title: Absolute configuration of 7,8-seco-7,8-oxacassane diterpenoids from Acacia schaffneri.
abstract: Chemical investigations of Acacia schaffneri led to the isolation of the new diterpenoid (5S,7R,8R,9R,10S)-(-)-7,8-seco-7,8-oxacassa-13,15-diene-7,17-diol (1), together with the known (5S,7R,8R,9R,10S)-(-)-7,8-seco-7,8-oxacassa-13,15-dien-7-ol-17-al (2) and (5S,7R,8R,9R,10S)-(-)-7,8-seco-7,8-oxacassa-13,15-dien-7-ol (3). Compounds 2 and 3 were analyzed by single-crystal X-ray diffraction, while the structure of 1 was determined by 1D and 2D NMR experiments and by chemical correlation with 2. Oxidation of 3 afforded conformationally restricted (5S,8R,9R,10S)-(-)-8-hydroxy-7,8-seco-cassa-13,15-dien-7-oic acid ε-lactone (4), which was studied by vibrational circular dichroism spectroscopy. Comparison of the experimental VCD spectrum of 4 with the DFT//B3PW91/DGDZVP2 calculated spectrum assigned for the first time the absolute configuration of these seco-oxacassane diterpenes.
authors: Área Académica de Química, Universidad Autónoma del Estado de Hidalgo, Km 4.5 Carretera Pachuca-Tulancingo, Mineral de la Reforma, Hidalgo, 42184 Mexico.
authors: J Jesús
authors: JJ
authors: Manríquez-Torres
authors: J Martín
authors: JM
authors: Torres-Valencia
authors: Mario A
authors: MA
authors: Gómez-Hurtado
authors: Virginia
authors: V
authors: Motilva
authors: Sofía
authors: S
authors: García-Mauriño
authors: Javier
authors: J
authors: Ávila
authors: Elena
authors: E
authors: Talero
authors: Carlos M
authors: CM
authors: Cerda-García-Rojas
authors: Pedro
authors: P
authors: Joseph-Nathan
mesh_terms: D000045:Acacia / Q000737:chemistry*; D002942:Circular Dichroism; D018360:Crystallography, X-Ray; D004224:Diterpenes / Q000737:chemistry* / Q000302:isolation & purification*; D007783:Lactones / Q000737:chemistry / Q000302:isolation & purification; D008800:Mexico; D008958:Models, Molecular; D008968:Molecular Conformation; D015394:Molecular Structure; D010084:Oxidation-Reduction; D013237:Stereoisomerism
chemical_list: D004224:Diterpenes; D007783:Lactones