Title
5,7-Dihydroxy-2-(4-hydroxyphenyl)chroman-4-one (naringenin): X-ray diffraction structures of the naringenin enantiomers and DFT evaluation of the preferred ground-state structures and thermodynamics for racemization
Author
Volodymyr V. Nesterov, Lev N. Zakharov, Vladimir N. Nesterov, Jose G. Calderon, Antonella Longo, Khadiza Zaman, Feroza Kaneez Choudhury, William Farrell, Vladimir Shulaev, Michael G. Richmond
Year
2016
Journal
Journal of Molecular Structure
Abstract
The R- and S-enantiomers of naringenin were separated by chiral HPLC and the absolute configuration of each enantiomer was established by X-ray crystallography. The solid-state data is in agreement with the reported circular dichroism spectra. Both enantiomers crystallize in the monoclinic crystal system in the space group P21 with two independent molecules in the asymmetric unit. In all molecules, the pyrone ring adopts a flattened chair-like conformation in which the C1 atom deviates from the plane drawn through the remaining five atoms of this heterocycle. The 4-hydroxyphenyl substituent located at C1 of the pyrone ring occupies an equatorial position and lies in a plane that is almost perpendicular to the aromatic platform associated with the heterocyclic portion of the molecule. Strong intramolecular Osingle bondH⋯O hydrogen bonding exists between the carbonyl moiety and the aryl hydroxyl group at C5. In both enantiomers, a favorable mutual orientation of two independent molecules promotes the formation of intermolecular Osingle bondH⋯O hydrogen bonds that link them into dimers. There are additional long-range intermolecular Osingle bondH⋯O hydrogen bonds and weak Csingle bondH⋯O contacts within the unit cell of each enantiomer that connect dimers in an extended network. DFT calculations have been performed and the thermodynamics for naringenin racemization via an acyclic chalcone have been computed. Eight energetically accessible conformations have been verified for S-naringenin.
Instrument
J-815
Keywords
Circular dichroism, Stereochemistry