Protecting Groups in Peptide Synthesis.

The protection of amino acid reactive functionalities including the α-amino group, the side chain (amines, carboxylic acids, alcohols, and thiols), or the carboxylic acid terminus is an essential strategy in peptide chemistry. This is mandatory to prevent polymerization of the amino acids and to minimize undesirable side reactions during the synthetic process. Proper protecting group manipulation strategies can maximize the yield of the desired product or allow the construction of complex peptide-based structures. Thus, the compatibility and orthogonality of each protecting group are key to achieve the proper control of molecular structure. Herein, we describe some common protecting groups and their general unmasking methods, in order to mask and expose amine, carboxylic acid, alcohol, and thiol functionalities to achieve the synthesis of peptides and related molecules.