Two new polyketides from the ascomycete fungus Leptosphaeria sp

Leptosphaerins H and I (1 and 2), two new xanthone derivatives, and six known compounds, leptosphaerin F (3), monodictysin B (4), norlichexanthone (5), leptosphaerin D (6), moniliphenone (7) and emodinbianthrone (8) have been isolated from a scale-up fermentation of the ascomycete fungus Leptosphaeria sp. Their structures were primarily elucidated by interpretation of NMR spectroscopic data. The absolute configuration of 1 was assigned using the modified Mosher method, whereas that of C-8a in 2 was determined via the CD data. Compound 6 showed modest cytotoxicity against a panel of three human tumor cell lines.