Vibrational and theoretical studies of a sesquiterpene lactone, 11αH-dihydrozaluzanin E

Infrared vibrational spectrum of 11αH-dihydrozaluzanin E has been measured at room temperature and it was analyzed theoretically by means of ab initio calculations. The conformational space of the compound has been scanned using molecular dynamics and complemented with functional density calculations that optimize the geometry of the lowest-energy conformers of each species as obtained in the simulations. The vibrational frequencies were assigned using functional density calculations. The Molecular Electrostatic Potential Map (MEP) was obtained and analyzed. Coupling constants were calculated at ab initio level and by means of the Karplus-Calculator method and via the MestRe-J Program, chemical shifts were also calculated at ab initio level and all the results were compared with respect to experimental data. Conclusions are reported on the stereochemistry of the molecule.