Tandem Electrochemical Oxidative Azidation/Heterocyclization of Tryptophan-Containing Peptides under Buffer Conditions.

As the aromatic tryptophan (Trp) side chain plays a pivotal role in influencing the structure and function of peptides and proteins, it has become an attractive target for the late-stage modification of these important biomolecules. Herein, we report an electrochemical approach for late-stage functionalization of peptides containing a Trp side chain through manganese-catalyzed tandem radical azidation/heterocyclization. This electrochemical oxidative strategy provides access to azide-substituted tetrazolo[1,5-a]indole-containing peptides with broad functional group tolerance, high site selectivity, and good yields of products (up to 87 %) under mild buffer conditions. Moreover, the modified Trp-containing peptides bearing an azide functionality are promising building blocks, paving the way for the construction of various derivatives, such as "click" chemistry products.