By chemical screening methods we detected in the mycelium of Streptomyces griseoflavus (strain Tii 2880) the colabomycin-complex and a second compound called 2880-ll. 2880-ll was separated from crude extracts by silica gel chromatography and further purified by repeated chromatography on Sephadex LH-20 yielding a yellow amorphous powder. Its physico-chemical properties (MP 272°C; IR, UV, electron impact mass spectra, ¹H NMR, ¹³C NMR) were characterized. Structural elucidation via nuclear Overhauser enhancement difference experiments and spectral analyses revealed 2880-ll as (E)-N-(3-hydroxy-1-oxocyclopent-2-en-2-yl)-3-(4-hydroxy-3-methoxyphenyl)propenamide. Biosynthetically, it could be derived from ferulic acid and 2-amino-3-hydroxycyclopent-2-enone. In disc-diffusion assays against Gram-positive and Gram-negative bacteria, yeasts and fungi, 2880-ll showed no significant inhibitory activity up to 1 mg/ml.