Peptides coupling, copper chloride

Racemization Suppression in Peptide Couplings. A mixture of copper(It) chloride and triethylamine catalyzes the formation of peptide bonds. Furthermore, when used as an additive, CuCl2 suppresses racemization in both the carbodiimide and mixed anhydride peptide coupling methods. Recently it was shown that a combination of 1-hydroxybenzotriazole and CuCl2 gives improved yields of peptides while eliminating racemization. ... 

It has been known for some time that ligands 27, 35, and 36 can be used for direct synthesis of oxidized Cu(I) chloride solutions which are useful catalysts for oxidative coupling processes (26,27). Amide and lactam ligands contain the nitrogen atoms of amines (which generally promote Cu(I) oxidation, see above) and also serve as crude models for the peptide link of proteins, which is the general environment of copper found in oxidases (28). 

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