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Absolute configuration of lippifoliane and africanane derivatives
Carlos M Cerda-García-Rojas1, Angelina del C Coronel, Marina E P de Lampasona
1Departamento de Química, Centro de Investigación y de Estudios Avanzados del Instituto Politécnico Nacional, Apartado 14-740, México, D. F., 07000 México. ccerda@cinvestav.mx
Abstract:
The absolute configuration of naturally occurring lippifoliane derivatives isolated from the widely used plant Lippia integrifolia was assigned by analysis of the circular dichroism data in combination with density functional theory minimum energy molecular models of (1S,4R,6S,9S,10R)-lippifolian-1-ol-5-one (1), (4R,9S,10R)-lippifoli-1(6)-en-5-one (2), and (4S,9S,10R)-lippifoli-1(6)-en-4-ol-5-one (3) and application of the octant rule for saturated ketone 1 and the helicity rules for alpha,beta-unsaturated ketones 2 and 3. The results were reinforced by the anomalous dispersion effect observed in the X-ray diffraction analysis of (4S,9S,10R)-4,10,11-tribromo-10,11-seco-lippifoli-1(6)-en-5-one (4) prepared from 2. The biogenetic relationships between lippifolianes 1-3 and africanane derivatives 7-9 and 13 isolated from the same species, together with chiroptical data for africananes isolated from the Hepaticae family, complete a stereochemical scenario in relation to the absolute configuration of africananes from L. integrifolia.
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