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Late blight in potatoes and downy mildew in fruit vegetables are among the important diseases that have negative effects on the yield and quality of products, both at home and abroad. These diseases spread rapidly and cannot be controlled only by preventive application, which calls for the development of fungicides that also have a curative effect. Benthiavalicarbisopropyl is a novel fungicide belonging to the carboxylic acid amides (CAA) group. This compound is a highly selective fungicide that is effective against late blight and downy mildew caused by plant pathogens that belong to Oomycetes. A series of new fungicides with high preventive effect against late blight and downy mildew have recently been developed; however, few of them possess the curative effect desired by users. Benthiavalicarb-isopropyl has not only a superb preventive, but also a superb curative effect against these diseases; it also has a favorable environmental, ecotoxicological and toxicological profile. At present, benthiavalicarb-isopropyl is registered as an agrochemical in 21 countries, including Japan. This paper describes the history of the discovery, synthesis, structure-activity relationships, biological activities and safety of benthiavalicarb-isopropyl. Discovery and SynthesisDuring the investigation of a novel fungicide that is active against late blight and downy mildew, we studied carbamate derivatives in the patent with N-phenethylvalinamide moiety in the molecule. To the best of our knowledge, they showed activity against late blight and downy mildew but were not vital as fungicides. We applied biological equivalence, introducing a benzofuran ring in place of a benzene ring of the phenethyl group in order to find a novel lead compound showing fungitoxic activity. The fungitoxic activity of the benzofuran-introduced carbamate surpassed that of the carbamate derivatives in the patent. We then studied the structural modification of the benzofuran-introduced carbamate as a lead compound. Structural optimization of the lead compound was per- Benthiavalicarb-isopropyl is a novel fungicide belonged to the carboxylic acid amides (CAA) group. This compound is a highly selective fungicide that has superb preventive and curative effects on late blight and downy mildew caused by plant pathogens that belong to Oomycetes. Benthiavalicarb-isopropyl strongly inhibits mycelia growth, zoosporangia germination and cystospore germination, and also inhibits the sporulation of Phytophthora infestans at a very low concentration. The fungicidal and disease-controlling activities of benthiavalicarb-isopropyl are characterized by its excellent preventive, curative, translaminar, systemic movement, residual activities, its inhibitory activity toward lesion development and its rain fastness. These results suggest that the biological properties of benthiavalicarb-isopropyl contribute to its excellent ability to control several diseases in the field. Development of a new fungicide, benthiavalicarb-isopropyl*

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