Pentaketides and 5--Hydroxyphenyl-2-pyridone Derivative from the Culture Extract of a Marine Sponge-Associated Fungus KUFA0732.

Five undescribed pentaketide derivatives, ()-6,8-dihydroxy-4,5-dimethyl-3-methylidene-3,4-dihydro-1-2-benzopyran-1-one (), [(3,4)-3,8-dihydroxy-6-methoxy-4,5-dimethyl-1-oxo-3,4-dihydro-1-isochromen-3-yl]methyl acetate (), ()-5, 7-dimethoxy-3-((-(1-hydroxyethyl)-3,4-dimethylisobenzofuran-1(3)-one (), ()-7-hydroxy-3-(()-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran 1(3)-one (), and a -hydroxyphenyl-2-pyridone derivative, avellaneanone (), were isolated together with the previously reported ()-3-acetyl-7-hydroxy-5-methoxy-3,4-dimethylisobenzofuran-1(3)-one (), ()-7-hydroxy-3-(()-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran-1(3)-one () and isosclerone (), from the ethyl acetate extract of a culture of a marine sponge-derived fungus, KUFA0732. The structures of the undescribed compounds were elucidated using 1D and 2D NMR, as well as high-resolution mass spectral analyses. The absolute configurations of the stereogenic carbons in , , , and were established by X-ray crystallographic analysis. The absolute configurations of C-3 and C-4 in were determined by ROESY correlations and on the basis of their common biosynthetic origin with . The crude fungal extract and the isolated compounds , , , , and were assayed for their growth inhibitory activity against various plant pathogenic fungi viz. , , , , , , , , and .