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Tsoukalas C, Pirmettis I, Patsis G, Pelecanou M, Bodo K, Raptopoulou CP, Terzis A, Papadopoulos M, Chiotellis E: Novel oxorhenium and oxotechnetium MO (NS)(S) 2 complexes in the development of 5-HT1A receptor imaging agents. J Inorg Biochem. 2003 Jan 15;93(3-4):213-20.
The [NS][S](2) mixed-ligand system was applied to synthesize oxorhenium and oxotechnetium complexes of the general formula MO (o-CH (3) OC (6) H (4) N (CH (2) CH (2))(2) NCH (2) CH (2) S)(p-CH (3) C (6) H (4) S)(2) (M=Re in 1, M=(99) Tc in 2, and M=(99m) Tc in 3). The bidentate [NS] ligand includes the 1-(2-methoxyphenyl) piperazine moiety which is a fragment of the true 5-HT (1A) antagonist WAY 100635. The oxorhenium complex 1 was prepared by a ligand exchange reaction using ReOCl (3)(PPh (3))(2) as precursor while [Bu (4) N][(99) TcOCl (4)] and (99) Tc-gluconate were used as precursors in the synthesis of the oxotechnetium-99 complex 2. Both complexes were characterized by elemental analysis and spectroscopic methods. Crystallographic analysis of 1 showed that the rhenium coordination geometry is trigonal bipyramidal. The basal plane of the trigonal bipyramid is defined by the oxo group and two sulphur atoms, one belonging to the [NS] ligand and the other to an aromatic thiol, while the apical positions are occupied by the nitrogen of the [NS] ligand and the sulphur of the second aromatic thiol. The oxotechnetium-99 complex 2 has almost identical unit cell parameters to those of the oxorhenium complex 1 indicating, in combination with the other analytical data, that the complexes are isostructural. The binding affinity of the oxorhenium complex 1 for the 5-HT (1A) receptor subtype was determined in rat brain hippocampal preparations (IC (50)=106 nM). The oxotechnetium-99m complex 3 was prepared by a ligand exchange reaction using (99m) Tc-glucoheptonate as the precursor. Its structure was established by comparative HPLC studies using the oxotechnetium-99 complex 2 as a reference. Complex 3 was administered by intravenous injection in rats. At 2 min post injection, 0.153% of the injected dose per gram of tissue was measured in rat brain. |
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