SYNTHESIS AND LABELING CHARACTERISTICS OF TC-99M-MERCAPTOACETYLTRIPEPTIDES

A number of derivatives of mercaptoacetyltriglycine in which one or mo re of the three glycyl moieties are replaced by other amino acids such as D- or L-alanine, D-serine, D-2-aminobutyric acid, D-valine or D-ph enylglycine have been synthesized and labelled with technetium-99m. La belling with technetium yielded in each case a mixture of mainly two r adioactive species, which probably are diastereomeric oxotechnetium (V ) complexes originating from the presence of a chiral carbon atom in t he ligands. The diastereomers were separated by reversed phase HPLC, E xcept for the serine derivative, all radiolabelled derivatives have a longer retention time than the parent compound Tc-99m-MAG3. The relati ve amount of the two diastereomers formed upon labelling is dependent on the nature of the ligand but can be influenced to a limited extent by the pH of the exchange labelling mixture.