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

Ten new tanzawaic acids, namely, steckwaic acids A-D (-), 11-ketotanzawaic acid D (), 6,15-dihydroxytanzawaic acid M (), 15-methoxytanzawaic acid M (), 15-methoxytanzawaic acid M (), 8-hydroxytanzawaic acid M (), and 8-hydroxytanzawaic acid B (), together with four known analogues (-), were isolated and identified from the endozoic fungus AS-324, which was obtained from a deep-sea sp. coral that was collected from the Magellan seamount in the Western Pacific Ocean. Structurally, steckwaic acids A-D (-) 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 , , and exhibited activities against aquatic pathogenic bacteria , , and with MICs of 2, 4, and 4 μg/mL, respectively.