Acetohydroxyacid synthase (AHAS;also known as acetolactate synthase;EC 2.2.1.6, formerly EC 4.1.3.18) is the first common enzyme in the biosynthetic pathway leading to the branched-chain amino acids in plants and a wide range of microorganisms. Weed resistance to AHAS-inhibiting herbicides, increasing at an exponential rate, is becoming a global problem and leading to an urgent demand of developing novel compounds against both resistant and wild AHAS. In the present work, a series of novel 2-aroxyl-1,2,4-triazolopyrimidine derivatives (a total of 55) were designed and synthesized with the aim ...