New antibiotics SF2315A and B produced by an Excellospora sp. I. Taxonomy of the strain, isolation and characterization of antibiotics.

Two new antibiotics SF2315A and B have been isolated from culture filtrate of an actinomycete strain, Excellospora viridilutea SF2315. They are weakly active against Gram-positive bacteria and inhibited reverse transcriptase of avian myeloblastosis virus. Empirical molecular formula of antibiotics SF2315A and B were determined to be C19H16O5 and C19H20O6, respectively.