Importance of solvation in understanding the chiroptical spectra of natural products in solution phase: garcinia acid dimethyl ester.

Polavarapu PL, Scalmani G, Hawkins EK, Rizzo C, Jeirath N, Ibnusaud I, Habel D, Nair DS, Haleema S
J Nat Prod. 2011 74 (3): 321-8

PMID: 21114277 · PMCID: PMC3699186 · DOI:10.1021/np100512w

The optical rotatory dispersion (ORD), electronic circular dichroism (ECD), and vibrational circular dichroism (VCD) spectra of (+)-garcinia acid dimethyl ester have been measured and analyzed by comparison with the corresponding spectra predicted by quantum chemical methods for (2S,3S)-garcinia acid dimethyl ester. For solution-phase calculations the recently developed continuous surface charge polarizable continuum model (PCM) has been used. It is found that gas-phase predictions and PCM predictions at the B3LYP/aug-cc-pVDZ level yield nearly mirror-image ECD spectra in the 190-250 nm region for the same absolute configuration and that gas-phase ECD predictions lead to incorrect absolute configuration. At the CAM-B3LYP/aug-cc-pVDZ level, however, gas-phase predictions and PCM predictions of ECD in the 190-250 nm region are not so different, but PCM predictions provide better agreement with the experimental observations. For carbonyl stretching vibrations, the vibrational band positions predicted at the B3LYP/aug-cc-pVDZ level in gas-phase calculations differ significantly from the corresponding experimentally observed band positions, and this discrepancy has also been corrected by the use of PCM. In addition, the solution-phase VCD predictions provided better agreement (with experimental VCD observations) than gas-phase VCD predictions. These observations underscore the importance of including solvent effects in quantum chemical calculations of chiroptical spectroscopic properties.

MeSH Terms (7)

Circular Dichroism Citrates Garcinia Models, Molecular Molecular Structure Optical Rotatory Dispersion Stereoisomerism

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