Saccharothrixones A–D, Tetracenomycin-Type Polyketides from the Marine-Derived Actinomycete Saccharothrix sp. 10-10

Saccharothrixones A–C (1–3), three new aromatic polyketide seco-tetracenomycins, and saccharothrixone D (4), a new tetracenomycin analogue possessing opposite configurations at all of the stereogenic centers, were isolated from the marine-derived actinomycete Saccharothrix sp. 10-10. Compounds 1–3 represent the first examples of seco-tetracenomycins where the quinone ring B is cleaved and re-formed into a furanone ring. Their structures were elucidated by spectroscopic analyses and ECD calculations. The absolute configuration of 4 was confirmed by single-crystal X-ray diffraction analysis. Saccharothrixone D (4) showed in vitro cytotoxic activity against the HepG2 cancer cell line with an IC50 value of 7.5 μM.