| Summary: | 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 <sup>1</sup>H-NMR, <sup>13</sup>C-NMR, FTIR and HR-MS spectra. The single-crystal structures of compounds <b>4e</b>, <b>4h</b>, <b>5h</b> and <b>6c</b> were further confirmed using X-ray diffraction. The antifungal activities against <i>Botrytis cinerea</i> (<i>B. cinerea</i>), <i>Alternaria</i><i>solani</i> (<i>A. solani</i>), <i>Gibberella zeae</i> (<i>G. zeae</i>), <i>Rhizoctorzia solani</i> (<i>R. solani</i>), <i>Colletotrichum orbiculare</i> (<i>C. orbiculare</i>) and <i>Alternaria alternata</i> (<i>A. alternata</i>) 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 <b>5f</b> and <b>6h</b> exhibited outstanding antifungal activity against <i>B. cinerea</i> 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 <b>5f</b> was identified as the promising fungicide candidate against <i>B. cinerea</i> with the EC<sub>50</sub> 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 <b>5f</b> showed remarkable antifungal activities against <i>R. solani</i> with the EC<sub>50</sub> 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.
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