Relationship between structure and three-bond proton–proton coupling constants in glycosaminoglycans

Theoretical calculations using the DFT theory at the B3LYP/6-311++G∗∗ level were used to determine the molecular geometry of various glycosaminoglycan (GAG) molecules. Three-bond proton–proton spin–spin coupling constants (3JH–C–C–H) were then computed and compared with the published experimental data of selected mono- and disaccharides. The computed 3JH–C–C–H values showed a strong dependence on the molecular geometry and varied up to 12 Hz. This dependence was expressed in a simple analytical form relating 3JH–C–C–H and torsion angles. The population of conformers in heparin and other biologically active GAGs has also been estimated using the computed coupling constants.

3D Structures and three-bond proton–proton spin–spin coupling constants (3JH–C–C–H) were determined using theoretical methods in various glycosaminoglycan (GAG) molecules. The computed 3JH–C–C–H values showed a strong dependence on the molecular geometry. This dependence was expressed in a simple analytical form relating 3JH–C–C–H and torsion angles in GAGs: 3JH–C–C–H = 9.6 cos2ϕ − 0.6 cos ϕ + 0.2.