Oligosaccharides Related to Tumor-Associate Antigens. Part 2. Conformational analysis of the trisaccharide α-L-Fucp-(1→2)-β-D-Galp-(1→3)-β-D-GalpNAc, epitope structure recognized by the MBr1 antibody

The conformational space of the trisaccharide α-L-Fuc-(1 → 2)-β-D-Gal-(1 → 3)-β-D-GalNAc-1-OPr (2) and of its component disaccharide moieties α-L-Fuc-(1 → 2)-β-D-Gal-1-OMe (3) and β-D-Gal-(1 → 3)-β-D-GalNAc-1-OPr (4) was investigated with the aid of molecular-mechanics energy minimizations and molecular-dynamics simulations. These calculations suggested the occurrence of two conformations for each compound characterized by different Φ and ψ glycosidic angles. However, 1H-NMR investigation of D2O solutions of 2-4 indicated a sure preference for one of the two conformers with a contribution of the other one ranging from negligible to low.