SYNTHESIS OF A SELECTIVE SIGMA-RECEPTOR RADIOLIGAND FOR SPECT - [I-123] (2-HYDROXYETHYL)-4-(4-IODOPHENOXYMETHYL)PIPERIDINE

[I-123]-1-(2-Hydroxyethyl)-4-(4-iodophenoxymethyl) has been prepared a s a novel sigma receptor radioligand for tumour imaging by SPECT. This ligand was found to be selective in vitro for the sigma-1 receptor (K i = 2.3 nM) when tested in a variety of neuroreceptor binding assays. The lipophilicity of this ligand is appropriate for crossing the blood /brain barrier (log P-7.5 = 4.0) Radioiodination was accomplished by n o-carrier-added iododestannylation using chloramine-T in acetic acid. The specific activity of the radiotracer >10,000 mCi/mu mole. The radi ochemical yield was 63-77% EOS and the radiochemical purity was >99%.