Noreupenifeldin, a tropolone from an unidentified ascomycete

Noreupenifeldin (2), a new monotropolone derivative of the bistropolone eupenifeldin (1), was isolated from an unidentified ascomycete by bioassay-guided fractionation as part of our search for new anthelmintics. The structure of 1 was confirmed by comparison with literature data. The structure of 2 was elucidated from MS and 1D and 2D NMR data. Compounds 1 and 2 are diastereomers of pyenidione (3) and epolone A (4), respectively. Compounds 1-3 were evaluated for their anthelmintic activity against the parasitic worm Hemonchus contortus. Compounds 1 and 3 exhibited modest in vitro activity, showing EC(90) 50 and 83 mu g/mL, respectively, in reducing motility of L3 larvae of H. contortus. Compound 2 was inactive, indicating that the second tropolone moiety is required for activity.