Novel Fluorinated 7-Hydroxycoumarin Derivatives Containing an Oxime Ether Moiety: Design, Synthesis, Crystal Structure and Biological Evaluation.

A series of fluorinated 7-hydroxycoumarin derivatives containing an oxime ether moiety have been designed, synthesized and evaluated for their antifungal activity. All the target compounds were determined by H-NMR, C-NMR, FTIR and HR-MS spectra. The single-crystal structures of compounds , , and were further confirmed using X-ray diffraction. The antifungal activities against (), (), (), (), () and () were evaluated in vitro. The preliminary bioassays showed that some of the designed compounds displayed the promising antifungal activities against the above tested fungi. Strikingly, the target compounds and exhibited outstanding antifungal activity against at 100 μg/mL, with the corresponding inhibition rates reached 90.1 and 85.0%, which were better than the positive control Osthole (83.6%) and Azoxystrobin (46.5%). The compound was identified as the promising fungicide candidate against with the EC values of 5.75 μg/mL, which was obviously better than Osthole (33.20 μg/mL) and Azoxystrobin (64.95 μg/mL). Meanwhile, the compound showed remarkable antifungal activities against with the EC values of 28.96 μg/mL, which was better than Osthole (67.18 μg/mL) and equivalent to Azoxystrobin (21.34 μg/mL). The results provide a significant foundation for the search of novel fluorinated 7-hydroxycoumarin derivatives with good antifungal activity.