Radiolabelling characteristics of novel iminophosphorane ligands with technetium-99m

Abstract

A variety of unconventional phosphorus-nitrogen (P-N) backbone ligands have been synthesized with a unique, chemically flexible heterobifunctional ligand system that has the capability to complex with a radioactive metal ion and to link a bioactive peptide. We approach the synthesis of the iminophosphorane ligands (P-N) through the reaction of silylaminophosphines, T 2 NPR 2 (T=SiMe 3 ). The P-N compounds which are derived from the applications of these silylaminophosphine reactions with a diversity of organic substrates, have the capability to attach 99m Tc by means of a covalent bond. A further advantage of these type of chelating agents is their ability to selectively react with 99m Tc in a +7 oxidation state and in the absence of reducing agent. This type of ligand presents the possibility of forming a metal-nitrogen σ bond with a high oxidation-state early transition metal via the elimination of Me 3 SiCl. The properties of the resulting chelates with these ligands can be readily modified by introducing a variety of substituents on the P or N atoms (R or R'). Several studied P-N ligands have been shown to hold the potential for preparing stable 99m Tc-complexes with high labelling yield under the mild labelling conditions and with and without reducing agents. Furthermore, the labelled P-N compounds showed a high stability both when incubated with plasma and when challenged with excess amount of cysteine.