Oxalactam A, a Novel Macrolactam with Potent Anti- Rhizoctonia solani Activity from the Endophytic Fungus Penicillium oxalicum

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.