Biomimetic Synthesis of Cyanogramides B and C

Marinacarboline E and cyanogramides B and C from the marine-derived bacterium Actinoalloteichus cyanogriseus have been synthesized. The key step is the Baeyer–Villiger oxidation of marinacarboline E to a ketene aminal via O → N acetyl migration, followed by addition of water or MeOH. Replacing the phenylethyl by a styryl side chain afforded dehydromarinacarboline E that was oxidized to a tetracyclic aminal. This study contributes to the chemical understanding of the enzymatic conversions in the biosynthesis of the cyanogramides.