LIGAND RECOGNITION BY E-SELECTIN - SYNTHESIS, INHIBITORY ACTIVITY, AND CONFORMATIONAL-ANALYSIS OF BIVALENT SIALYL-LEWIS-X ANALOGS

Several sialyl Lewis x dimers anchored onto a galactose template or attached to 1,4-butanediol or 1,5-pentanediol have been prepared chemoenzymatically and evaluated as inhibitors of E-selectin-mediated cell adhesion. Two monosaccharide units were simultaneously incorporated (i.e., Gal, NeuAc, Fuc) by a glycosyltransferase into a chemically synthesized core structure containing GlcNAc and Gal. Each of the galactose-anchored dimers had higher activity than the sialyl Lewis x pentasaccharide la, with the general trend being 3,6-linked > 2,3 greater than or equal to 4,6 greater than or equal to 2,6 monomer. The dimers linked to butanediol or pentanediol showed the same level of activity as the pentasaccharide monomer. Conformational analysis of these dimers with NMR indicated that each sialyl Lewis x domain of the dimers retains the same conformation as the monomer. The differences in activity of the dimers most likely derive from differences in the relative orientation and distance between the monomer domains, suggesting the importance of the linker used in the preparation of dimers.