Synthesis of Novel Pyrimidinylselenium Compounds as Acetolactate Synthase‐Inhibiting Herbicides

Abstract

AbstractA series of pyrimidinylselenosalicylic acid derivatives (5 a–5 l) and 4‐selenopyrimidine derivatives (6 a–6 f) were synthesized and evaluated as potential acetylactate synthase (ALS)‐inhibiting herbicides. All synthesized new compounds were characterized by 1H NMR, 13C NMR, and high‐resolution mass spectrometry (HRMS). The compounds were subjected to herbicidal activity, in vitro ALS enzyme inhibitory activity, and crop safety studies. The herbicidal activity study shows that 4‐chloro (5 b), 5‐chloro (5 c), 5‐methoxy (5 e), 4,5‐dimethoxy (5 f), 5‐fluoro (5 h), and 4,5‐difluoro (5 i) substituted 2‐[(4,6‐dimethoxy‐2‐pyrimidinyl)selanyl]benzoic acid exhibit significantly enhanced weed control effect than other new compounds and Pyrithiobac. Most of compounds exhibit enhanced inhibition effect on Cyperus difformis Linn than those on barnyard grass, Portulaca oleracea, Eleusine indica, and Amaranthus retroflexus. Importantly, 5 c, 5 f, and 5 i also exhibit more potent inhibition effect on Escherichia coli ALS enzyme than other new compounds and Pyrithiobac in in vitro ALS enzyme inhibitory activity study. The possible binding modes of 5 c, 5 f, and 5 i with ALS enzyme were studied on Discovery Studio. To test the possibility of 5 c, 5 f, and 5 i as potential herbicides in paddy fields, we performed the crop safety study. The results show that 5 f and 5 i are safer to rice than 5 c. The present work indicates that 5 f and 5 i may serve as new herbicide candidates for weed control in paddy fields.