Visible Light-Driven Benzylic C(sp³)–H Carboxylation Enables Synthesis of ¹³C-Labeled (±)-α-Amino Acids with ¹³C-Formate

13C-labeled α-amino acids are important molecules in biological studies and drug development. Cost-effective synthesis of α-amino acids with a high level of 13C incorporation under mild conditions remains limited. Herein, we report the development of a benzylic C(sp3)–H carboxylation method to prepare highly 13C-labeled α-amino acids, i.e., arylglycines, using near-stoichiometric and user-friendly sodium 13C-formate. The sequential reaction pathway of in situ 13C-carbon dioxide (CO2) generation followed by C–H carboxylation via 1,2-HAT was suggested by mechanistic studies.