Assessment of configurational and conformational properties of Naringenin by vibrational circular dichroism

The electronic circular dichroism (ECD) and vibrational circular dichroism
(VCD) spectra of both enantiomers of naringenin (40,5,7-trihydroxyflavanone) in
acetonitrile solution have been measured. The enantiomers were obtained by chiral
HPLC separation of the racemic sample. DFT calculations have been performed for relevant
conformers and subsequent evaluations of VCD spectra are compared with VCD
experiments: safe assignment of the absolute configuration is provided, based in particular
on the VCD data. The relevance of the rotational conformers of the hydroxyl groups
and of the mobility of phenol moiety is studied: based on this, we provide a first interpretation
of the observed intense and broad couplet at 1325/1350 cm21. Four conformers
contribute to this pattern with different sign and amplitude as shown by DFT calculations.
Time dependent DFT calculations have been performed and compared with
ECD experimental data, under the same assumption of conformational properties and
mobilities investigated by VCD.