Synthesis and Bioactivity of N-(5′-Bromo-4′-substituted pyrimidin-2′-yl)phenyl Sulfonylurea

Acetohydroxy acid synthase (AHAS) catalyzes the key reactions in the biosynthesis pathways of branched-chain amino acids (valine, isoleucine and leucine) in plants and microorganisms, and sulfonylurea herbicides are inhibitors of AHAS, characterized by high herbicidal activity, high degree of selectivity, and excellent environmental safety. A series of 5-bromopyrimidinyl-containing new sulfonylureas have been synthesized through bromination of 2-amino-4-methyl pyrimidine, followed by further modification and then coupled with sulfonyl isocyanate. Their structures were confirmed by H-1 NMR, MS techniques and elemental analysis. Preliminary bioassay of sulfonylureas showed that the title compounds exhibited good in vitro activities against E. coli acetohydroxy acid synthase isoenzyme AHASII but showed lower herbicidal activities in vivo, compared with commercial herbicide tribenuron-methly.