The electronic circular dichroism (ECD) spectra of two sesquiterpenoids (1 and 2) related to oplopanone, obtained from a methanolic extract of the plant Serphidium stenocephalum (Artemisia stenocephala), were measured and reproduced by means of time-dependent density functional theory (TDDFT) calculations, establishing their absolute configuration. The application of ketone octant rule for carbonyl n-* ECD band to compounds 1 and 2, which include an acyclic carbonyl group, was critically assessed. The peculiar oplopanone skeleton makes a straightforward application of the octant rule impossible, because of the uncertainty related to the shape of the so-called third nodal surface separating front and back octants. The various group contributions to the carbonyl n-* ECD band were estimated with TDDFT calculations on selected molecular models obtained by consecutive dissections from 1. Chirality 26:39-43, 2013. (c) 2013 Wiley Periodicals, Inc.
Absolute Configuration of Oplopanone Derivatives From Serphidium stenocephalum: ECD Spectra of Acyclic Ketones With Front-Octant Contributions
PESCITELLI, GENNARO
2014-01-01
Abstract
The electronic circular dichroism (ECD) spectra of two sesquiterpenoids (1 and 2) related to oplopanone, obtained from a methanolic extract of the plant Serphidium stenocephalum (Artemisia stenocephala), were measured and reproduced by means of time-dependent density functional theory (TDDFT) calculations, establishing their absolute configuration. The application of ketone octant rule for carbonyl n-* ECD band to compounds 1 and 2, which include an acyclic carbonyl group, was critically assessed. The peculiar oplopanone skeleton makes a straightforward application of the octant rule impossible, because of the uncertainty related to the shape of the so-called third nodal surface separating front and back octants. The various group contributions to the carbonyl n-* ECD band were estimated with TDDFT calculations on selected molecular models obtained by consecutive dissections from 1. Chirality 26:39-43, 2013. (c) 2013 Wiley Periodicals, Inc.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
