Synthesis and insecticidal activity of 1-phenyl-5-aminopyrazole ecdysteroid analogs

To develop highly efficient and structurally novel insect growth regulators, 20 1-phenyl-5-amino pyrazoles were designed and synthesized using ecdysteroid receptor (EcR) as the target and I7 (N-4-cyano-1-phenyl-1H-pyrazol-5-yl)-2-phenylacetamide), a highly active compound discovered by our group, as a lead. All synthesized structures were confirmed by ¹H NMR, ¹³C NMR and HRMS. The insecticidal activity of the compounds showed that the lethality of compounds M10, M17, M18 was more than 20% higher than that of lead compound I7 (60%) at a concentration of 250 mg/L. Compound M10 was the most active, exhibiting a lethality rate of 60% at 125 mg/L, which is slightly lower than that of the commercial tebufenozide (70%), and the Plutella xylostella treated with this compound showed typical symptoms of ecdysteroid analogue poisoning. The results of the target binding activity of PxEcR showed that the compounds M2, M6, M9, M12, M13, M15 and M20 were better than that of compound I7, and that the target binding activity of compound M15 (IC₅₀(PxEcR) = 2.02 μmol/L) was 11.5 times higher than that of compound I7 (IC₅₀(PxEcR) = 23.21 μmol/L). The binding mechanism between compounds I7, M10, M15 and EcR receptor was further analyzed by molecular docking and molecular dynamics simulation, which will provide guidance for the further research on insect growth regulators targeting EcR.