Regiospecific and Enantiospecific Effects of the β-Benzyl-α-benzylidene-γ-butyrolactone Structure on Phytotoxic Fungi

Abstract

Novel derivatives of E-β-benzyl-α-benzylidene-γ-butyrolactone (3-benzyl-2-benzylidene-4-butanolide) with lignano-9,9′-lactone structures were developed as anti-phytopathogenic fungal compounds. Their regiospecific and enantiospecific characteristics were determined, with the E-form and 3R-configuration showing higher activities against the Alternaria alternata Japanese pear pathotype. By the syntheses of benzyl compounds instead of benzylidene and aromatic derivatives, followed by an bioassay experiment, the importance of the benzylidene structure and effects of the substituents of the aromatic ring were clarified. The (2-OCH 3 , 4′-CH 3 /4′-CF 3 )-derivatives, 19 and 25, and (2-OCH 3 , 6-CH 3 /6-F/6-Br, 4′-OCH 3 )-derivatives, 34, 38, and 42, were more effective with EC 50 values of 0.1−0.3 μM. It was assumed that the 2-OCH 3 group, a hydrophobic group at the 6-position, and some size of the hydrophobic group at the 4′-position were necessary for the increased activity.