BUILDING UNITS OF OLIGOSACCHARIDES .102. SYNTHESIS OF MODIFIED DERIVATIVES OF 2-ACETAMIDO-2-DEOXY-D-GALACTOSE FOR THE EXAMINATION OF SUBSTRATE SPECIFICITIES OF CORE 1-BETA-3-GAL-TRANSFERASE AND CORE 3-BETA-3-GLCNAC-TRANSFERASE INVOLVED IN THE BIOSYNTHESIS OF O-GLYCOPROTEINS

The 2-, 3-, 4-, and 6-deoxy derivatives of benzyl 2-acetamido-2-deoxy-alpha-D-galactopyranoside (7) have been synthesized to test substrate specificities of glycosyltransferases involved in the biosynthesis of O-glycoproteins. The core 1-beta-3-Gal-transferase does not require the 6-hydroxyl group for activity in contrast to the glycosylation reaction of the core 3-beta-GlcNAc-transferase which requires the 6-hydroxyl group. Compounds with reactive groups substituting the 6-hydroxyl group such as the diazirine 45 could be suitable for photolabeling of the former enzyme. A column for affinity chromatography with the 6-deoxy derivative as the ligand could be useful to separate the two enzymes during purification.