Arthpyrones A-C, Pyridone Alkaloids from a Sponge-Derived Fungus Arthrinium arundinis ZSDS1-F3

Three new 4-hydroxy-2-pyridone alkaloids, arthpyrones A-C (1-3), were isolated from the sponge-derived fungus Arthrinium arundinis ZSDS1-F3. Their structures were elucidated on the basis of spectroscopic analysis, CD spectra, quantum chemical calculation, and X-ray single-crystal diffraction analysis. Compounds 1 and 2 possessed a 2-pyridone core featured with a decalin moiety linked via a carboxide bridge bearing a novel oxabicyclo[3.3.1]nonane ring system rarely discovered in nature. A possible biosynthetic pathway for them was proposed.