Three naphthomycin type polyketide compounds isolated from strain Streptomyces sp. HKIB0008

Three new naphthomycin derivatives were isolated and identified from Streptomyces sp . HKIB0008, and were designated as naphthomycin R ( 1 ), naphthomycin S ( 2 ), and naphthomycin T ( 3 ). Their structures were elucidated using a combination of spectroscopic techniques, including high-resolution mass spectrometry, and NMR. The naphthoquinone core of 1 underwent carbon–carbon bond cleavage, resulting in a novel structural feature, and a corresponding Baeyer–Villiger oxidation mechanism was proposed. Compounds 2 and 3 possess a complex side chain when compared to known cystine modification on the naphthalenoid core as in the case of naphthomycins I and J. In addition, the minimum inhibitory concentration (MIC) assays for these compounds were conducted.