First synthesis of two deoxy Lewis(x) pentaosyl glycosphingolipids.

The Lewis(x)-Lewis(x) interaction has been increasingly studied, using a variety of techniques including nuclear magnetic resonance spectroscopy, mass spectrometry, vesicle adhesion, atomic force microscopy, and surface plasmon resonance spectroscopy. However, the detailed molecular mechanism of these weak, divalent cation dependent interactions remains unclear, and new models are needed to probe the nature of this phenomenon in term of key roles of the different hydroxyl groups on Lewis(x) trisaccharide determinant involved in the Lewis(x)-Lewis(x) interaction. An interesting solution is to synthesize a series of Lewis(x) pentaosyl glycosphingolipid derivatives in which one of the eight hydroxyl groups of Lewis(x) trisaccharide is replaced by a hydrogen atom, and to test the adhesion induced by interaction of these derivatives, in order to gain insight into the functions played by the hydroxyl groups of the Lewis(x) trisaccharide. This article describes the synthesis of 3d-deoxy and 4d-deoxy Lewis(x) pentaosyl glycosphingolipids, to be used for study of the Lewis(x)-Lewis(x) interaction.

Weak calcium-mediated interactions between Lewis X-related trisaccharides studied by NMR measurements of residual dipolar couplings.

The Lewis X (LeX) determinant, a trisaccharide with the carbohydrate sequence Galbeta(1-->4)[Fucalpha(1-->3)]GlcNAcbeta, is believed to be responsible for Ca2+-mediated cell-cell interactions. In partly oriented phases composed of mixtures of penta(ethyleneglycol)monododecyl ether HO(CH2CH2O)5C12H25 and n-hexanol in the presence of Ca2+ ions, the variation of the residual dipolar couplings 1DCH of various CiHi vectors in LeX as a function of the concentration of the trisaccharide demonstrates the existence of very weak LeX-Ca2+-LeX complexes in solution. Synthetic 3-, 4-, and 6-deoxy-LeX variants were also shown to form complexes in the presence of calcium ions, despite the replacement of one of their hydroxyl groups by hydrogen atoms. This is the first direct observation in solution of a calcium-mediated interaction between LeX molecules.