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- Title
Synthesis and Characterization of Various Benzyl Diethylenetriaminepentaacetic Acids (dtpa) and Their Paramagnetic Complexes, Potential Contrast Agents for Magnetic Resonance Imaging.
- Authors
Laurent, Sophie; Vander Elst, Luce; Houzé, Sylvain; Guérit, Nathalie; Muller, Robert N.
- Abstract
Four derivatives of diethylenetriaminepentaacetic acid (=3,6,9-tris(carboxymethyl)-3,6,9-triazaundecanedioic acid (H5dtpa)), potential contrast agents for magnetic resonance imaging (MRI), carrying benzyl groups at various positions of the parent structure were synthesized and characterized by a thorough multinuclear NMR study, i.e., the ( S)- and ( R)-stereoisomers 1a and 1b of 4-benzyl-3,6,9-tris(carboxymethyl)-3,6,9-triazaundecanedioic acid (H5[( S)-(4-Bz)dtpa] and H5[( R)-(4-Bz)dtpa], the diamide derivative N, N″-bis[(benzylcarbamoyl)methyl]diethylenetriamine- N, N′, N″-triacetic acid (=3,9-bis[2-(benzylamino)-2-oxoethyl]-6-(carboxymethyl)-3,6,9-triazaundecanedioic acid; H3[dtpa(BzA)2]; 2), and the diester derivative N, N″-bis{[(benzyloxy)carbonyl]methyl}diethylenetriamine- N, N′, N″-triacetic acid (=3,9-bis[2-(benzyloxy)-2-oxoethyl]-6-(carboxymethyl)-3,6,9-triazaundecanedioic acid; H3[dtpa(BzE)2]; 3). From the 17O-NMR chemical shift of H2O induced by their dysprosium complexes with ligands 1 - 3, it was concluded that only one H2O molecule is contained in the first coordination sphere of these lanthanide complexes. The rotational correlation times ( τR) of the complexes were estimated from the 2H-NMR longitudinal relaxation rate of the deuterated diamagnetic lanthanum complexes. The exchange time of the coordinated H2O molecule ( τM) was studied through the temperature dependence of the 17O-NMR transverse relaxation rate. As compared to [Gd(dtpa)]2−, the H2O-exchange rate is faster for [Gd{( S)-(4-Bz)dtpa}]2− and [Gd{( R)-(4-Bz)dtpa}]2−-, slower for [Gd{dtpa(BzA)2}], and almost identical for [Gd{dtpa(BzE)2}]. The analysis of the 1H-relaxivity of the gadolinium complexes recorded from 0.02 to 300 MHz established that i) the relaxivity of [Gd{dtpa(BzE)2}] is similar to that of [Gd(dtpa)]2−, ii) the slightly slower molecular rotation of [Gd{dtpa(BzA)2}] induces a mild enhancement of its relaxivity, and iii) the marked increase of relaxivity of [Gd{( S)-(4-Bz)dtpa}]2− and [Gd{( R)-(4-Bz)dtpa}]2− mainly results from an apparently shorter distance between the gadolinium ion and the H2O protons of the coordinated H2O molecule.
- Publication
Helvetica Chimica Acta, 2000, Vol 83, Issue 2, p394
- ISSN
0018-019X
- Publication type
Article
- DOI
10.1002/(SICI)1522-2675(20000216)83:2<394::AID-HLCA394>3.0.CO;2-B