Synthesis and antifungal activities of novel nicotinamide derivatives containing 1,3,4-oxadiazole

BACKGROUND Pant diseases in agriculture are extremely difficult to control, which bring about for billions of dollars in economic losses worldwide each year; Nicotinamide derivatives has attracted more and more attention in the field of pesticide due to their broad bioactivities. In an effort to discover new molecules with good antifungal activity, a series of nicotinamide derivatives containing 1,3,4-oxadiazole were synthesized and bio-assayed. RESULTS Bioassays demonstrated that some of the title compounds exhibited favorable antifungal activities against Gibberella zeae, Fusarium oxysporum, and Cytospora mandshurica. compounds 7b, 7c, 8, 9a, 9b, and 9c displayed 46.4%, 39.6%, 53.0%, 43.2%, 58.3%, 45.6% activities against G. Zeae, respectively; the activities of compounds 7a, 7b, 8, 9a, 9b, and 9c against F. oxysporum were 55.2%, 51.1%, 58.9%, 63.2%, 53.3%, and 47.6%, respectively; whereas inhibitory rates of compounds 7a, 7b, 7c, 8, 9a, 9b, and 9c on C. mandshurica were 53.1%, 49.9%, 44.9%, 52.8%, 59.8%, 54.5%, and 49.3%, respectively. CONCLUSION A series of the novel nicotinamide derivatives containing 1,3,4-oxadiazole were synthesized and bio-assayed. The results of antifungal tests revealed that the synthesized nicotinamide derivatives possessed weakly to moderately antifungal activities against G. zeae, F. oxysporum, and C. mandshurica. Most of the synthesized compounds exhibited similar activities as (or higher than) these of hymexozol on their corresponding fungus, and compounds 7a, 8, 9a, and 9b showed considerable prospects for further optimization. Primary structure-activity relationships revealed that the introduction of the groups of 4-chloro-6-methyl on benzene, the hydrazone group containing N,N-dimethylamino, and acetyl at -NH2 could enhance the antifungal activity.