Metabolic products of microorganisms. 243. Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger.

Pyridazomycin, a new antifungal antibiotic produced by Streptomyces violaceoniger sp. griseofuscus (strain Tü 2557), was detected in a selective screening against Mucor hiemalis (Tü 179/180). The amino acid side chain of 1 can be seen as L-ornithine, whose gamma-nitrogen atom is part of a pyridazine ring building a quaternary ammonium system. The structure of 1 was established by spectroscopic analysis of the parent compound and degradation products. The occurrence of a pyridazine ring in microbial secondary metabolites is unique.