Sterol Biosynthesis Inhibitors

Fungicides that inhibit targets within the fungal sterol biosynthesis, known as sterol biosynthesis inhibitor (SBI) fungicides, have remained the most important group of specific fungicides worldwide over the last four decades. Among these, four classes can be outlined: demethylation inhibitor (DMI) fungicides, amine inhibitors of fungal Δ 14 -reductase and Δ 8 –Δ 7 -isomerase, 3-keto-reductase inhibitors (KRI), and inhibitors of squalene epoxidase. DMIs constitute the most economically significant mode-of-action class within SBI fungicides. While piperazines, pyrimidines, and imidazoles were the first of the DMI fungicides to enter the agricultural market, today still triazole fungicides drive the commercial success of DMIs. This area is still the subject of Research & Development across the industry, which recently resulted in the market introduction of a new azole and the announcement of several developmental compounds. Owing to resistance problems of cereal powdery mildew toward triazole fungicides during the mid-1980s, the amine inhibitors of Δ 14 -reductase and Δ 8 –Δ 7 -isomerase gained in importance as partners for the resistance management of triazole fungicides, since they show no cross-resistance to DMIs. Fungal squalene epoxidases are very distantly related to their mammalian and higher plant counterparts in the phylogenetic tree and their inhibitors have therefore mainly been developed as selective antimycotics and herbicides.