Investigations of Novel NxSy Technetium and Rhenium Chelants

Abstract

This thesis describes the synthesis and complexation of amino acid based chelants for technetium and rhenium. All of the chelates were of the NxSy type. An initial N2S2 diamido dithiol peptide of the type mercaptoacetic acid-serine-cysteine was synthesized and coordinated with both rhenium and technetium. The complexes were analysed by NMR spectroscopy and found to retain the benzyl moieties. Syn and anti diastereoemers were produced with one conformation preferred over the other. This was not true of another chelant RP294 supplied by Resolution Pharmaceuticals. The N2N1'S1 chelant consisted of dimethyl-glycine-serine-cysteineglycine and was a novel variation of the N2S2 tripeptide used initially. The coordination of this N3S chelant to technetium resulted in the formation of equal 1:1 quantities of diastereomers. Analysis was done by NMR spectroscopy and electrospray mass spectrometry. The two diastereomers were found to slowly interconvert and a mechanism for the interconversion proposed. The radiopharmaceutical RP128 (dimethylglycineserine-cysteine-glycine-threonine-lysine-proline-proline-arginine), of which the RP294 is the chelating portion, was coordinated to technetium. Analysis of the bifunctional chelant and its coordination complex by NMR spectroscopy demonstrated that the targeting portion of the molecule was unaffected by the technetium. Two diastereomers of the TcO(RP128) complex were found, as seen for the chelating portion of the molecule, TcO(RP294).