Synthesis of bombesin analogs by the Fmoc method

Bombesin synthesis has previously been achieved by the Merrifield method. Severe conditions and repetitive acidic treatments have led to the selection of a milder method for improving effectiveness. This study describes a new technique for the synthesis of bombesin and its analogs based on the use of fluorenylmethoxycarbonyl (Fmoc) protected amino acids and continuous flow solid phase procedure. Peptide elongation is realized by the intermediaries of derived pentafluorophenyl ester amino acids. Peptides of different lengths were synthesized in order to determine the minimal length of peptide chain needed to obtain immunoreactivity comparable to that of natural bombesin. Purification and analysis of the products by FPLC and amino acid determination were performed. Immunoreactivity study of these peptides was measured by a competition radioimmunoassay with an antiserum directed against the C-terminal portion. Results suggest that a decapeptide analog is sufficient for bombesin to be recognized by the antibody or as a carrier in targeting therapy.