Chalcomycin B, a new macrolide antibiotic from the marine isolate Streptomyces sp. B7064.

In our screening of marine streptomycete isolates for bioactive components, a new macrolide antibiotic designated as chalcomycin B (1b) was isolated from the culture broth of a marine Streptomycete isolate B7064 together with chalcomycin (1a) as the active principles. The structure of the new antibiotic was determined by EI and ESI MS, 1H, 13C and 2D NMR spectroscopy and by comparison of the NMR data with those of chalcomycin.