Effect of substituents at phenyl group of 7,7′-dioxo-9,9′-epoxylignane on antifungal activity

Structure-Antifungal Activity Relationship of Fluorinated Dihydroguaiaretic Acid Derivatives and Preventive Activity against Alternaria alternata Japanese Pear Pathotype

The structure-activity relationship of the antifungal fluorinated dihydroguaiaretic acid derivatives was evaluated. Some of the newly synthesized lignan compounds were found to show higher antifungal activity against phytopathogenic fungi such as Alternaria alternata (Japanese pear and apple pathotypes) and A. citri than the lead compound, 3-fluoro-3'-methoxylignan-4'-ol (3). The broad antifungal spectrum of 3'-hydroxyphenyl derivative 16 was observed, and the 3'-fluoro-4'-hydroxyphenyl derivative 38 was found to show the highest activity against the A. alternata Japanese pear pathotype, with an EC₅₀ value of 11 μM. The preventive effect of the potent lignan on the infection of A. alternata in the Japanese pear's leaves was also shown.

Structure-plant growth inhibitory activity relationship of lariciresinol

The syntheses of 55 lariciresinol derivatives containing derivatives on the 9-position and an aryl group at both 7- and 7'-positions were successful to examine the effect of structure of (-)-lariciresinol (1) on plant growth regulatory activity. (-)-(7R,8R,8'S)-9-Dehydroxylariciresinol 9 showed activity 2-fold more potent than that of natural (-)-lariciresinol (1) and -95% growth inhibitory activity to negative control against rye grass root at 1 mM. The derivatives bearing hydrophobic and smaller groups at the 9-position showed higher activity. The importance of 4- and 4'-hydroxy groups and 3- and 3'-small hydrophobic groups on 7- and 7'-phenyl groups for higher activity was also suggested.

Quantitative structure-activity relationship analysis of antifungal (+)-dihydroguaiaretic acid using 7-phenyl derivatives

The relationship between antifungal activity against Alternaria alternata and structure on the 7-phenyl group of (+)-dihydroguaiaretic acid ((+)-DGA) was clarified by employing 38 synthesized (+)-DGA derivatives. The results were identified by quantitative structure-activity relationship (QSAR) analysis employing the Hansch-Fujita method. Some compounds showed higher activity than (+)-DGA. The compound showing highest activity was 3,5-difluorophenyl derivative 37. It was suggested that the small electron-withdrawing group at the meta-position of the 7-phenyl group is important for the higher activity by antifungal test and Hansch-Fujita analysis. The whitening activity of 3-hydroxy-4-methoxyphenyl derivative 28, 3-hydroxy-4-ethoxyphenyl derivative 29, and 3-hydroxy-4-isopropoxyphenyl derivative 30 against A. alternata Japanese pear pathotype was also discovered.

First discovery of insecticidal activity of 9,9'-epoxylignane and dihydroguaiaretic acid against houseflies and the structure-activity relationship

The insecticidal activity of (-)-(8R,8'R)-3,3'-dimethoxy-9,9'-epoxylignane-4,4'-diol (1) against houseflies was clarified for the first time. The activities of other stereoisomers were weaker than that of the (8R,8'R)-stereoisomer. In the course of research into structure-activity relationships involving 30 newly synthesized (8R,8'R)-derivatives, 5-fold higher activity (ED50 = 0.91 nmol/fly) was observed for (-)-(8R,8'R)-3,3',4-trimethoxy-9,9'-epoxylignan-4'-ol (21) than for the naturally occurring compound (1). The activity of 1 was weaker than that of (-)-(8R,8'R)-dihydroguaiaretic acid ((-)-DGA) (4); however, compound 21 showed almost the same level of activity as 4.