Discovery of Oxime Ether Derivatives with High Insecticidal Activity against Plutella xylostella via an Isosteric Ring Exchange Strategy

Abstract Nitrogen-containing heterocycles rank among the most prevalent pharmacophores in agrochemicals and are widely utilized for replacing benzene rings during lead compound optimization. A total of 48 novel target compounds were designed and synthesized via structural modification of an oxime ether insecticidal lead previously found by our group. Bioassays against Mythimna separata, Plutella xylostella, and Aedes aegypti proved that 19a, 20a, and 21a possessed favorable insecticidal activity. Specifically, compound 19a exerted strong stomach toxicity against P. xylostella with an LC50 of 0.75 mg/L, which was far better than that of commercial fipronil (6.60 mg/L). Moreover, compound 19a also presented a remarkable contact toxicity. TEM analysis confirmed that it severely damaged pest midgut tissues, triggering pathological changes similar to those of botanical celangulin V. Accordingly, such oxime ethers are promising candidates for P. xylostella control.