Novel optically-active bis(amino acid) ligands and their complexation with gadolinium
作者:Hiroyuki Miyake、Masaaki Watanabe、Makoto Takemura、Takayuki Hasegawa、Yoshitane Kojima、Michiko B. Inoue、Motomichi Inoue、Quintus Fernando
DOI:10.1039/b108024p
日期:2002.3.8
A condensation reaction of glyoxal with (S)-histidine and (S)-aspartic acid yielded a new optically-active bis(amino acid) ligand, N-[(S)-1-carboxy-2-(imidazol-4-yl)ethyl]-N′-[(S)-1,2-dicarboxyethyl]ethylenediamine. Two bis(amino acid) ligands with picolyl (pyridylmethyl) groups were synthesized by condensation reactions of glyoxal with the picolyl derivative of (S)-histidine and that of (S)-aspartic acid: the obtained ligands are N,N′-bis(2-pyridylmethyl)-N-[(S)-1-carboxy-2-(imidazol-4-yl)ethyl]-N′-[(S)-1,2-dicarboxyethyl]ethylenediamine and N,N′-bis(2-pyridylmethyl)-N,N′-bis[(S)-1-carboxy-2-(imidazol-4-yl)ethyl]ethylenediamine. The protonation constants of these ligands were determined by potentiometry, and the corresponding protonation sites were located on the basis of 1H NMR spectra obtained
at different pD values. The formation constants of the Gd3+ complexes were determined by potentiometric titrations, and the NMR relaxivities r1 and r2 by the measurements of the NMR relaxation times.
由乙二醛与(S)-组氨酸和(S)-天冬氨酸的缩合反应得到一种新的光学活性双(氨基酸)配体,N-[(S)-1-羧基-2-(咪唑-4-基)乙基]-N'-[(S)-1,2-二羧基乙基]乙二胺。由乙二醛与(S)-组氨酸的吡啶甲基衍生物和(S)-天冬氨酸的吡啶甲基衍生物缩合反应合成得到两种带有吡啶甲基基团的双(氨基酸)配体:所得到的配体为N,N'-双(2-吡啶甲基)-N-[(S)-1-羧基-2-(咪唑-4-基)乙基]-N'-[(S)-1,2-二羧基乙基]乙二胺和N,N'-双(2-吡啶甲基)-N,N'-双[(S)-1-羧基-2-(咪唑-4-基)乙基]乙二胺。通过电位法确定这些配体的质子化常数,并通过在不同pD值下获得的1H NMR谱确定相应的质子化位点。通过电位滴定法确定Gd3+配合物的形成常数,并通过NMR弛豫时间的测量确定NMR弛豫率r1和r2。