Metabolic products of microorganisms, 271. Momofulvenone A and B, new benzo[b]fluorene quinones from Streptomyces

From the cultures of Streptomyces diastatochromogenes (strain Tü 2895) two novel benzo[b]fluorene quinones, named momofulvenone A (1) and B (2), were isolated. Difficulties in their spectroscopic characterization due to salt effects were overcome by fermentation in the presence of ammonium acetate. The structures were established by a detailed spectroscopic analysis. The polyketide origin of 1 and 2 was verified by feeding [1,2‐13C2]acetate to the growing cultures of Tü 2895. The momofulvenones represent the nitrogen‐free parent compound of the kinamycin family of antibiotics.