Chromatographic separation of Lewis a and Lewis x oligosaccharides as glycosynthons

Lewis a and Lewis x oligosaccharides Galbeta3(Fucalpha4)GlcNAcbeta3Galbeta4Glc and Galbeta4(Fucalpha3)GlcNAcbeta3Galbeta4Glc are easily isolated as a mixture from biological fluids, including human milk. However, because they behave almost identically in most chromatographic systems, it is difficult to have each of them as a pure compound. Incidentally, we found that they were easily separated by HPLC as glycosynthons [Galbeta3(Fucalpha4)GlcNAcbeta3Galbeta4Glc-Glp-betaAla-OBzl and Galbeta4(Fucalpha3)GlcNAcbeta3Galbeta4Glc-Glp-betaAla-OBzl] after substitution of the terminal reducing sugar by a short peptide (pyroglutamyl-betaalanyl-O-benzyl ester) in a one-pot two-step reaction (Carbohydr. Lett. 1 (1995) 269; Bioconjug. Chem. 9 (1998) 268). Such glycosynthons are easily either converted back to native Lewis a and Lewis x oligosaccharides upon hydrazinolysis or used to synthesize glycoconjugates, such as glycoclusters, glycopeptides, glycooligonucleotides, glycosylated polymers or glycosylated matrices for therapeutic or analytical purposes. (C) 2003 Editions scientifiques et medicales Elsevier SAS and Societe francaise de biochimie et biologic moleculaire. All rights reserved.