| Summary: | Two fenclorim derivatives (compounds <b>6</b> and <b>7</b>) were synthesized by linking active sub-structures using fenclorim as the lead compound. The chemical structures of the two compounds were confirmed by NMR spectroscopy, high resolution mass spectrometry, and X-ray diffraction analysis. Their fungicidal activity against six plant fungal strains was tested. Compounds <b>6</b> and <b>7</b> both crystallized in the monoclinic system, with a P2<sub>1</sub>/c space group (a = 8.4842(6) Å, b = 24.457(2) Å, c = 8.9940(6) Å, V = 1855.0(2) Å<sup>3</sup>, Z = 4) and Cc space group (a = 10.2347(7) Å, b = 18.3224(10) Å, c = 7.2447(4) Å, V = 1357.50(14) Å<sup>3</sup>, Z = 4), respectively. The crystal structure of compound <b>6</b> was stabilized by C–H···N and C–H···O hydrogen bonding interactions and N–H···N hydrogen bonds linked the neighboring molecules of compound <b>7</b> to form a three-dimensional framework. Compound 6 displayed the most excellent activity, which is much better than that of pyrimethanil against <i>Botrytis cinerea</i> in vivo. Additionally, compound 6 exhibited greater in vitro activity against <i>Pseudoperonospora cubensis</i> compared to that of pyrimethanil. Moreover, compound <b>7</b> exhibited strong fungicidal activity against <i>Erysiphe cichoracearum</i> at 50 mg/L in vitro, while pyrimethanil did not. Compounds <b>6</b> and <b>7</b> could be used as new pyrimidine fungicides in the future.
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