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

Abstract

The electronic circular dichroism (ECD) and vibrational circular dichroism (VCD) spectra of both enantiomers of naringenin (4',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 cm(-1). 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.

Biomimetic synthesis and HPLC–ECD analysis of the isomers of dracocephins A and B

“…For the validation of our computational approach on flavonoids, the ECD spectra of ( R )-naringenin (( R )- 1 ), the building blocks of dracocephins A and B, were calculated first with different methods to identify which is able to reproduce most precisely the experimental ECD transitions. ECD and VCD calculations of naringenin have been reported recently by Abbate et al, which could serve as a good basis for our computational studies [7]. Naringenin is a flavanone derivative, whose negative 327 nm n–π* Cotton effect (CE) and the positive 289 nm π–π* CE were correlated with M helicity of the fused hetero ring and (2 R ) absolute configuration [8–9].…”

Three New Oligostilbenes from the Seeds of Paeonia suffruticosa

“…14,15) As shown in Fig. 3, the calculations of the ECD spectra for these structures and their arithmetical averaging provided the overall theoretical ECD spectrum.…”

Vibrational and electronic circular dichroism spectroscopies and DFT calculations for the assignment of the absolute configuration of hydroxy-substituted 2-tetralols

“…This finding of the pseudo-axial conformer has been also pointed out in another context by Muñoz et al,25 This work will be useful to compare other natural products data to. 26 We think that the above conclusions, regarding the assignment of the absolute configuration and the conformations, are valid independent of the type of substituent in the cyclohexane moiety; this is seen by comparing 1a and 1b (1-tetralol and 1-aminotetralin), though with different population factors. We expect this to be valid also for 2-tetralol and 2-aminotetralin, for which studies are under way.…”