Homogeneous large target molecules are probably best produced chemically by convergent strategies that rely on the union of peptide segments. Most modern convergent peptide synthesis strategies are based to some extent on the use of solid-phase methods because of the advantages in economics and rapidity that these present. If the protected peptide segments themselves are also synthesized using solid-phase methods, then the advantages of the rapidity of SPPS and those of the purification and characterization of the intermediates of classical synthesis in solution are combined. This strategy has been termed convergent solid-phase peptide synthesis (CSPPS). The first stage in a CSPPS strategy is the solid-phase synthesis of the various protected peptide segments corresponding to the amino acid sequence of the target molecule. Protected, as opposed to free, peptide segments are required because, generally speaking, in order to couple them in an unambiguous manner, they must be protected at all reactive functional groups except those required for amide bond formation.