Vibrational Circular Dichroism of Africanane and Lippifoliane Sesquiterpenes from Lippia integrifolia

C. M. CERDA-GARCÍA-ROJAS, C. A. N. CATALÁN, A. C. MURO AND P. JOSEPH-NATHAN

JOURNAL OF NATURAL PRODUCTS

American Chemical Society and American Society of Pharmacognosy

Año: 2008 vol. 71 p. 967 - 971

0163-3864

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 absolute configuration of 1 and confirmed both structural features for 2. Molecular modeling of 1 and 2  was carried out by means of a systematics and Monte Carlo search protocol followed by geometry optimization employing density functional theory calculations with B3LYP/6-31G(d), B3LYP/DGDZVP, and/or B3PW91/DGDZVP2 functional basis sets. Validation of the minimum energy conformations for both tricyclic substances was achieved by comparison of the experimental and theoretical vicinal 1H-1H NMR coupling constants obtained by DFT-GIAO calculations.