Utilizing Copper-Mediated Deprotection of Selenazolidine for Cyclic Peptides Synthesis

Selenazoliline (Sez) was originally developed as a masking form of selenocysteine (Sec) for the chemical synthesis of challenging proteins. Here we utilize Sez and our recent reported copper(II)-mediated deprotection for the synthesis of cyclic peptides. This approach allows deprotection, cyclization and deselenization in one-pot, providing several different cyclic peptides in good yields. In addition, the Sec can also be retained, which enhance the oxidative folding of disulfide-rich cyclic proteins, such as the case of Kalata S.