Rapid and Selective Chemical Editing of Ribosomally Synthesized and Post‐Translationally Modified Peptides (RiPPs) via Cu(II)‐Catalyzed β‐Borylation of Dehydroamino Acids

We report the fast and selective chemical editing of ribosomally synthesized and post‐translationally modified peptides (RiPPs) by β‐borylation of dehydroalanine (Dha) residues. The thiopeptide thiostrepton was modified efficiently using Cu(II)‐catalysis under mild conditions and 1D/2D NMR of the purified product showed site‐selective borylation of the terminal Dha residues. Using similar conditions, the thiopeptide nosiheptide, lanthipeptide nisin Z, and protein SUMO_G98Dha were also modified efficiently. Borylated thiostrepton showed an up to 84‐fold increase in water solubility, and minimum inhibitory concentration (MIC) assays showed that antimicrobial activity was maintained in thiostrepton and nosiheptide. The introduced boronic‐acid functionalities were shown to be valuable handles for chemical mutagenesis and in a reversible click reaction with triols for the pH‐controlled labeling of RiPPs.