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

Using 21 newly synthesized 7,7'-dioxo-9,9'-epoxylignane derivatives having a modified 7-phenyl group, we examined the relationship between their structure and antifungal activity against plant pathogens such as Bipolaris oryzae to determine the effects of various substituents on the antifungal activity. Compared with the lead compound having a 4-OH-3-CH(3)O-phenyl moiety, several analogs showed higher antifungal activity against B. oryzae, including the compound having an unsubstituted phenyl group and those having either of the following phenyl substituents: 2-OH, 4-CH(3)O, 4-C(2)H(5)O, 4-n-C(3)H(7)O, 4-n-C(4)H(9)O, 4-CF(3)O, 4-C(2)H(5), or 4-Cl.