DRF-1042

The antifeedant activities of camptothecin 1 and its semisynthetic derivatives 2-12 were evaluated against an economically important pest, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae).Simple chem. conversions were carried out on the natural camptothecin obtained from a Chinese medicinal plant Camptotheca acuminate.These conversions focused on different functional modified sites in the camptothecin skeleton considered to be important for the biol. activity.Among all the tested compounds, compounds 4, 5, 7 and 8 displayed more promising antifeedant activity than camptothecin 1.Especially compound 7 was found to exhibit exceptionally potent antifeedant activity with AFC₅₀ values of 92.03μg/mL, compared to 1 and toosendanin, a com. insecticide derived from Melia azedarach (IC₅₀ 528.40μg/mL and 91.68μg/mL, resp.).The different antifeedant activity range of compounds 1-12 indicated that variation of chem. structures in the camptothecin skeleton markedly affected the activity profiles of this compound class, and some preliminary SAR information was observed from it.

Continuing our search for natural product based compounds for the control of Brontispa longissima larvae, eight spin‐labeled camptothecin derivatives 7a–h and the intermediate 2 were first tested for their insecticidal activities against fifth‐instar larvae of Brontispa longissima. Among all the tested compounds, especially compounds 7a and 2 showed promising insecticidal activities with the corrected mortality rates of 69.55% and 74.07% against fifth‐instar larvae of B. longissima, respectively. The different insecticidal activity ranges of these compounds indicated that the variation of the structures of l‐amino acids in these compounds markedly affected the activity profiles of this compound class, and some important SAR information has been revealed from it. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:687–691, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/hc.20734