Sorbicillasins A⁻B and Scirpyrone K from a Deep-Sea-Derived Fungus, Phialocephala sp. FL30r.

Two new nitrogen-containing sorbicillinoids named sorbicillasins A and B (1 and 2) and a new 3,4,6-trisubstituted α-pyrone derivative, scirpyrone K (3), together with two known biosynthetically related polyketides (4⁻5), were isolated from the deep-sea-derived fungus Phialocephala sp. FL30r by using the OSMAC (one strain-many compounds) method. The structures of 1⁻3, including absolute configurations, were deduced based on MS, NMR, and time-dependent density functional theory (TD-DFT) calculations of specific ECD (electronic circular dichroism) spectra. Compounds 1 and 2 possessed a novel hexahydropyrimido[2,1-a] isoindole moiety, and compound 3 exhibited weak radical scavenging activity against DPPH (2,2-diphenyl-1-picrylhydrazyl) with an IC50 value of 27.9 μM.