Sparticolins A–G, Biologically Active Oxidized Spirodioxynaphthalene Derivatives from the Ascomycete Sparticola junci

To explore the chemical diversity of metabolites from new species of Dothideomycetes, the ex-type strain of Sparticola junciwas investigated. Seven highly oxygenated and functionalized spirodioxynaphthalene natural products incorporating carboxyalkylidene–cyclopentanoid (1–4), carboxyl-functionalized oxabicyclo[3.3.0]octane (5–6), and annelated 2-cyclopentenone/δ-lactone (7) units, sparticolins A–G, were isolated from submerged cultures of the fungus. Their chemical structures including their relative (and absolute) configurations were established through spectroscopic and X-ray crystallographic analyses. Sparticolin B (2) exhibited inhibitory activity against the Gram-positive bacteria Bacillus subtilis, Micrococcus luteus, and Staphylococcus aureus, while sparticolin G (7) showed antifungal activities against Schizosaccharomyces pombeand Mucor hiemalis. All other sparticolins were only weakly active against S. aureusand also showed weak activities against the nematode Caenorhabditis elegans. Compounds 2and 7also showed moderate cytotoxic activities against seven mammalian cell lines.