Details

Autor(en) / Beteiligte

• Stephens, P. J
• Pan, J. J
• Devlin, F. J
• Krohn, K
• Kurtán, T

Titel

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

Ist Teil von

• Journal of organic chemistry, 2007-04, Vol.72 (9), p.3521-3536

Ort / Verlag

Washington, DC: American Chemical Society

Erscheinungsjahr

2007

Quelle

MEDLINE

Beschreibungen/Notizen

• The absolute configurations (ACs) of the iridoid natural products, plumericin (1) and isoplumericin (2), 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 1 and 2 to the experimental VCD spectra of the natural products, (+)-1 and (+)-2, leads unambiguously to the AC (1R,5S,8S,9S,10S)-(+) for both 1 and 2. In contrast, comparison of time-dependent DFT (TDDFT) calculations of the ECD spectra of 1 and 2 to the experimental spectra of (+)-1 and (+)-2 does not permit definitive assignment of their ACs. On the other hand, TDDFT calculations of the ORD of (1R,5S,8S,9S,10S)-1 and -2 over the range of 365−589 nm are in excellent agreement with the experimental data of (+)-1 and (+)-2, 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 1 and 2 by Elsässer et al. are shown to be incorrect. As a result, the ACs of other iridoid natural products obtained by chemical correlation with 1 and 2 are not in need of revision.