New cyanocyclines from a cyanide-treated broth of Streptomyces lusitanus

Organic extracts of Streptomyces lusitanus, the producer of the anticancer antibiotic naphthyridinomycin [1], were found to contain two additional compounds active in an antibiotic screen. As with 1, these reacted with NaCN added at the end of the fermentation. One of the addition products has been named cyanocycline B [3] and is derived from N-desmethylnaphthyridinomycin [4], while the other has been named cyanocycline C [5], and is derived from the hydroquinone 6 of 1. Cyanocycline C is unstable and was characterized after conversion to the dimethyl derivative with CH2N2 in the presence of TFA. The implications of these metabolites for the biosynthesis of 1 are discussed. A third new antibiotic, cyanocycline D [8] was isolated from the cyanide-treated broth and proved to be an artifact in which the oxazolidine ring had been opened by cyanide. The potential relevance of the formation of 8 to the reaction of 1 with DNA is also discussed.