Synthesis of novel 18 β -glycyrrhetinic acid sulfonate derivatives displaying significant anti-oomycete activity against Phytophthora capsici

AbstractUsing 18β-glycyrrhetinic acid (GA) as the lead compound, fourteen GA sulphonate derivatives (3a–n) were prepared by modifying its C-3 OH group, and their structures were well confirmed by 1H NMR, 13C NMR, HRMS and melting points. Moreover, we screened the anti-oomycete activity of these compounds against Phytophthora capsici by using the mycelial growth rate method. Among the fourteen GA sulphonate derivatives evaluated, four compounds 3f, 3j, 3k and 3l exhibited more potent anti-oomycete activity than that of the positive control zoxamide (EC50 = 25.17 mg/L), and had the median effective concentration (EC50) values of 23.04, 16.16, 22.55, and 13.93 mg/L, respectively. Especially compound 3l showed the best anti-oomycete activity against P. capsici with EC50 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.Keywords: Natural product18β-glycyrrhetinic acidsulfonylationanti-oomycete activityphytophthora capsici Disclosure statementNo potential conflict of interest was reported by the author(s).Additional informationFundingThis work was financially supported by the National Natural Science Foundation of China [Grant No. 31901863 and 32102249], Young Teacher Funding Program of the Henan Higher School [Grant No. 2020GGJS080], Key Science and Technology Program of Henan Province [Grant No. 222102110023], Heluo Youth Talent Project [Grant No. 2023HLTJ01].