Synthesis and antifungal/anti-oomycete activity of novel camphor-based sulfonate derivatives as potential SDH inhibitors

In this work, fourteen novel sulfonate derivatives 3a-3n bearing camphor scaffold were designed, synthesized and characterized by 1H-NMR, 13C-NMR, HR-MS and FT-IR spectra. The crystal structure of compound 3b was determined by X-ray diffraction analysis. In the preliminary antifungal activity bioassay, the title compounds presented moderate to prominent antifungal activity toward five crop pathogenic fungi and two crop pathogenic oomycetes. Among them, compound 3k exhibited prominent in vitro and in vivo antifungal activity toward P. capsici. The primary fungicide mechanism showed that 3k had a good capacity to destroy the surface morphology of P. capsici and interfere with the mycelial growth. Further, compound 3k exhibited potent SDH inhibitory activity with IC50 value of 0.66 µM, which was superior to carboxin (IC50 = 3.63 µM). Molecular docking results revealed that compound 3k well docked into the active site of SDH. These results indicated that compound 3k could be a novel monoterpene-derived SDHI inhibitor and is worthy of further study as a promising lead for fungicide development.