ISBN: 978-83-60043-10-3 - eurobic9

Eurobic9, 2-6 September, 2008, Wrocław, Poland
P55. Fac-Tc(Co)3 + And Fac-Re(Co)3 + Complexed by Histidine Derivatives -
Potential Precursors of Radiopharmaceuticals
L. Fuks a , E. Gniazdowska a , D. Papagiannopoulou b , P. Kozminski a , M. Papadopoulos c ,
M. Pelecanou c , I. Pirmettis c , C. Raptopoulou c , N. Sadlej-Sosnowska d , C. Tsoukalas c
a Institute of Nuclear Chemistry and Technology, Warsaw, Poland
e-mail: egniazdo@ichtj.waw.pl
b School of Pharmacy, Aristotle University, Thessaloniki, Greece
c National Centre of Scientific Research "DEMOKRITOS, Athens, Greece
d National Medicines Institute, Warsaw, Poland
Studies on the Tc(CO)3 + and Re(CO)3 + complexes in the last years have received special momentum since they
give chance to prepare a series of novel radiopharmaceuticals [1]. Kinetic inertness of the tricarbonylrhenium(I)
core containing cation of the d6 electronic configuration gives ground for the interest in its complexes, especially
those obtained by substitution of two or three labile water molecules by bi- or tridentate chelating ligands.
The aim of our studies is to find novel ligands, which form stable complexes with Tc(CO)3 + and Re(CO)3 + , that
after conjugation to a biomolecule can be used for the development of 2 nd generation targeted
radiopharmaceuticals. In the present paper we describe the synthesis and characterization of novel
[Tc/Re(SNO)(CO)3] complexes where SNO is the 4-methoxybenzyl derivative of the
3-(1H-imidazol-4-yl)-2-mercaptopropanoic acid - a tridentate SNO ligand, synthesized from L-histidine.
The IR spectrum of the [Re(SNO)(CO)3] complex indicates the characteristic bands of three facially coordinated
CO groups. 1 H NMR studies show typical pattern of diasterotopic protons of the SNO backbone after
complexation. X ray analysis of the complex shows octahedral structure with SNO ligand coordinated in a
tripodal fashion. The presence of complex diasteromers was also explored by quantum chemical calculations that
resulted in two potential configurations. Quantum chemical calculations have shown that they can be related to
different complex structures with comparable energy (∆ ≈ 0.3 and 0.4 kcal/mol for Tc I and Re I respectively).
Successful labeling of the SNO ligand with suitable fac-[ 99m Tc/ 188 Re(CO)3] + cores led to the formation of stable
complexes at tracer level, indicating the suitability of this system for the development of novel
radiopharmaceuticals.
Fig.: cis- and trans-configurations (left and right, respectively) of ligand complexing the Re I (CO)3 + moiety.
Conclusion: 3-(1H-imidazol-4-yl)-2-[(4-methoxybenzyl)thio]propanoic acid is a potent chelator for the fac-
[ 99m Tc/ 188 Re(CO)3] + core and it could be applied for the design of novel bioactive fac-[ 99m Tc/ 188 Re(SNO)(CO)3]
complexes - potential diagnostic or therapeutic radiopharmaceuticals, respectively.
Acknowledgement
Part of the work was performed within the Maria Curie Transfer of Knowledge training contract MTKD-CT-
2004-509224 (POL-RAD-PHARM: Chemical studies for design and production of new radiopharmaceuticals).
References:
[1] U. Abram, R Alberto, Technetium and Rhenium - Coordination Chemistry and Nuclear Medical
Applications. J. Brazil. Chem. Soc., 2006, 17(8), 1486-1500.
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