New antifungal cycloheximide epimers produced by Streptomyces sp. YG7

A couple of new cycloheximide epimers, 13(α)-acetoxy-anhydroisoheximide (1) and 13(β)-acetoxy-anhydroisoheximide (2), together with six known compounds (3–8), were obtained from the cultures of Streptomyces sp. YG7. The structures were elucidated based on a comprehensive spectroscopic data analysis including 1D and 2D NMR, as well as HRESIMS, and by comparison with the literature. The X-ray crystal analysis of 1 further confirmed the structure. All the compounds were tested for antifungal activity. Compounds 1, 2 and 5–8 showed moderate Canidia albicans inhibitory activity, while 5 and 6 presented moderate Pyricularia oryzae inhibitory activity.