title: Conformations of Flavan-3-ols in Water: Analysis Using Density Functional Theory.
abstract: To elucidate the conformations and their relative stabilities of flavan-3-ols in water, the optimized structures and energies were calculated by density functional theory, in which M06-2X, ωB97X-D, B3LYP, and CAM-B3LYP were examined as exchange-correlation functionals. The results were evaluated by comparing calculated spin-spin coupling constants of vicinal protons with the corresponding values observed in experimental1H NMR spectra in D2O. The M06-2X and ωB97X-D results showed good agreement with the experimental NMR data and revealed that the B-ring (pseudoequatorial)/3-O (pseudoaxial) conformers were more stable [5.4-8.7 kJ/mol (1.3-2.1 kcal/mol)] than the B-ring (pseudoaxial)/3-O (pseudoequatorial) conformers in the 2,3-cis-flavan-3-ols, while the B-ring (pseudoequatorial)/3-O (pseudoequatorial) conformers and the B-ring (pseudoaxial)/3-O (pseudoaxial) conformers had similar stabilities in the 2,3-trans-flavan-3-ols.
authors.affiliation: Food Research Institute, National Agriculture and Food Research Organization (NARO) , 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Nobuyuki
authors.identifier: 0000-0002-0197-2405
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Food Research Institute, National Agriculture and Food Research Organization (NARO) , 2-1-12 Kannondai, Tsukuba, Ibaraki 305-8642, Japan.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Ujihara
mesh_terms: D005419:Flavonoids / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D019906:Nuclear Magnetic Resonance, Biomolecular; D011522:Protons; D014867:Water / Q000737:chemistry*
chemical_list: D005419:Flavonoids; D011522:Protons; D014867:Water; C404987:flavan-3-ol