| 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 atB3LYP-SCRF/6-31G*//B3LYP/6-31G* level with COSMO model, permitted unequivocal assignmentof its 2R,3S absolute configuration. The experimentally observed Cotton effect (CE) around 290 nm iscontributed by the acetophenone π → π* transition of the ABC-flavanone moiety and the electronictransition within the DEF-flavone moiety, while another diagnostic positive CE around 350 nm isattributable 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 thecalculated ECD of its two rotamers indicate that the rotational restrictions significantly affect the ECDof 3,8‘ ‘-biflavonoids. Empirical ECD rules derived from monomeric flavonoids may not be applicable toconfigurational assignment of complex 3,8‘ ‘-biflavonoids. This study has provided new insights ininterpreting the experimentally observed ECD spectra of this class of compounds.
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