Two bafilomycin derivatives with an unprecedented 6/5/5 tricyclic ring system (1 and 2), along with five known analogues (3–7), were identified from a marine Streptomyces sp. The structures of 1 and 2 were elucidated by analysis of HRESIMS, extensive NMR spectroscopic methods, GIAO DET ¹³C NMR calculations and comparison of the spectroscopic data with those of known related compounds. Compound 2 exhibited significant cytotoxicity against PC3 human prostate carcinoma cells with IC₅₀ value of 4.99 ± 0.15 μM.

中文翻译：

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具有海洋衍生链霉菌属物种的三环系统的细胞毒性bafilomycin类似物6/5/5

以前所未有的6/5/5三环系统（两个巴弗洛霉素衍生物1和2）中，用5个已知类似物（沿3 - 7），是从海洋鉴定链霉菌属。通过HRESIMS分析，广泛的NMR光谱方法，GIAO DET ¹³ C NMR计算以及光谱数据与已知相关化合物的比较，阐明了1和2的结构。化合物2对PC3人前列腺癌细胞表现出明显的细胞毒性，IC ₅₀值为4.99±0.15μM。