New Pyran‐2‐ones from Alkalophilic Actinomycete, Nocardiopsis alkaliphila sp. Nov. YIM‐80379

Two new pyran-2-ones, nocardiopyrones A and B (1 and 2, resp.), along with four known compounds, pyridinols 3–5, and 1-acetyl-β-carboline (6) were isolated from the alkalophilic actinomycete Nocardiopsis alkaliphila sp. nov. YIM-80379. Their structures were established on the basis of spectroscopic analysis, CD spectra, and the quantum-chemical ECD calculation. Pyridinols 3–5 were isolated from a natural source for the first time. Compounds 1 and 2 showed weak antibacterial activities against Pseudomonas aeruginosa, Enterobacter aerogenes, and Escherichia coli with MIC values of 20–48 μM. Compound 2 showed weak antimicrobial activities against Candida albicans and Staphylococcus aureus with MIC values of 24 and 48 μM, respectively.