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

Authors: Polavarapu, Prasad L; Scalmani, Giovanni; Hawkins, Edward K; Rizzo, Carmelo; Jeirath, Neha; Ibnusaud, Ibrahim; Habel, Deenamma; Nair, Divya Sadasivan; Haleema, Simimole

Published In J Nat Prod, (2011 Mar 25)

Abstract: 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.

PubMed ID: 21114277 Exiting the NIEHS site

MeSH Terms: Circular Dichroism; Citrates/chemistry*; Garcinia/chemistry; Models, Molecular*; Molecular Structure; Optical Rotatory Dispersion; Stereoisomerism

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