Discovery of anti-phytopathogenic fungal activity of a new type of ()-coumarin bearing a phenylpropanoid unit at the 3-position.

The enantiospecific anti-phytopathogenic fungal activity of a new type of coumarin bearing a phenylpropanoid unit at the 3-position was found. ()-3-[1-Methoxy-3-(4-methoxyphenyl)prop-2-yl]coumarin (()-: EC=16.5 µM) was 30 times more effective than the ()-form against the Japanese pear pathotype. Derivatives bearing different substituents on the 7'-aromatic ring and the coumarin ring were synthesized to discover the more potent compounds. The 3'-CF and 4'-CF derivatives, and , respectively, had the lowest EC values (1-2 µM) in this project, suggesting that the size of the electron-withdrawing and hydrophobic substituents at these positions gave an advantage. On the coumarin ring, the presence of the OCH or CH group at the 5-position accelerated the activity, as the (4'-OCH, 5-OCH) derivative and (4'-OCH, 5-CH) derivative were, respectively, 4-5 times more potent than the 4'-OCH derivative ()-.