Fermentation, isolation, characterization and structure of antibiotic U-58,431.

A new antibiotic U-58,431 has been isolated from the fermentation broth of Streptomyces helicus DIETZ and LI, sp. n. (UC-5837) and the structure of this antibiotic, namely, 6-amino-3,4,5,8-tetrahydro-4,9-dihydroxy-3-methyl-5,8-dioxo-1,4-ethano-1H-2-benzopyron-7-carboxamide has been determined by X-ray crystallography. The antibiotic inhibits a variety of Gram-positive and Gram-negative bacteria in vitro. However, it is toxic to mice and does not protect experimentally infected animals when administered at the maximum tolerated dose.