Synthesis and Fungicidal Activity of α-Cyanoacetamide Derivatives: Discovery of a New Rice Blast Fungicide, Diclocymet (S-2900)

In order to search for a new systemic rice blast fungicide, a number of N-benzyl-α-cyanoacetamide derivatives and related compounds were prepared and their preventive activity against rice blast, Magnaporthe grisea was examined both in a foliar spray test and in a soil drench test. Several N-[1-(substituted-phenyl)ethyl]-2-cyano-3, 3-dimethyl-butanamides and -2-pentenamides showed high activity in both tests. Among them, (RS)-2-cyano-N-[(R)-1-(2, 4-dichlorophenyl)ethyl]-3, 3-dimethylbutyramide (diclocymet, S-2900) was selected as a practical new systemic rice blast fungicide, which shows potent fungicidal activity with little crop injury.