Uncommon Polyketides from Penicillium steckii AS-324, a Marine Endozoic Fungus Isolated from Deep-Sea Coral in the Magellan Seamount

Four unusual steckwaic acids E–H (1–4), possessing a rarely described acrylic acid unit at C-4 (1–3) or a double bond between C-12 and C-13 (4) are reported for the first time, along with four new analogues (5–8) and two known congeners (9 and 10). They were purified from the organic extract of Penicillium steckii AS-324, an endozoic fungus obtained from a deep-sea coral Acanthogorgiidae sp., which was collected from the Magellan Seamount at a depth of 1458 m. Their structures were determined by the interpretation of NMR and mass spectroscopic data. The relative and absolute configurations were determined by NOESY correlations, X-ray crystallographic analysis, and ECD calculations. All compounds were tested for their antimicrobial activities against human- and aquatic-pathogenic bacteria and plant-related pathogenic fungi.