Synthesis, antifungal activity, and 3d-QSAR study of L-carvone-based pyrazole-oxime ester compounds

Natural products can provide versatile substructures with potential bioactivity and biocompatibility for exploring bioactive compounds. Herein, to explore novel natural product-derived antifungal agents, 21 unreported L -carvone-based pyrazole-oxime ester compounds 6a-6u were synthesised using L-carvone as raw material, and structurally characterised by means of FT-IR,H-1 NMR,C-13 NMR, and HRMS. The results of the in vitro bioactivity tests showed that the target compounds exhibited certain antifungal activity against the eight tested plant fungi at the concentration of 50 mg/L, especially for Physalospora piricola. The inhibition rates of compounds 6e (R = m-Cl) and 6c (R = m-F) against P. piricola were 88.3% and 83.9%, respectively, both better than that of the positive control chlorothalonil. Compound 6e (R= m-Cl) with the most significant antifungal activity deserves further investigation as the potential leading compound. In addition, the structure-activity relationships (SARs) of the target compounds were investigated by establishing an effective three-dimensional quantitative structure-activity relationship (3D-QSAR) model.