DFT and NMR parameterized conformation of valeranone

Abstract

A Monte Carlo random search using molecular mechanics, followed by geometry optimization of each minimum energy structure employing density functional theory (DFT) calculations at the B3LYP/6-31G* level and a Boltzmann analysis of the total energies, generated accurate molecular models which describe the conformational behavior of the antispasmodic bicyclic sesquiterpene valeranone (1). The theoretical H-C-C-H dihedral angles gave the corresponding 1H, 1H vicinal coupling constants using a generalized Karplus-type equation. In turn, the 3J(H,H) values were used as initial input data for the spectral simulation of 1, which after iteration provided an excellent correlation with the experimental 1H NMR spectrum. The calculated 3J(H,H) values closely predicted the experimental values, excepting the coupling constant between the axial hydrogen alpha to the carbonyl group and the equatorial hydrogen beta to the carbonyl group (J(2beta, 3beta)). The difference is explained in terms of the electron density distribution found in the highest occupied molecular orbital (HOMO) of 1. The simulated spectrum, together with 2D NMR experiments, allowed the total assignment of the 1H and 13C NMR spectra of 1.

Polycyclohexanes: Quantum-chemical models

“…1) that the calculated parameters of cyclohexane are very consistent with the theoretical data reported previously [18,19], as well as with the experimental data obtained by microwave spectroscopy [20]. Appropriate reproduction of geometric parameters of saturated compounds by B3LYP calculations using different basis sets was noted previously [21][22][23][24]. …”

Natural sesquiterpenoids

“…261 An enantioselective synthesis of the 1,10-seco-eudesmanolides eriolanin and eriolangin has been achieved. 262 An enantiospecific total synthesis 263 and a conformational study 264 of valeranone have been carried out. In the latter work molecular mechanics calculations and nuclear magnetic resonance were utilized.…”

Kanokonyl Acetate-Rich Indian Valerian from Northwestern Himalaya

“…Although its analogues, hydroxyvaleranone, acetylhydroxyvaleranone and 15-acetoxyvaleranone were earlier reported from V. wallichii, V. italica, V. fauriei and V. tuberosa[10,12,13], the spectral data ( 1 H and13 C NMR) of isolated compound 1 is comparable with kanokonyl acetate[13]. Kanokonol and kanokonyl acetate have previously been characterized in Japanese Valerian by 1 H NMR spectroscopy[14,15]. Hikino et al(1965) have especially emphasized that, although the Indian workers isolated kanokonol from an Indian valerian, similar to that in the Japanese report, they presented no persuasive evidence about its stereochemistry and did…”