Synthesis and antifungal activity of hinokitiol derivatives

Seventeen novel derivatives of hinokitiol, a monoterpene with a troponoide skeleton, were designed and synthesized. Their structures were confirmed by NMR and HRMS. The in vitro bioassay results showed that the target compounds displayed satisfactory antifungal activities against Rhizoctonia solani, Botrytis cinerea, Sclerotinia sclerotiorum, Valsa mali and Colletotrichum orbiculare at 50 μg/mL. Notably, compound 3a showed favorable activity against R. solani (EC₅₀ = 1.84 μg/mL), 3j exhibited satisfied activity against B. cinerea (EC₅₀ = 2.47 μg/mL), and 3m exerted excellent activity against S. sclerotiorum (EC₅₀ = 1.05 μg/mL), which are better than hinokitiol (2.00, 11.3 and 5.40 μg/mL).