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  • Title: Absolute configuration of 7,8-seco-7,8-oxacassane diterpenoids from Acacia schaffneri.
    Author: Manríquez-Torres JJ, Torres-Valencia JM, Gómez-Hurtado MA, Motilva V, García-Mauriño S, Ávila J, Talero E, Cerda-García-Rojas CM, Joseph-Nathan P.
    Journal: J Nat Prod; 2011 Sep 23; 74(9):1946-51. PubMed ID: 21894904.
    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.
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