An unusual 1(10→19)abeo steroid from a jellyfish-derived fungus

[Display omitted] •A new C25 abeo-sterol (phomarol) was isolated from a jellyfish-derived fungus.•Phomarol is unique with a 7-membered carbocyclic A ring [1(10→19)abeo].•The structure was established by NMR, modified Mosher’s method, and ECD. A structurally unique C25 steroid (phomarol) was isolated from a cultured fungus (Phoma sp.) derived from the giant jellyfish Nemopilema nomurai. Its planar structure and relative configuration were established by analyzing 1D and 2D NMR data, and its absolute configuration was determined using the modified Mosher’s method and ECD calculation. Phomarol is unique with a 7-membered carbocyclic A ring [1(10→19)abeo], an aromatic B ring, and a side chain cyclized to form a fused pentacyclic skeleton.