In order to find new protoporphyrinogen oxidase inhibitors, a series of novel 3H-pyrazolo- [3,4-d][1,2,3]triazin-4-one derivatives were designed and synthesized according to biorational design. The target molecules were synthesized by diazotization of different 5-amino-N-phenyl-1H-pyrazole-4- carbox-amide derivatives prepared by a reaction of substituted 5-amino-pyrazole-4-carbonyl chloride with substi-tuted anilines. Different halides were reacted with 3f to afford the pure target products 3g～3w respectively. Their structures were identified by 1H NMR, IR spectra and elemental analyses. The bioassay results showed that some of the title compounds exhibited high inhibition against protoporphyrinogen oxidase activity in vi-tro. The structure-activity relationship was discussed.

Key words: synthesis, protoporphyrinogen oxidase (PPO), bioac-tivi, 3H-pyrazolo[3,4-d][1,2,3]triazin-4-one