Insight into reduction of obacunone, and their ester derivatives as insecticidal agents against Mythimna separata Walker

Abstract

Here we have prepared a series of ester compounds of obacunone, a naturally occurring limonoid, isolated from plants such as Citrus and Dictamnus angustifolius. Their insecticidal activity was evaluated at 1 mg/mL against the pre-third-instar larvae of oriental armyworm (Mythimna separata Walker), a typical lepidopteran pest. When obacunone reacted with NaBH₄, the ratio of two reduction products, C7α-hydroxyobacunone (2) and C7β-hydroxyobacunone (3), was related to the reaction mixing solvents. C7α-Propionyloxybacunone (4b) and C7β-(n)heptanoyloxybacunone (5g) exhibited the more promising insecticidal activity than their precursor obacunone and toosendanin.