Synthesis of rhenium complexes as models for new sigma receptor imaging agents
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The sigma receptor has been biologically found to play roles in the central nervous system (CNS) disorders and cancer cell proliferation. With the identification of lead sigma receptor binding ligands by previous structure activity relationship (SAR) studies, new sigma Tc-⁹⁹[superscript m] sigma receptor imaging agents were designed. Tc-⁹⁹ [superscript m] imaging agents provide the advantages for routing clinical use due to its ideal nuclear properties (t₁/₂=6 hours and 140 keV gamma photon emission) and being readily available from a ⁹⁹Mo/⁹⁹[superscript m] Tc generator. The stability, structure, and biodistribution of rhenium complexes have been found similar to their Tc-⁹⁹ [superscript m] counterparts. Non-radioactive rhenium surrogates serve as a useful precursor for the radioactive Tc-⁹⁹ [superscript m] imaging agents. The Re/Tc-⁹⁹ [superscript m] are bound by the amide-amine-dithiol tetradentate (AADT) chelate and linked onto the sigma moieties following the bifunctional chelate approach. The current study, successfully synthesized the chelate, sigma moieties, and target rhenium surrogates toward the goal of developing new sigma receptor imaging agents.