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

Five undescribed pentaketide derivatives, ( R )-6,8-dihydroxy-4,5-dimethyl-3-methylidene-3,4-dihydro-1 H -2-benzopyran-1-one ( 1 ), [(3 S ,4 R )-3,8-dihydroxy-6-methoxy-4,5-dimethyl-1-oxo-3,4-dihydro-1 H -isochromen-3-yl]methyl acetate ( 2 ), ( R )-5, 7-dimethoxy-3-(( S) -(1-hydroxyethyl)-3,4-dimethylisobenzofuran-1(3 H )-one ( 4b ), ( S )-7-hydroxy-3-(( S )-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran 1(3 H )-one ( 5 ), and a p -hydroxyphenyl-2-pyridone derivative, avellaneanone ( 6 ), were isolated together with the previously reported ( R )-3-acetyl-7-hydroxy-5-methoxy-3,4-dimethylisobenzofuran-1(3 H )-one ( 3 ), ( R )-7-hydroxy-3-(( S )-1-hydroxyethyl)-5-methoxy-3,4-dimethylisobenzofuran-1(3 H )-one ( 4a ) and isosclerone ( 7 ), from the ethyl acetate extract of a culture of a marine sponge-derived fungus, Hamigera avellanea 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 1 , 4b , 5 , and 6 were established by X-ray crystallographic analysis. The absolute configurations of C-3 and C-4 in 2 were determined by ROESY correlations and on the basis of their common biosynthetic origin with 1 . The crude fungal extract and the isolated compounds 1 , 3 , 4b , 5 , 6, and 7 were assayed for their growth inhibitory activity against various plant pathogenic fungi viz. Alternaria brassicicola , Bipolaris oryzae , Colletotrichum capsici, C. gloeosporiodes , Curvularia oryzae , Fusarium semitectum , Lasiodiplodia theobromae , Phytophthora palmivora , Pyricularia oryzae , Rhizoctonia oryzae and Sclerotium rolfsii .