Synthesis and biological profiling of half-calycanthaceous alkaloid analogues.

During our continuous efforts to pursue antifungal agents, some calycanthaceous alkaloid analogs showed diverse and promising bioactivities. Therefore, 34 new calycanthaceous alkaloid derivatives were further prepared and screened for bioactivities. As a result of the evaluation against a great deal of plant pathogen fungi, bacteria and human pathogenic fungi, a majority of them displayed potent bioactivity. In particular, compound b6 displayed remarkably activity and might be novel potential leading compound for further development of antifungal agent. The relationship between structure and biological activity was also discussed.

Synthesis and fungicidal activity of tryptophan analogues - the unexpected calycanthaceous alkaloid derivatives.

A series of 21 N-protected tryptophan derivatives were synthesised from tryptophan in good yields. Their structures were characterised by IR, 1H NMR, 13C NMR, DEPT (90° and 135°) and MS analysis. The synthesised compounds were evaluated against a wide variety of plant pathogen fungi. Compounds a19 and a21 displayed activity against Fusarium oxysporum (F. oxysporum), and compound a21 showed high activity against F. oxysporum and Eggplant Verticillium, with EC50 values of 58.27 and 77.39 µg mL-1, respectively. Considering that the bioassay of the title compounds was evaluated, effects of the chain alkyl substituents may contribute to the significant variations in fungicidal potency. Their structure-antifungal activity relationships were also discussed. These results will pave the way for further design, structural modification and development of calycanthaceous alkaloids as antimicrobial agents.