(+)- and (-)-Eurotone A: A pair of enantiomeric polyketide dimers from a marine-derived fungus Eurotium sp. SCSIO F452

(+/-)-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. (C) 2019 Published by Elsevier Ltd.