Synthesis, anti-oomycete activity of 1-sulfonyloxy/acyloxysesamol derivatives

Abstract

In order to explore novel natural product-based anti-oomycete agent, sixteen 1-sulfonyloxysesamol derivatives (3a-p) and fourteen 1-acyloxysesamol derivatives (5a-n) were designed and prepared, and structurally confirmed by 1H NMR, 13C NMR, HRMS, and melting point. The stereochemical configurations of compounds 3k and 5f were unambiguously confirmed by single-crystal X-ray diffraction. Moreover, we assessed the target compounds 3a-p and 5a-n as anti-oomycete activity against a serious agricultural disease of Phytophthora capsici by using the mycelial growth rate method. Among the thirty sesamol ester derivatives determined, eight compounds 3j, 3k, 3m, 3p, 5g, 5i, 5l, and 5m showed more potent anti-oomycete activity than that of the positive control zoxamide (EC50 = 23.79 mg/L), and the EC50 values of 13.80, 17.65, 11.80, 12.70, 17.71, 9.53, 21.94, and 15.43 mg/L, respectively. Especially compound 5i exhibited the best anti-oomycete activity against P. capsici with EC50 value of 9.53 mg/L. Overall, the anti-oomycete activities of 1-acyloxysesamol derivatives is higher than that of 1-sulfonyloxysesamol derivatives. It is proved that the introduction of the acyl group at hydroxyl position of sesamol is more beneficial to improve its anti-oomycete activity than that of the sulfonyl group.