Design, synthesis and antifungal activities of novel cis-enamides via intermediate derivatization method

On the basis of the structure of natural product lansiumamide B (1), a total of 27 novel cis-enamide compounds were designed and synthesized via Intermediate Derivatization Method. Their chemical structures were characterized by ¹H and ¹³C nuclear magnetic resonance and high-resolution mass spectrometry. The in vitro antifungal activities against Sclerotinia sclerotiorum, Thanatephorus cucumeris and Botrytis cinerea were evaluated by the mycelium linear growth rate method. Most of the compounds showed some activity against each of the fungi at 25 or 50 μg/mL. The relationship between structure and antifungal activity was also discussed, which showed the cinnamic double bond was critical to maintain the antifungal activity. Notably, among the title compounds, 3e and 3h could inhibit mycelia growth of Botrytis cinerea by approximately 50% (EC₅₀) at 39.17 and 41.25 μg/mL respectively, which showed better antifungal activity than lansiumamide B (1) with more concise chemical structure. The present study pointed out the correct direction for the development and optimization of lansiumamide B derivatives as potential inhibitors of pathogenic fungi.