Stephens, P. J. Pan, J. J. Devlin, F. J. Krohn, K. Kurtán, T. Determination of the Absolute Configurations of Natural Products via Density Functional Theory Calculations of Vibrational Circular Dichroism, Electronic Circular Dichroism, and Optical Rotation:  The Iridoids Plumericin and Isoplumericin The absolute configurations (ACs) of the iridoid natural products, plumericin (<b>1</b>) and isoplumericin (<b>2</b>), have been re-investigated using vibrational circular dichroism (VCD) spectroscopy, electronic circular dichroism (ECD) spectroscopy, and optical rotatory dispersion (ORD). Comparison of DFT calculations of the VCD spectra of <b>1</b> and <b>2</b> to the experimental VCD spectra of the natural products, (+)<b>-1</b> and (+)<b>-2</b>, leads unambiguously to the AC (1<i>R</i>,5<i>S</i>,8<i>S</i>,9<i>S</i>,10<i>S</i>)-(+) for both <b>1</b> and <b>2</b>. In contrast, comparison of time-dependent DFT (TDDFT) calculations of the ECD spectra of <b>1</b> and <b>2</b> to the experimental spectra of (+)<b>-1</b> and (+)<b>-2</b> does not permit definitive assignment of their ACs. On the other hand, TDDFT calculations of the ORD of (1<i>R</i>,5<i>S</i>,8<i>S</i>,9<i>S</i>,10<i>S</i>)<b>-1</b> and <b>-2</b> over the range of 365−589 nm are in excellent agreement with the experimental data of (+)<b>-1</b> and (+)<b>-2</b>, confirming the ACs derived from the VCD spectra. Thus, the ACs initially proposed by Albers-Schönberg and Schmid are shown to be correct, and the opposite ACs recently derived from the ECD spectra of <b>1</b> and <b>2</b> by Elsässer et al. are shown to be incorrect. As a result, the ACs of other iridoid natural products obtained by chemical correlation with <b>1</b> and <b>2</b> are not in need of revision. Density Functional Theory Calculations;AC;Electronic Circular Dichroism;VCD spectra;DFT;ORD;calculation;ECD spectra;Vibrational Circular Dichroism;TDDFT 2007-04-27
    https://acs.figshare.com/articles/journal_contribution/Determination_of_the_Absolute_Configurations_of_Natural_Products_via_Density_Functional_Theory_Calculations_of_Vibrational_Circular_Dichroism_Electronic_Circular_Dichroism_and_Optical_Rotation_The_Iridoids_Plumericin_and_Isoplumericin/3010858
10.1021/jo070155q.s001