Development of Ts-Protected Selenocysteine for Sec-Conjugate Arylation via a Reductive Coupling Approach

Selenocysteine (Sec)-containing peptides possess distinctive chemical properties, offering broad potential in biological regulation and therapeutic development. Herein, we report the design of highly electrophilic Ts-protected Sec precursors and the development of a nickel/phenanthroline-catalyzed reductive coupling strategy that enables the efficient arylation of Sec residues using aryl halides under mild conditions. This method exhibits a broad substrate scope and excellent functional group tolerance, accommodating thiol, guanidino, carboxylic acid, and amino groups. Moreover, it can be applied to the synthesis of cyclic peptides and late-stage functionalization of a bioactive peptide.