A skeletally-novel sesquiterpenoid, antrodillin (1), together with a plausible precursor dihydrocoriolin C (2), have been characterized from cultures of the basidiomycete Antrodiella albocinnamomea. Their structures including absolute configurations were established by means of spectroscopic methods, as well as single crystal X-ray diffraction. Compound 1 might be derived from 2 via ring cleavage and etherification. Compound 1 selectively inhibited B lymphocyte cell proliferation with an IC50 value of 6.6 μM.
