Structures and biosynthesis of aflastatins: novel inhibitors of aflatoxin production by Aspergillus parasiticus.

Two novel inhibitors of aflatoxin production by Aspergillus parasiticus were isolated from the mycelial extracts of Streptomyces sp. MRI142 and termed aflastatin A and B. The structures of aflastatin A (1) and B (5) were elucidated by NMR and chemical degradation experiments. These compounds have a novel skeleton of a tetramic acid derivative with a highly oxygenated long alkyl chain. The incorporation experiments using 13C-labeled acetates, propionate, glucose and glycolate suggested that most of the C2 and C3 units involved in the alkyl chain moiety of aflastatin A were biosynthesized from acetic and propionic acids, but five C2 units in the alkyl chain originated from glycolic acid.