First practical protection of alpha-amino acids as N,N-benzyloxycarbamoyl derivatives

The consecutive treatment of N-Cbz amino protected compounds with LiHMDS and CbzCl provides a practical method for the preparation of N,N-benzyloxycarbamoyl (N,N-di-Cbz) derivatives in good yield. When alpha-amino acids are used the protection occurs without racemization. The method is compatible with a wide range of other functional and protecting groups. The procedure is also valid for the synthesis of mixed N,N-carbamoyl derivatives.