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  • Title: Absolute configuration of oplopanone derivatives from Serphidium stenocephalum: ECD spectra of acyclic ketones with front-octant contributions.
    Author: Shafiq N, Saleem M, Riaz N, Tousif MI, Jabbar A, Tareen RB, Pescitelli G.
    Journal: Chirality; 2014 Jan; 26(1):39-43. PubMed ID: 24254980.
    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-π* 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-π* ECD band were estimated with TDDFT calculations on selected molecular models obtained by consecutive dissections from 1.
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