Anthranosides A-C, Anthranilate Derivatives from a Sponge-Derived Streptomyces sp. CMN-62

Three new derivatives, anthranosides A-C (1-3), were discovered from a marine sponge-derived actinomycete Streptomyces sp. CMN-62. Their structures including absolute configurations were elucidated using MS and NMR spectroscopic data, X-ray single-crystal diffraction analysis, and chemical synthesis. Compounds 1 and 2 are epimers composed by linking the anthranilate unit to the fructofuranose moiety via a carbon-nitrogen bond, while 3 possessed a unique indole-containing scaffold. All compounds were tested for cytotoxicity, anti-influenza H₁N₁ virus, and NFκB inhibitory activities, and 3 showed anti-influenza activity. A possible Amadori rearrangement-based biosynthetic pathway was proposed to generate compounds 1-3.