Synthesis and preliminary in vivo evaluation of 4-[I-123]iodo-N-{2-[4-(6-trifluoromethyl-2-pyridinyl)-1-piperazinyl]ethyl} benzamide, a potential SPECT radioligand for the 5-HT1A receptor

4-[I-123]Iodo-N-{2- [4-(6-trifluoromethyl-2-pyridinyl)-1-piperazinyl]ethyl} benzamide ((1) under bar.I-123), a potential SPECT 5-HT1A radioligand, was synthesized by electrophilic iododestannylation of the tributyltin derivati ve with n.c.a. [I-123]NaI and chloramine-T under acidic conditions (20 min, ambient temperature). Radiochemical yield averaged around 60 % (s(d)=8, n= 22). After HPLC purification, chemical purity was higher than 95 % and radi ochemical purity higher than 99 %. Specific activity was always higher than 222 GBq/mu mol (6 Ci/mu mol). The calculated log P is 4.28. Initial brain uptake in NMRI mice was 1.16 % ID (2 min) and decreased slowly afterwards ( 0.51 % ID (2 h)). 60 min p. i., the majority of the radioactivity in plasma and brain was present as (1) under bar. I-123, respectively 75.15 % and 96 .48 %.