Altenuene derivatives from an unidentified freshwater fungus in the family Tubeufiaceae

Four new altenuene derivatives called dihydroaltenuenes A (1) and B (2) and dehydroaltenuenes A (3) and B (4), along with five known compounds, including isoaltenuene (5), altenuene (6), and 5'-epialtenuene (7), were isolated from cultures of an unidentified freshwater aquatic fungal species in the family Tubeufiaceae. The structures of 1-4 were determined by analysis of NMR and MS data. The relative stereochemistry was determined on the basis of H-1 NMR J-values and NOE data, while the absolute configuration of a representative member of the group (5) was assigned by CD spectral analysis of its bis-N, N-dimethylaminobenzoate derivative. Compounds 1, 3, 4, 5, and 6 showed antibiotic activity against Gram-positive bacteria.