Synthesis and Antifungal Activity of New 3,4,7-Trisubstituted Coumarins

Fifty-three new 3-(2-diethylaminoethyl)-4-methyl-7-substituted coumarins were synthesized by four different routes utilizing commercially available 3-(2-diethylaminoethyl)-7-hydroxy-4-methylcoumarin hydrochloride. Their antifungal activities were measured against a phytopathologic fungi, Botrytis cinerea. Some compounds with a substituted benzoyloxy, benzoyloxyethoxy, methylbenzoylaminoethoxy, or benzoylaminophenoxy group at the 7-position had an inhibitory effect (MIC: <50 ppm) on the germination of spores in an in vitro screening system. Among them, eight derivatives had interest activities. The highest level of activity (MIC: 7.8 ppm) was observed for the coumarin with a 7-[4-(2,4,6-trichlorobenzoylamino) phenoxy] substitution. This derivative also inhibited the germination of four other plant pathogens, Colletotrichum orbiculare, Alternaria mali, Phytophthora capsici, and Pyricularia oryzae.