Design, synthesis, anti-oomycete, and anti-fungal activities of novel paeonol derivatives containing carbamate moiety.

Paeonol is the main active ingredient in the Chinese medicinal herb peony root bark. In order to discover new compounds with high efficiency and broad-spectrum pesticide biological activity, twenty novel paeonol carbamate derivatives (1a-c, 2a-c, 3a-c, 4a-c, 5a-c, and 1-5dd') were designed and synthesized by ingeniously introducing carbamate pharmacophores, and their structures were well characterized by 1H NMR, 13C NMR, and HRMS. The stereochemical configurations of two target compounds 2c and 3c were unambiguously subjected to single-crystal X-ray diffraction. Moreover, we evaluated the bioactivities of these target compounds as anti-oomycete and anti-fungal agents against two serious agricultural pathogens, Phytophthora capsici and Fusarium graminearum. Amongst evaluated compounds, (1) Seven target compounds 2a, 2b, 3b, 4b, 5a, 5b, and 5dd' exhibited good anti-oomycete against the plant pathogen P. capsici. (2) Three target compounds 5b, 5c, and 5d,d' displayed good anti-fungal against the plant pathogen F. graminearum. (3) When X = Y = Br and R1 = R2 = Et, the corresponding compound 5b exhibits the best anti-oomycete and anti-fungal activity, with EC50 values of 79.03 mg/L and 42.59 mg/L, respectively. Moreover, some interesting results of structure-activity relationships were also observed. This study provides valuable design ideas and theoretical data for further exploring the preparation and pesticide biological activity of paeonol carbamate derivatives.