title: Semisynthesis and insecticidal activity of some fraxinellone derivatives modified in the B ring.
abstract: 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.
authors.affiliation: Laboratory of Pharmaceutical Design and Synthesis, College of Sciences, Northwest A&F University , Yangling 712100, Shaanxi Province, People's Republic of China .
authors.forename: Yong
authors.initials: Y
authors.lastname: Guo
authors.forename: Huan
authors.initials: H
authors.lastname: Qu
authors.forename: Xiaoyan
authors.initials: X
authors.lastname: Zhi
authors.forename: Xiang
authors.initials: X
authors.lastname: Yu
authors.forename: Chun
authors.initials: C
authors.lastname: Yang
authors.forename: Hui
authors.initials: H
authors.lastname: Xu
mesh_terms: D000818:Animals; D001572:Benzofurans / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D007306:Insecticides / Q000138:chemical synthesis / Q000737:chemistry* / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000254:growth & development; D015394:Molecular Structure; D009036:Moths / Q000187:drug effects / Q000254:growth & development; D013329:Structure-Activity Relationship
chemical_list: D001572:Benzofurans; D007306:Insecticides; C075391:fraxinellone