- Antifungal alkaloids and limonoid derivatives from Dictamnus dasycarpus
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From the root bark of Dictamnus dasycarpus (Rutaceae), four limonoid derivatives, two furoquinoline alkaloids, five limonoids, two sesquiterpenes and three steroids were isolated and their structures elucidated on the basis of various spectroscopic method
- Zhao, Weimin,Wolfender, Jean-Luc,Hostettmann, Kurt,Xu, Rensheng,Qin, Guowei
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- Semisynthesis and insecticidal activity of some fraxinellone derivatives modified in the B ring
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A series of novel fraxinellone derivatives modified at the C-1 or C-8 position in the B ring were prepared as insecticidal agents against the pre-third-instar larvae of oriental armyworm, Mythimna separata Walker at 1 mg/mL. Five key steric configurations of compounds 2, 3, and 8f,g,j were further determined by single-crystal X-ray diffraction. It was found that the kinds and the amount of the reduction products of fraxinellone were related to the molar ratio between the reduction agent Red-Al and the substrate fraxinellone. Among all of the derivatives, compounds 2 and 8i,j,o displayed more promising insecticidal activity than their precursors fraxinellone and toosendanin. The preliminary structure-activity relationships revealed that the lactone (B-ring) of fraxinellone contributed to the observed insecticidal activity; the double bond at the C-2 position of fraxinellone was not necessary for the insecticidal activity; conversion of the oxygen atom of carbonyl group on the lactone of fraxinellone to a sulfur one does not improve the insecticidal activity; introduction of electron-withdrawing groups on the phenyl ring of 8f, to the benzoyloxy series, could result in more potent compounds.
- Guo, Yong,Qu, Huan,Zhi, Xiaoyan,Yu, Xiang,Yang, Chun,Xu, Hui
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p. 11937 - 11944
(2014/01/06)
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