New derivatives of reducing oligosaccharides and their use in enzymatic reactions: efficient synthesis of sialyl Lewis a and sialyl dimeric Lewis x glycoconjugates

The reducing oligosaccharides lactose and lacto-N-tetraose were reductively aminated with benzyloxycarbonylaminoaniline and sodium cyanoborohydride, f ollowed by treatment of the resulting secondary amines with acetic anhydrid e. The resulting N-acetyl-N-(4-benzyroxycarbonylaminophenyl)-1-amino-1-deox yalditol oligosaccharide derivatives were subjected to stepwise enzymatic e longation with various glycosyltransferases/nucleotide sugars. Purification of the products after each enzymatic step was conveniently performed by so lid-phase extraction on silica gel C-ls cartridges. Two oligosaccharide der ivatives (with sialyl Lewis a and sialyl dimeric Lewis x structures) were p repared. Conversion of the obtained derivatives into neoglycoproteins by th e sequence hydrogenolysis, thiophosgene treatment, and protein coupling was carried out. (C) 2000 Elsevier Science Ltd. All rights reserved.