The solid phase synthesis and NMR spectroscopy of a 99Tc chelate–bombesin derived peptide conjugate

A bombesin derived peptide–99Tc chelate conjugate was prepared using a solid phase synthetic methodology. The reported approach involved linking a prefabricated bifunctional N2N′S technetium chelate complex to a resin bound peptide sequence derived from bombesin, which has been shown to bind to the gastrin-releasing peptide (GRP) receptor. The technetium chelate–peptide conjugate was subsequently isolated from the solid support and characterized by electrospray mass spectrometry, HPLC and NMR spectroscopy. The goal of the approach was to develop a versatile solid phase synthetic procedure that would facilitate the future application of modern drug discovery techniques for the development of receptor selective technetium radiopharmaceuticals. Furthermore, the NMR studies of the reported radiometal–peptide conjugate provide an important reference for the characterization of future bombesin-based radiopharmaceuticals.