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.