10.1021/jo070155q.s001
P. J. Stephens
P. J.
Stephens
J. J. Pan
J. J.
Pan
F. J. Devlin
F. J.
Devlin
K. Krohn
K.
Krohn
T. Kurtán
T.
Kurtán
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
American Chemical Society
2007
Density Functional Theory Calculations
AC
Electronic Circular Dichroism
VCD spectra
DFT
ORD
calculation
ECD spectra
Vibrational Circular Dichroism
TDDFT
2007-04-27 00:00:00
Journal contribution
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
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.