(±)-Eurotone A [(±)- 1 ], a pair of new enantiomeric polyketide dimers, as well as six known biogenetically related polyketides ( 2 – 7 ) were isolated from a marine-derived fungus Eurotium sp. SCSIO F452. Their structures were determined by comprehensive spectroscopic methods, X-ray diffraction and quantum chemical calculations. Compound 1 represented the first pair of spirodihydrobenzanthracene enantiomers isolated from marine fungi with their absolute configurations assigned. A plausible biosynthetic pathway involving a key acid-mediated dimerization was proposed for 1 . The antioxidative activities of the new enantiomers were evaluated.
