Design, Synthesis and Biological Evaluation of Novel Pyrazole Sulfonamide Derivatives as Potential AHAS Inhibitors.

Acetohydroxy acid synthase (AHAS; EC 2.2.1.6, also referred to as acetolactate synthase, ALS) has been considered as an attractive target for the design of herbicides. In this work, an optimized pyrazole sulfonamide base scaffold was designed and introduced to derive novel potential AHAS inhibitors by introducing a pyrazole ring in flucarbazone. The results of in vivo herbicidal activity evaluation indicates compound 3b has the most potent activity with rape root length inhibition values of 81% at 100 mg/L, and exhibited the best inhibitory ability against Arabidopsis thaliana AHAS. With molecular docking, compound 3b insert into Arabidopsis thaliana AHAS stably by an H-bond with Arg377 and cation-π interactions with Arg377, Trp574, Tyr579. This study suggests that compound 3b may serve as a potential AHAS inhibitor which can be used as a novel herbicides and provides valuable clues for the further design and optimization of AHAS inhibitors.