Ochuscins A-G, highly oxygenated usnic acid derivatives from the deep-sea-derived fungus Ochroconis sp. FS449

Ochuscins A-G (1-7), seven highly oxygenated usnic acid derivatives were isolated from the deep-sea-derived fungus Ochroconis sp. FS449. Their structures were elucidated based on the 1D, 2D NMR, HRE-SIMS and single crystal X-ray diffraction, while the absolute configurations were established by the quantum chemical calculations of C-13 NMR chemical shifts as well as ECD plots. The biosynthesis pathway of 1-7 was proposed to generate via a dimerization of phloroglucinol derivatives. In the bioassay, compounds 2, 3, 4 and 7 exhibited moderate inhibitory activities against acetylcholinesterase with the IC50 values in the range from 49 to 80 mu M. A preliminary structure-activity relationship was discussed. (C) 2020 Elsevier Ltd. All rights reserved.