title: Vibrational circular dichroism of Africanane and lippifoliane sesquiterpenes from Lippia integrifolia.
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.
authors.affiliation: Departamento de Química, Centro de InVestigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000 México. ccerda@cinvestav.mx
authors.forename: Carlos M
authors.initials: CM
authors.lastname: Cerda-García-Rojas
authors.forename: César A N
authors.initials: CA
authors.lastname: Catalán
authors.forename: Ana C
authors.initials: AC
authors.lastname: Muro
authors.forename: Pedro
authors.initials: P
authors.lastname: Joseph-Nathan
mesh_terms: D002942:Circular Dichroism; D032411:Lippia / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010946:Plants, Medicinal / Q000737:chemistry*; D012717:Sesquiterpenes / Q000737:chemistry* / Q000302:isolation & purification*; D013237:Stereoisomerism
chemical_list: D012717:Sesquiterpenes