Design, synthesis and antifungal activity of amide and imine derivatives containing a kakuol moiety.

In continuation of our program to discover new potential antifungal agents, a series of amide and imine derivatives containing a kakuol moiety were synthesized and characterized by the spectroscopic analysis. By using the mycelium growth rate method, the target compounds were evaluated systematically for antifungal activities in vitro against four plant pathogenic fungi, and structure-activity relationships (SAR) were derived. Compounds 7d, 7e, 7h, 7i and 7r showed obvious inhibitory activity against the corresponding tested fungi at 50 µg/mL. Especially, compounds 7e and 7r displayed more potent antifungal activity against B. cinerea than that of thiabendazole (a positive control). Moreover, compound 7e also exhibited good activity against A. alternata with EC50 values of 11.0 µg/mL, and the value was slightly superior to that of thiabendazole (EC50 = 14.9 µg/mL). SAR analysis showed that the ether group was a highly sensitive structural moiety to the activity and the type as well as position of substituents on benzene ring could make some effects on the activity.