In order to find new semicarbazide lead compounds, ten N-[1-(2,6-dicholoro-4-trifluoromethyl- phenyl)-1H-pyrazol-5-yl]-chrysanthemumamides were synthesized from five types of chrysanthemic acids with fipronil or 5-amino-1-(2,6-dichloro-4-trifluoromethylphenyl)-1H-pyrazol-3-carbonitrile. The structures of all new compounds were confirmed by ¹H NMR, MS spectra and elemental analysis. At the concentration of 37.5 mg/L, compound 3b shows inhibitory activity (100%) against Plutella xylostella Linnaeus. The LC₅₀ of this compound is 15.1 mg/L. The oral acute toxicity of this compound to big male and female rats is middle. The crystal structure of 3i is also presented. The results indicate that it is rational and feasible to find new active compounds based on the connection between the active compound and the pharmacophore.

Key words: insecticidal activity, N-arylpyrazole, single crystal, toxicity