Julichrome Monomers from Marine Gastropod Mollusk‐Associated Streptomyces and Stereochemical Revision of Julichromes Q3·5 and Q3·3

Two julichrome monomers, julichromes Q11 (1) and Q12 (2), along with five known julichromes (Q10 , Q3 5 , Q3 3 , Q6 6 , Q6 , 3-7) and four known anthraquinones (chrysophanol, 4-acetylchrysophanol, islandicin, huanglongmycin A, 8-11), were isolated from the marine gastropod mollusk Batillaria zonalis-associated Streptomyces sampsonii SCSIO 054. This is the first report of julichromes isolated from a marine source. Extensive dissection of 1D and 2D NMR datasets combined with X-ray crystallography enabled rigorous elucidation of the previously reported configurations of julichrome Q3 5 (4) and related julichrome Q3 3 (5); both of the configuration at C(9) needs to be revised. In addition, julichrome Q12 (2) was found to display antibacterial activity against Micrococcus luteus and Bacillus subtilis with MICs of 2.0 and 8.0 mug mL(-1) ; four compounds (1, 3, 6, 7) also showed inhibitory activities against an array of methicillin-resistant Staphylococcus aureus, S. aureus and S. simulans AKA1 with MIC values ranging from 8 to 64 mug mL(-1) .