Synthesis and antifungal activity of norbornene derivatives containing thiourea group

To explore more potential fungicides with new scaffolds, 10 norbornene derivatives containing thiourea group were designed, synthesized and assayed for inhibitory activity against three plant pathogenic fungi. The preliminary antifungal assay suggested that the title derivatives showed moderate to good antifungal activity against six plant pathogens. Especially, norbornene derivatives 3g presented excellent in vitro antifungal activity against Botryosphaeria dothidea (EC 50 = 9.51 mg/L), which was approached to chlorthalonil. In vivo antifungal assay indicated norbornene derivatives 3g displayed excellent protective and curative effects on apple fruits infected by B. dothidea. The preliminary mechanism study displayed that norbornene derivatives 3g could damage the surface morphology. In addition, the phytotoxicity test revealed norbornene derivatives 3g showed safety on seeds of mung bean. The bioassay results and mechanism investigation demonstrated that this class of norbornene derivatives containing thiourea group could be promising fungicide for further development.