Synthesis and biological evaluations of a series of calycanthaceous analogues as antifungal agents.

Starting from indole-3-acetonitrile, a total of 66 new calycanthaceous alkaloid analogues were synthesised in excellent yields. The prepared compounds were evaluated for their biological activities against a broad range of plant pathogen fungi. The results of bioassays indicated that the majority of tested compounds displayed comparable or better in vitro bioactivities than the positive control. Notably, Compound a1 displayed a significant activities against B. cereus, Escherichia sp and R. solanacearum, even better than the positive control streptomycin and Penicillin, with the same MIC value of 15.63 µg mL-1. Compound a1 displayed a broad spectrum and remarkably activities among the tested calycanthaceous analogues and might be a novel potential leading compound for further development of antifungal agents. The results obtained in the study will be very helpful for further design and structural optimisation of calycanthaceous alkaloids as potential agrochemical lead for plant disease control.