Synthesis of novel 18-glycyrrhetinic acid sulfonate derivatives displaying significant anti-oomycete activity against .

Using 18-glycyrrhetinic acid (GA) as the lead compound, fourteen GA sulphonate derivatives (-) were prepared by modifying its C-3 OH group, and their structures were well confirmed by H NMR, C NMR, HRMS and melting points. Moreover, we screened the anti-oomycete activity of these compounds against by using the mycelial growth rate method. Among the fourteen GA sulphonate derivatives evaluated, four compounds , , and exhibited more potent anti-oomycete activity than that of the positive control zoxamide (EC = 25.17 mg/L), and had the median effective concentration (EC) values of 23.04, 16.16, 22.55, and 13.93 mg/L, respectively. Especially compound showed the best anti-oomycete activity against with EC value of 13.93 mg/L. Overall, the introduction of sulfonyloxy groups at the C-3 position of GA has a significant impact on its anti-oomycete activity, and the corresponding derivative activity varies significantly with different substituents R.