Abstract: A method for synthesizing a given peptide or its derivative which contains a proline residue or a proline derivative, at proximity to, or at, the C-terminal end of said peptide is provided. The method comprises a) synthesizing on a first resin a C-terminal portion of said peptide, or its derivative, comprising at least three successive amino acid residues or their derivatives, by successive coupling of selected amino acids, small peptides or their derivatives; b) cleaving the C-terminal portion from said first resin; c) reattaching said C-terminal portion to a second resin which is generally suitable for the synthesis of peptides but is unsuitable for the formation of peptides having a proline residue positioned at the C-terminal end of said peptide; and d) coupling selected amino acids, small peptides or derivatives to the C-terminal portion.