Synthesis, radiolabeling and baboon SPECT imaging of 2β-carbomethoxy-3β-(3′-[123I]iodophenyl)tropane ([123I]YP256) as a serotonin transporter radiotracer

To develop a potential SPECT probe to evaluate the integrity of the serotoninergic system (5-HTT) whose dysfunction is linked to several disease conditions such as Parkinson's disease, Alzheimer's disease and depression, we report the synthesis, radiolabeling and in vivo baboon imaging of 2β-carbomethoxy-3β-(3′-[123I]iodophenyl) tropane (YP256, 6). The radiolabeling was performed by iododestannylation using sodium [123I]iodide and peracetic acid. Although the ligand displayed high selectivity for 5-HTT over dopamine transporter in vitro, SPECT imaging in baboons did not reveal selective 5-HTT accumulation in brain in vivo.