Secondary metabolites isolating from fermentation broths

As examples of other naphthalenoid ansamycin antibiotics, rubradirin (70) and protorubradirin (71) were isolated from the fermentation broth of Streptomyces achromogenes var. rubradiris [109-114,117]. As indicated previously, protorubradirin (71) is the C-nitroso-analogue of 70, and it seems that 71 is the true secondary metabolite produced by S. achromogenes var. rubradiris. Thus, rubradirin (70), reported earlier, is the photo-oxidation product of protorubradirin (71). The ansa moiety of these compounds possesses a C9 chain, instead of a C or a C23 chain. 

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