Visible-light-mediated C–S bond activation in cysteine derivatives with quinoxalinones for the synthesis of heteroaryl amino acids†

Synthetic strategies for selective chemical modification of natural amino acids and peptides are constantly greatly needed in current state-of-the-art therapeutics. Herein, we report photocatalytic C–S bond activation in cysteine derivatives with quinoxalinones for the synthesis of pharmacologically interesting heteroaryl amino acids. A series of quinoxalinone-conjugated amino acids and oligopeptides as well as caffeine- and isoquinoline-containing amino acids were efficiently obtained through desulfurative heteroarylation of cysteine derivatives. The given approach features a wide substrate scope, mild conditions, good yields and operational simplicity. Furthermore, the N-propargyl quinoxalinone-conjugated amino acids produced can be successfully integrated with biotin–PEG3–azide through click chemistry for potential applications in immunology and histochemistry.