Dimeric Tetrahydroanthracene Regioisomers and Their Monomeric Precursor Produced by Streptomyces fumigatiscleroticus HDN10255

Four new tetrahydroanthracene derivatives (1, 3-5) and a known antibiotic, A-39183A (2), were discovered from the marine-sponge-derived actinomycete Streptomyces fumigatiscleroticus HDN10255. Their structures including absolute configurations were elucidated based upon MS and NMR spectroscopic data, ECD calculations, and biogenetic considerations. Compounds 2 and 4 showed considerable cytotoxicity with the best IC50 value of 1.8 μM against HeLa cells.