ABSTRACT
An essential requirement in chemical peptide synthesis is the appropriate selection and use of a temporary protecting group for the a-amino group of amino acids. As described in Chapter 2 of this volume, the experimental design of the synthesis and subsequently chosen orthogonal protection scheme largely dictate the choice of N"-protection. Such protection is mandatory in solid phase synthesis (SPS) as it permits a-carboxy activation and subsequent selective condensation of the N"-protected amino acid onto the free amine of the terminal amino acid of the growing peptide chain. The temporary protecting group must meet several strict requirements in order to allow successful SPS. The group must not affect the optical integrity of the amino acid derivative. It must withstand completely the conditions of SPS, cause no side reactions, and be rapidly, efficiently, and selectively cleaved under conditions that leave unaffected any amino acid side-chain ("permanent") protecting groups.
