Bioisosteric Tactics in the Discovery of Tetflupyrolimet: A New Mode-of-Action Herbicide

The last new herbicidal modes-of-action with commercial significance were introduced to the marketplace multiple decades ago. Serious weed resistance to most herbicidal classes have since emerged with widespread use. Aryl pyrrolidinone anilides represent an entirely new mode-of-action class of herbicides that interfere with de novo pyrimidine biosynthesis in plants via inhibition of dihydroorotate dehydrogenase. The chemical lead for this new herbicide class discovery was identified from high-volume sourced greenhouse screening that required structural reassignment of the hit molecule followed by an extensive synthetic optimization effort. With excellent grass weed control and pronounced safety on rice, the selected commercial development candidate has a proposed common name of tetflupyrolimet and represents the first member of the new HRAC (Herbicide Resistance Action Committee) Group 28. This paper describes the discovery path to tetflupyrolimet with an added focus on the bioisosteric modifications pursued in optimization, including replacements of the lactam core itself.