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Chemoselective and site-selective peptide and native protein modification enabled by aldehyde auto-oxidation.

We report a chemoselective and site-selective formylation of ε-amine in native proteins. The aldehyde auto-oxidation re-routing, regulated generation of formate, and reversible N-terminus protection drive the transformation. It labels a single ε-amine in a pool of its copies, other nucleophilic residues, and α-amine. The extension of the methodology leads to site-selective acylation.