Oxalactam A, a Novel Macrolactam with Potent Anti- Activity from the Endophytic Fungus .

A novel macrolactam named oxalactam A (), three known dipeptides (-) as well as other known alkaloids (-) were obtained from the endophytic fungus , which was derived from the tuber of (Icacinaceae). All chemical structures were established based on spectroscopic data, chemical methods, ECD calculations, and C-DP4+ analysis. Among them, oxalactam A () is a 16-membered polyenic macrolactam bearing a new skeleton of 2,9-dimethyl-azacyclohexadecane core and exhibited potent anti- activity with a MIC value of 10 μg/mL in vitro. The plausible biosynthetic pathway of was also proposed via the alanyl protecting mechanism. Notably, three dipeptides (-) were first identified from the endophytic fungus and the NMR data of cyclo(-Trp--Glu) () was reported for the first time. In addition, the binding interactions between compound and the sterol 14-demethylase enzyme (CYP51) were studied by molecular docking and dynamics technologies, and the results revealed that the 16-membered polyenic macrolactam could be a promising CYP51 inhibitor to develop as a new anti- fungicide.