New antibiotics SF2315A and B produced by an Excellospora sp. II. The structural elucidation

The structures of antibiotics SF2315A and B were determined to be [4aR-(4a beta,12b beta)] or [4aS-(4a alpha,12b alpha)]-4a,5,6,12b-tetrahydro-4a,8-dihydroxy-3- methylbenz[a]anthracen-1,7,12(4H)-trione and [1S-(1 beta,4a beta,6a beta,12 beta,12a beta,12b beta)] or [1 R-(1 alpha,4a alpha,6a alpha,12 alpha,12a alpha,12b alpha)]- 1,4,4a,5,6,6a,12a,12b-octahydro-1,4a,8,12-tetrahydroxy-3-methyl-6a ,12a- epoxybenz[a]anthracen-7(12H)-one, respectively from their spectroscopic analyses and single crystal X-ray diffraction analyses.