Photoinduced\nRadical Approach for Desulfurative Alkylation\nof Cysteine Derivatives to Make Unnatural Amino Acids

Unnatural amino acids (UAAs) are\nhighly valuable molecules\nin organic\nsynthesis, pharmaceutical sciences, and material science. Herein,\nwe present a photocatalytic radical approach for desulfurative alkylation\nof cysteine derivatives with arenethiol as the hydrogen atom transfer\ncatalyst for making UAAs and peptides. The formate salt, acting as\nthe hydrogen atom donor, in situ generates the highly reductive CO<sub>2</sub> radical anion species, which is the key to unlocking the\nC–S bond cleavage process with a simple benzoyl protecting\ngroup. No photocatalyst is required for the radical initiation and\npropagation, which makes such a visible-light-induced process mild,\nefficient, and sustainable.