Synthesis, characterization and relaxivity of dimeric DTPA-gadonium (III) complexes with long chain alkyl esters of L-lysine

To look for new MRI (magnetic resonance imaging) contrast agents with higher relaxivity as well as liver-selecsivity, four novel ester-amino ligands were synthesized by bis-acylation of octadecanyl, hexadecanyl, tetradecanyl and dedecanyl L-lysine with diethylenetriaminepentaacetic acid mono-anhydride (DTPA-MA), respectively. The corresponding dimeric Gd(M) complexes were gained by the reaction of these ligands with GdCl(3) center dot 6H(2)O. All ligands and complexes were characterized by FTIR, (1)H NMR and elemental analysis. The longitudinal relaxation time (T(1)) was measured, and relevant longitudinal relaxivity (R(1)) of these neatral binuclear Gd (III) complexes is: 6.48, 6.02, 5.76 and 5.68 L . mmol(-1) . s(-1), respectively, and all are higher than that of Gd-DTPA (4.98 L . mmol(-1) . s(-1)) (300 MHz).