COMBINED CHEMICAL ENZYMATIC-SYNTHESIS OF DEOXYGENATED OLIGOSACCHARIDE ANALOGS - TRANSFER OF DEOXYGENATED D-GLCPNAC RESIDUES FROM THEIR UDP-GLCPNAC DERIVATIVES USING N-ACETYLGLUCOSAMINYLTRANSFERASE-I

The 3″-, 4″-, and 6″-deoxy analogs of UDP-GlcpNAc have been synthesized chemically and found to act as donor-substrates for N-acetylglucosaminyltransferase-I (GnT-I) from human milk. Incubation of UDP-GlcpNAc and these deoxy analogs with GnT-I in the presence of α-d-Manp-(1→3)-[α-d-Manp-(1→6)]-β-d-Manp-O(CH2)8COOMe gave β-d-GlcpNAc-(1→2)-α-d-Manp-(1→3)-[α-d-Manp-(1→6)]-β-d-Manp-O(CH2)8COOMe(6), and the deoxy analogs 12-14 where HO-3, HO-4, and HO-6, respectively, of the β-d-GlcNAc residue were replaced by hydrogen. The tetrasaccharide glycosides 6 and 12-14 were characterized by 1H-n.m.r. spectroscopy and evaluated as acceptors for GnT-II, the next enzyme in the pathway of biosynthesis of Asn-linked oligosaccharides. Deoxygenation of the 3-position of the β-d-GlcNAc residue of 6 completely abolished its acceptor activity, whereas removal of HO-4 or HO-6 caused only modest decreases in activity. © 1990.