Preparation of the functionalizable methionine surrogate azidohomoalanine via copper-catalyzed diazo transfer

The azide functional group has assumed a prominent role in chemical biology efforts in recent years. Azides may be readily introduced into proteins upon replacement of methionine residues with the non-canonical amino acid azidohomoalanine (AHA). This protocol describes a synthetic route to AHA based on the copper-catalyzed conversion of amines to azides. An alternate protocol for the preparation of AHA is presented in a companion paper. The synthesis and purification of AHA via the route described herein can be completed in 3–4 days.