Absolute configuration of cyclopropanes and the structural revision of pyrones from Marine-derived fungus Stagonospora sp. SYSU-MS7888

Abstract

Two new cyclopropane derivatives (1–2) and seven undescribed α-pyrone derivatives (3–9), along with one known congener (10) were obtained from the marine fungus Stagonospora sp. SYSU-MS7888, which was isolated from the South China Sea. Their planar structures were established through extensive spectroscopic analyses including 1D and 2D NMR and HR-ESIMS. The absolute configurations were identified on basis of the quantum chemical calculations of ECD and NMR, as well as the modified Mosher’s method. It's particularly noteworthy that the tetrasubstituted furopyrans, chenopodolans A-F, possessing phytotoxicity and zootoxicity, were structural misassignments. The structures of chenopodolans featuring with furopyran skeleton were revised as common trisubstituted α-pyrones by computational chemistry, NMR spectroscopic method, and empirical rule. Compounds 1, 2, 7, and 9 showed significant anti-inflammatory activity with IC50 values ranging from 3.6 to 22.8 μM, which is better than the positive control indomethacin (IC50 = 26.5 ± 1.13 μM). This discovery holds potential for the development of new anti-inflammatory agents.