title: Theoretical calculation of electronic circular dichroism of the rotationally restricted 3,8''-biflavonoid morelloflavone.
abstract: Theoretical calculation of electronic circular dichroism (ECD) of the rotationally restricted 3,8''-biflavonoid (+)-morelloflavone using time dependent density functional theory (TDDFT), performed at 298 K at B3LYP-SCRF/6-31G*//B3LYP/6-31G* level with COSMO model, permitted unequivocal assignment of its 2R,3S absolute configuration. The experimentally observed Cotton effect (CE) around 290 nm is contributed by the acetophenone pi --> pi* transition of the ABC-flavanone moiety and the electronic transition within the DEF-flavone moiety, while another diagnostic positive CE around 350 nm is attributable to the electronic interaction between the ABC-flavanone moiety and the DEF-flavone moiety, as well as the electronic transition within the DEF-flavone moiety. The remarkable differences of the calculated ECD of its two rotamers indicate that the rotational restrictions significantly affect the ECD of 3,8''-biflavonoids. Empirical ECD rules derived from monomeric flavonoids may not be applicable to configurational assignment of complex 3,8''-biflavonoids. This study has provided new insights in interpreting the experimentally observed ECD spectra of this class of compounds.
authors.affiliation: National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, and Department of Pharmacognosy, School of Pharmacy, The University of Mississippi, University, MS 38677, USA.
authors.forename: Yuanqing
authors.initials: Y
authors.lastname: Ding
authors.forename: Xing-Cong
authors.initials: XC
authors.lastname: Li
authors.forename: Daneel
authors.initials: D
authors.lastname: Ferreira
mesh_terms: D000465:Algorithms; D044946:Biflavonoids / Q000737:chemistry*; D002942:Circular Dichroism / Q000379:methods*; D004581:Electronics; D008962:Models, Theoretical; D015394:Molecular Structure; D011789:Quantum Theory
chemical_list: D044946:Biflavonoids; C105620:morelloflavone