Synthesis and biological evaluation of .sup.99mTc labeled aryl piperazine derivatives as cerebral radiotracers

The aim of this study is to develop cerebral radiotracers for central nervous system receptors imaging. The synthesis, characterization and biological evaluation of two aryl piperazine .sup.99mTc-radiocomplexes based on the piano stool motif [CpM(CO.sub.3)] (Cp = cyclopentadienyl, M = .sup.99mTc/Re) is reported. The .sup.99mTc-radiocomplexes were obtained quickly (time < 5 min) with high radiochemical yields. The .sup.99mTc-radiocomplexes characterized by high performance liquid chromatography comparison with the rhenium surrogates have both a suitable lipophilicity and are able to cross the blood brain barrier with 0.43 ± 0.05 and 1.96 ± 0.06% ID/g of brain uptake, at 10 min post injection.