Isoflucypram—the next-generation succinate dehydrogenase inhibitor fungicide

Isoflucypram (ISY) is a new, highly active succinate dehydrogenase inhibitor (SDHI) fungicide with two unique structural features. Herein the discovery and the optimization leading to ISY is described, an elegant combination of mix and match approaches with vast experience in SDHI chemistry. The unusual N-cyclopropyl substitution pattern for an SDHI suggests an altered binding of ISY to the ubiquinone binding site. Among many highly efficacious candidates ISY was selected based on its favorable human safety profile. ISY very efficiently controls all relevant leaf disease in cereals, namely, leaf blotch, net blotch, brown and yellow rust. The active translocates slowly but steadily in the cereal leaves, which contributes to a high extent to its long-lasting efficacy from the leaf base up to the leaf tip. ISY-based products have outcompeted in hundreds field trials current market standards regarding efficacy as well as even more importantly regarding yield.