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  • Title: Vibrational circular dichroism of Africanane and lippifoliane sesquiterpenes from Lippia integrifolia.
    Author: Cerda-García-Rojas CM, Catalán CA, Muro AC, Joseph-Nathan P.
    Journal: J Nat Prod; 2008 Jun; 71(6):967-71. PubMed ID: 18500843.
    Abstract:
    The agreement between theoretical and experimental vibrational circular dichroism curves of (4R,9R,10R)-(+)-african-1(5)-ene-2,6-dione (1) and (4R,9S,10R)-lippifoli-1(6)-en-5-one (2), isolated from the widely used plant Lippia integrifolia, allowed the determination of the conformation and absolute configuration of 1 and confirmed both structural features for 2. Molecular modeling of 1 and 2 was carried out by means of a systematic and a Monte Carlo search protocol followed by geometry optimization employing density functional theory calculations with the B3LYP/6-31G(d), B3LYP/DGDZVP, and/or B3PW91/DGDZVP2 functionals/basis sets. Validation of the minimum energy conformations for both tricyclic substances was achieved by comparison of the experimental and theoretical vicinal (1)H-(1)H NMR coupling constants obtained by DFT-GIAO calculations.
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