Design, Synthesis, and Herbicidal Activity of Novel 5-Acylbarbituric Acid Derivatives Containing Maleimide Moieties and Evaluation of Their Mode of Action

In continuation of our search for herbicide lead compounds with novel structures and enhanced activities, a total of thirty 5-acylbarbituric acid derivatives containing maleimide moieties were designed and synthesized, and their herbicidal activities were evaluated in the greenhouse. The bioassay results showed that some of the newly synthesized target compounds had good herbicidal activity, of which <b>BT-IV-1</b> displayed an excellent inhibitory effect on <i>Brassia campestris</i>, <i>Amaranthus retroflexus</i>, <i>Amaranthus blitum</i>, <i>Chenopodium album</i>, <i>Portulaca oleracea</i>, and <i>Abutilon theophrasti</i>, with inhibition rate > 80% at the dosage of 37.5 g ha^-1, and it was determined to be safe for <i>Oryza sativa</i>, <i>Zea mays</i>, and <i>Panicum miliaceum</i> at the dosage of 75 g ha^-1. Studying the molecular mechanism by phenotypic observation, membrane permeability evaluation, molecular docking, and in vitro maize protoporphyrinogen oxidase (PPO) activity evaluation reveals that <b>BT-IV-1</b> is a PPO inhibitor. The present work indicates that <b>BT-IV-1</b> can serve as a potential lead compound for the further development of novel PPO-inhibiting herbicides.