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(+)- and (−)-Alternarilactone A: Enantiomers with a Diepoxy-Cage-like Scaffold from an Endophytic Alternaria sp.
- Jian-Wei Tang, Hou-Chao Xu, Wei-Guang Wang, Kun Hu, Yuan-Fei Zhou, Rong Chen, Xiao-Nian Li, Xue Du, Han-Dong Sun, Pema-Tenzin Puno
- Journal of natural products 2019 v.82 no.4 pp. 735-740
- Alternaria, X-ray diffraction, enantiomers, endophytes, fungi, moieties, nuclear magnetic resonance spectroscopy, probability analysis, quantum mechanics, risk
- The enantiomers (+)- and (−)-alternarilactone A (1), the first examples of dibenzo-α-pyrones bearing a diepoxy-cage-like moiety, were isolated from the endophytic fungus Alternaria sp. hh930. The deficiency in ¹H–¹H COSY and HMBC correlations caused by the highly oxidized caged system of 1 and the deceptive and ambiguous signals such as “W” couplings in NMR data increased the risk of structure misassignment of 1. By performing a quantum chemical calculation of the NMR chemical shifts together with a DP4+ probability analysis and single-crystal X-ray crystallographic experiment, their structures were unambiguously determined, and their absolute configurations were determined by ECD calculations.