Synthesis, Anti‐Oomycete and Anti‐fungal Activities of Novel Cinchona Alkaloid Derivatives Containing Sulfonate Moiety

Abstract

AbstractUsing cinchona alkaloid as the lead compound, twenty‐four cinchona alkaloid sulfonate derivatives (1 a–l,2 a–c,3 a–c,4 a–c, and5 a–c) were designed and prepared by modifying their C9 position, and structurally confirmed by1H‐NMR,13C‐NMR, HR‐MS and melting points. Moreover, the stereochemical configurations of compounds1 fand1 lwere unambiguously confirmed by single‐crystal X‐ray diffraction. Furthermore, we determined the anti‐oomycete and anti‐fungal activities of these target compounds againstPhytophthora capsiciandFusarium graminearumin vitro. The results showed that two compounds4 band4 cexhibited prominent anti‐oomycete activity, and the median effective concentration (EC50) values of4 band4 cagainstP. capsiciwere 22.55 and 16.32 mg/L, respectively. This study suggested that when the C9 position of cinchona alkaloid sulfonate derivatives is in theSconfiguration and the 6′‐position methoxy group is not present, the anti‐oomycete activity is superior. In addition, five compounds1 e,1 f,1 k,3 cand4 cdisplayed significant anti‐fungal activity, with EC50values of 43.64, 45.07, 80.18, 48.58 and 41.88 mg/L againstF. graminearum, respectively. This result indicates that only when a specific substituent is introduced into the structural framework of the target compound, the corresponding compound exhibits significant inhibitory activity against fungi.