Artificial glycopolypeptide conjugates: Simple synthesis of lactose- and N,N'-diacetylchitobiose-substituted poly(L-glutamic acid)s through N-beta-glycoside linkages and their interaction with lectins

Poly(glutamic acid)s carrying lactose-and N,N'-diacetylchitobiose residues were synthesized via a simple two-step procedure. The oligosaccharides were treated with ammonium hydrogen carbonate and the resulting N-beta-glycosylamine was coupled with pendant carboxyl groups of poly(L-glutamic acid) in the presence of a mixture of benzotriazol-1-yl-oxy-tris(dimethylamino)phosphonium hexafluorophosphate (BOP) and 1-hydroxybenzotriazole (HOBt) in dimethyl sulfoxide. The oligosaccharide incorporated as pendant N-glycosides was estimated by H-1-NMR spectroscopy to be 30 mol% (or 45 wt%) for lactose and 27 mol% (46 wt%) for chitobiose. The glycopolypeptide carrying N,N'-diacetyl-chitobiose inhibited hemagglutination activity of wheat germ agglutinin (WGA) much more strongly (about 10(6) times) than N,N'-diacetylchitobiose itself, The high activity is due to the cluster or high density effect of the glycopolypeptides.