Eremophilane-Type Sesquiterpenes from the Fungus Xylaria sp. BCC 21097

Seven new eremophilane-type sesquiterpenoids (15, 7, and 8) and the known mairetolide F (6) were isolated from the endophytic Xylaria sp. BCC 21097. A new furofurandione (9) was also isolated from the fungal extract. The structures of the new compounds were elucidated by analyses of NMR spectroscopic and mass spectrometry data in combination with chemical reaction studies. Eremophilanolides possessing an α-methylene-γ-lactone (13) exhibited moderate cytotoxic activities, while related analogues bearing an endo double bond (6 and 7) were inactive.