Electrochemically clicking on tyrosine

Bioorganic Chemistry Proteins are readily modified at lysine or cysteine residues, but for the other amino acids, general methods still need to be developed. For example, for electron-rich tyrosine, click methods have been developed based on cyclic diazodicarboxyamide anchors, but activation with chemical oxidants can also modify lysine residues or create products with limited aqueous stability. Alvarez-Dorta et al. show that tyrosine residues on proteins, including insulin and bovine serum albumin, can be targeted by electrochemically oxidizing phenyl urazoles without affecting amine or thiol groups of other amino acids. A reactive N=N species generated in the five-membered ring reacts with the C–H bonds adjacent to the tyrosine OH group. J. Am. Chem. Soc. 140 , 17120 (2018).