Coupling reagents in peptide synthesis

All coupling methods have the same reaction principle in common:after activation of the carboxy group of the first amino acid, thesecond amino acid can form the peptide bond by a nucleophilicattack of its amino group. In order to prevent uncontrolledpeptide bond formation the amino group of the first amino acidand all functional side chain groups need to be reversibly blocked.Repeated de-blocking, activation, and coupling build the peptideto its desired final sequence.