Photoredox Modification of Aliphatic Amino Acids

The modification of biological macromolecules (e.g. proteins, nucleic acids, carbohydrates) with various tags, probes or functional groups has been a longstanding desire for both chemists and biologists to aid in the elucidation of their biological structure and/or function. In particular, modification of proteins has been used to uncover many cellular processes and identify numerous aberrant proteins responsible for disease. A large toolbox of reagents and methodologies are now available that enable modification of many of the canonical or unnatural amino acids. Protein modification can occur on the side chain of the target amino acid or on the N or C termini of the protein. Although significant progress has been made in the development of chemical tools that facilitate modification of many of the 20 native amino acids, there are currently no methodologies available that enable convenient modification of amino acids containing no obvious reactive functionality in their side chains. Modification of the aliphatic amino acids (leucine, isoleucine and valine) has proven particularly elusive. It would be beneficial to the scientific community as a whole to have tools that allow modification of all proteinogenic amino acids. The aim of this work is to use photoredox methods to enable the modification of aliphatic amino acids.