Tanzawaic Acid Derivatives: Fungal Polyketides from the Deep-Sea Coral-Derived Endozoic Penicillium steckii AS-324.

Ten new tanzawaic acids, namely, steckwaic acids A-D ( 1 - 4 ), 11-ketotanzawaic acid D ( 5 ), 6,15-dihydroxytanzawaic acid M ( 6 ), 15 R -methoxytanzawaic acid M ( 7 ), 15 S -methoxytanzawaic acid M ( 8 ), 8-hydroxytanzawaic acid M ( 9 ), and 8-hydroxytanzawaic acid B ( 10 ), together with four known analogues ( 11 - 14 ), were isolated and identified from the endozoic fungus Penicillium steckii AS-324, which was obtained from a deep-sea Acanthogorgiidae sp. coral that was collected from the Magellan seamount in the Western Pacific Ocean. Structurally, steckwaic acids A-D ( 1 - 4 ) represent the first tanzawaic acid derivatives containing a naphthalene ring. Their structures were elucidated by detailed interpretation of the NMR spectroscopic and mass spectrometric data. X-ray crystallographic analysis and ECD calculations confirmed their structures and absolute configurations. New compounds 1 , 5 , and 9 exhibited activities against aquatic pathogenic bacteria Micrococcus luteus , Vibrio anguillarum , and Pseudomonas aeruginosa with MICs of 2, 4, and 4 μg/mL, respectively.