Structurally diverse diketopiperazine alkaloids from the marine-derived fungus Aspergillus versicolor SCSIO 41016

摘要

Ten new diketopiperazine alkaloids (DAs, 1-10) along with two known congeners (11-12) were characterized from the marine sponge-derived fungus Aspergillus versicolor SCSIO 41016. Their structures including absolute configurations were determined by spectroscopic analyses, quantum chemical calculations, and X-ray diffraction analysis. Pyranamides A-D (1-4) were obtained as rare 1-oxa-8,10-diazaspiro[5.5]undecane containing diketopiperazine alkaloids, while secopyranamide C (5) was obtained as a tetrahydropyran-ring cleavage derivative. Plausible biosynthetic pathways of 1-12 were postulated. Compounds 7 and 12 exhibited weak cytotoxic activities against ACHN, OS-RC-2, and 786-O cells.