Crystal state and solution conformation of the B blood group trisaccharide...

The crystal structure of the human B blood group related trisaccharide alpha-L-Fucp-(1-->2)-[alpha-D-Galp]-(1-->3)-beta-D-Galp-OCH3 (1) has been determined. The solution structure of 1 was studied by two-dimensional NMR techniques at 600 MHz in D2O solution and the conformational properties were analyzed in terms of the torsional angles phiH and psiH, derived from 3JCH coupling constants, and 10 inter-residue proton-proton distances. 3JCH could be accurately measured by a recently introduced two-dimensional heteronuclear correlation experiment (EXSIDE). The nuclear Overhauser enhancement-derived distances and the calculated torsion angles were compared with the same information available from the crystal structure. The agreement is excellent, indicating that the trisaccharide adopts a restricted conformation in solution, which was also predicted by the Hard Sphere Exo-Anomeric forcefield. The data of 1 are complemented by NMR studies of the closely related alpha-L-Fucp-(1-->2)-[6-deoxy-alpha-D-Galp]-(1-->3)-beta-D-Galp O-(CH2 )7CH3 trisaccharide (2).