Synthesis and glycosaminoglycan priming activity of three disaccharides related to the linkage region tetrasaccharide of proteoglycans

To test if disaccharides might serve as primers of oligosaccharide synthesis in animal cells, we synthesized 2-naphthyl O-(β-d-galactopyranosyl)-(1 → 4)-β-d-xylopyranoside, 2-naphthyl O-(β-d-galactopyranosyl)-(1 → 3)-β-d-galactopyranoside, and 2-naphthyl O-(β-d-glucopyranosyluronic acid)-(1 → 3)-β-d-galactopyranoside. These three disaccharides are related to subunits of the linkage tetrasaccharide of heparan sulfate and chondroitin sulfate chains in animal cell proteoglycans. The disaccharides were synthesized with coupling efficiencies of 40–70% using thioglycosides or by activating the monosaccharides with trichloroacetimidate. The structures of these compounds were confirmed by 1H NMR, 13C NMR and elemental analysis. The ability of these disaccharides to prime glycosaminoglycan chains was examined in a Chinese hamster ovary cell mutant, pgsA 745, which lacks xylosyltransferase. The missing enzyme renders the cells dependent on exogenous primers for making glycosaminoglycan chains. 2-Naphthyl O-(β-d-galactopyranosyl)-(1 → 3)-β-d-galactopyranoside and 2-naphthyl O-(β-d-glucopyranosyluronic acid)-(1 → 3)-β-d-galactopyranoside did not stimulate glycosaminoglycan synthesis, but 2-naphthyl O-(β-d-galactopyranosyl)-(1 → 4)-β-d-xylopyranoside at high concentration primed chains. The peracetylated derivative (2-naphthyl O-(2,3,4,6-tetra-O-acetyl-β-d-galactopyranosyl)-(1 → 4)-2,3-di-O-acetyl-β-d-xylopyranoside) primed chains at lower concentration (100 μM), suggesting that cells took up the compound and removed the acetyl groups apparently in the compartment where glycosaminoglycan synthesis occurs.