Evaluation of two chelators for labelling a PNA monomer with the fac-[Tc(CO)3] moiety |
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Authors: | Catarina Xavier Isabel Santos Roger Alberto |
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Affiliation: | a Departamento de Química, Instituto Tecnológico e Nuclear, Estrada Nacional 10, 2686-953 Sacavém, Portugal b Institute of Inorganic Chemistry, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland |
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Abstract: | A PNA monomer containing thymine as nucleobase (1) was synthesized, characterized and coupled to the pyrazolyl containing ligand 3,5-Me2pz(CH2)2N((CH2)3COOH)(CH2)2NHBoc (2) and to a modified cysteine S-(carboxymethyl-pentafluorphenyl)-N-[(trifluor)carbonyl]-l-cysteine methyl ester (3) yielding the bifunctional chelators 6 and 7, respectively. Reactions of 6 and 7 with the Re(I) tricarbonyl starting material [Re(CO)3(H2O)3]Br afforded the complexes fac-[Re(CO)3(κ3-6)]+ (8) and fac-[Re(CO)3(κ3-7)] (9), respectively. The identity of 8 and 9 has been established based on IR spectroscopy, elemental analysis, ESI-MS spectrometry and HPLC. The multinuclear NMR spectroscopy (1H, 13C, g-COSY, g-HSQC) has also been very informative in the case of complex 8, showing the presence of rotamers in solution. For 9 the NMR spectrum was too complex due to the presence of rotamers and diastereoisomers. The radioactive congeners of complexes 8 and 9, fac-[99mTc(CO)3(κ3-6)]+ (8a) and fac-[99mTc(CO)3(κ3-7)] (9a), have been prepared by reacting the precursor fac-[99mTc(CO)3(H2O)3]+ with the corresponding ligands being their identity established by comparing their HPLC chromatograms with the HPLC of the rhenium surrogates. |
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Keywords: | PNA Antisense Tricarbonyl Technetium Rhenium |
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