NMR study on the hydroxy protons of the Lewis X and Lewis Y oligosaccharides

The ¹H NMR chemical shifts and NOEs of hydroxy protons in Lewis X trisaccharide, β-d-Galp-(1 → 4)α-l-Fucp-(1 → 3)]-β-d-GlcpNAc, and Lewis Y tetrasaccharide, α-l-Fucp-(1 → 2)-β-d-Galp-(1 → 4)α-l-Fucp-(1 → 3)]-β-d-GlcpNAc, were obtained for 85% H₂O/15% (CD₃)₂CO solutions. The OH-4 signal of Galp in Lewis X and OH-3, OH-4 signals of Galp, and OH-2 signal of Fucp linked to Galp in Lewis Y had chemical shifts which indicate reduced hydration due to their proximity to the hydrophobic face of the Fucp unit linked to GlcpNAc. The inter-residue NOEs involving the exchangeable NH and OH protons confirmed the stacking interaction between the Fucp linked to the GlcpNAc and the Galp residues in Lewis X and Lewis Y.