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The unique structural features of the succinate dehydrogenase inhibitor (SDHI) isoflucypram ( 1 ), the N -cyclopropyl substituent and the C 1-linker between phenyl and carboxamide function, lead to the creation of an individual SDHI subgroup by Fungicide Resistance Action Committee (FRAC), the N -cyclopropyl- N -benzyl-pyrazole-carboxamides. The combination of those structural elements is key for the excellent in vitro as well as in vivo efficacy of ( 1 ). The slightest variations of the N -cyclopropyl substituent lead to significantly lower efficacy. The chemical discovery of isoflucypram began with a combination of chemical motifs known from herbicidal and insecticidal structures, followed by applying stereoisomerism and mix and match principles, which led to the discovery of the fungicidal N -cyclopropyl-acyl-sulfonamide ( 5 ). Further downstream optimization led finally to the invention of isoflucypram ( 1 ). Isoflucypram ( 1 ) has been selected out of several potential development candidates from its chemical class based on its excellent safety profile, specifically in relation to endocrine-disrupting behavior. The active ingredient can be synthesized in a three-step synthesis starting from 2-bromo-4-chloro-cumol. Isoflucypram controls a diverse range of ascomycetes and basidiomycetes. ( 1 ) has a specific strength against all major leaf diseases in cereals, but ( 1 ) is also effective against key diseases in the horticulture segment, like grey mould, black sigatoka, and mildews. Cross-resistance studies suggest a partly incomplete cross-resistance pattern of isoflucypram, fluopyram, and other SDHIs, leading to the conclusion that isoflucypram exhibits a unique cross-resistance profile