title: Structure of a non-planar flavonol, 5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone.
abstract: C20H20O10, Mr = 420.37, triclinic, P1, a = 8.771 (3), b = 13.508 (3), c = 15.970 (4) A, alpha = 86.04 (2), beta = 81.77 (2), gamma = 84.17 (2) degrees, V = 1860.0 (8) A3, Z = 4 (two molecules per asymmetric unit), Dm (by flotation in ZnCl2/H2O solution at 298 K) = 1.491, Dx = 1.503 g cm-3, Mo K alpha radiation, lambda = 0.71069 A, mu = 1.14 cm-1, F(000) = 880, T = 163 K. Full-matrix least-squares refinement converged to R = 0.039 and wR = 0.037 using 5198 reflections with I greater than 3 sigma (I). The two molecules in the asymmetric unit differ in the torsion angles involving the methoxy groups and in the dihedral angle between the planes of rings B and C, 33.31 (7) and 40.83 (7) degrees in molecules (I) and (II), respectively. This compound belongs to a class of 3,2'-dioxygenated flavonoids whose ultraviolet (UV), mass spectroscopic (MS) and chromatographic properties indicate that in solution these compounds have reduced planarity (and thus reduced conjugation) of the B-ring chromophore with the A, C-ring chromophore.
authors.affiliation: Department of Chemistry, University of Texas, Austin 78713.
authors.forename: K A
authors.initials: KA
authors.lastname: Abboud
authors.forename: S H
authors.initials: SH
authors.lastname: Simonsen
authors.forename: T J
authors.initials: TJ
authors.lastname: Mabry
authors.forename: N
authors.initials: N
authors.lastname: Fang
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D005419:Flavonoids; D015394:Molecular Structure; D014961:X-Ray Diffraction
chemical_list: D005419:Flavonoids; C062832:5,7,2'-trihydroxy-3,6,8,4',5'-pentamethoxyflavone