing end and evaluation of 6-deoxy-d-galactosyl transfer to glycoprotein using bovine β-(1 →

UDP-6-Deoxy-d-galactose and UDP-6-deoxy-6-fluoro-d-galactose were synthesized and their transfer to 2-acetamido-2-deoxy-d-glucose (N-acetyl-d-glucosamine) by β-(1 → 4)-galactosyltransferase was examined. The transfer rates of 6-deoxy-d-galactose and 6-deoxy-6-fluoro-d-galactose were 1.3 and 0.2% of that of d-galactosyl transfer, respectively. The 2-acetamido-4-O-(6-deoxy-β-d-galactopyranosyl)-2-deoxy-d-glucopyranose (6′-deoxy-N-acetyllactosamine) and methyl 2-acetamido-4-O-(6-deoxy-6-fluoro-β-d-galactopyranosyl)-2-deoxy-d-glucopyranoside (6′-deoxy-6′-fluoro-N-acetyllactosamine) were synthesized enzymatically in 30 and 59% yields, respectively. Further, 6-deoxy-d-galactose could be completely transferred to N-linked type biantennary oligosaccharides having two N-acetyl-d-glucosaminyl residues at the nonreducing end to give the corresponding penta- and hepta-saccharides in 55 and 57% yields, respectively. An assay of 6-deoxy-d-galactosyl transfer using asialo agalacto α1-acid glycoprotein as an acceptor suggested that 6-deoxy-d-galactose was transferred to about 30% of the N-acetyl-d-glucosaminyl residues in the N-linked oligosaccharides of the glycoprotein.