Lead discovery and molecular target identification are
important
for developing novel pesticides. Scaffold hopping, an effective approach
of modern medicinal and agrochemical chemistry for a rational design
of target molecules, is aiming to design novel molecules with similar
structures and similar/better biological performance. Herein, 24 new
ferimzone derivatives were designed and synthesized by a scaffold-hopping
strategy. In vitro bioassays indicated that compound 5o showed similar potency to ferimzone against Cercospora arachidicola and 2-fold higher potency than ferimzone against Alternaria
solani. Compounds 5q, 6a, and 6d displayed fungicidal activity with EC50 values
ranging from 1.17 to 3.84 μg/mL against Rhizoctonia
solani, and compounds 5q and 6a displayed 1.6–1.8-fold higher activity than ferimzone against Fusarium graminearum. The in vivo bioassays at 200 μg/mL
indicated that compound 5q was more potent than ferimzone
against Pyricularia oryzae (90% vs 70% efficacy,
respectively). Density functional theory (DFT) calculations elucidated
the structure–energy relationship. Although the mode of action
of ferimzone is still unclear, studies suggested that compound 5q significantly inhibited the growth and reproduction of R. solani, and its energy metabolism pathways (e.g., starch,
sucrose, lipids, and glutathione) were seriously downregulated after
a 5q treatment.