The Structure of Carbazomycin B

Abstract

The structure of carbazomycin B was determmed to be i-hydroxy-3-methoxy-1,2-dimethylcarbazole by 'H-and 13c-nmr studies of carbazomycin B and its derivatives, and was unequivocally confirmed by X-ray crystallographic analysis.Carbazomycins A and B were isolated mainly from the cultured mycelia of an unidentified Streptomyces which was also proved to produce viomycin simultaneously.Carbazomycm B was the main antibiotic active against some klnds of phytopathogenic fungi and further showed weak antibacterial and antiyeast activities, while carbazomycin A was the minor component and showed extremely weak biological activities against the above microbes.The more polar pale yellow substance, carbazomycin B (I), mp 137.5-138.0°,had a molecular formula C15H15N02 and its ir spectrum showed an aromatic system with an -NH-function and a hydroxyl group.The uv spectrum of I was very similar to those of carbazole derivatives suggesting the presence of a carbazole skeleton.The l ~-n m r spectrum of I revealed the presence of an -NH-function, one phenolic hydroxyl, one aromatic methoxyl and two aromatic C-methyl groups besides four aromatic protons.Prom these data carbazomycin B (I) was suggested to be a carbazole derivative with one hydroxyl, one methoxyl and two methyl groups on the nucleus.'Zinc dust distillation of I afforded carbazole conflrminq the