Copper(II)-mediated C-H sulphenylation or selenylation of tryptophan enabling macrocyclization of peptides.

Cu(II)-mediated C-H sulphenylation or selenylation of Trp indole by a derivative of cysteine or selenocysteine enables access to the tryptathionine unit or its selenium congener. The mechanism of these protocols, which allow macrocyclization of Trp-containing peptides, has been studied.