Two new antibiotics, CJ-16,264 (I) and "CJ-16,367 (II), were isolated from the fermentation broth of an unidentified fungus CL39457. These antibiotics have a pyrrolizidinone skeleton, first discovered in fungi. Compounds I and II inhibit the growth of Gram-positive multi-drug resistant bacteria and some Gram-negative strains such as Moraxella catarrhalis and Escherichia coll with altered permeability (imp). Comparison of an antibacterial profile between the two compoundssuggested that the gamma-lactone portion of I is important for the activity.

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