N-Hydroxyamide-Containing Heterocycles. Part 4. Synthesis and FeIII-Chelating Properties of Novel Hexadentate Ligands Composed of N-Hydroxy-2(1H)-Pyrazinone, Amino Acid Residues, and Tris(2-aminoethyl)amine
作者:Junko Ohkanda、Akira Katoh
DOI:10.1021/jo00111a015
日期:1995.3
Synthesis of novel hexadentate ligands (3-HOPR(X); X = Me and Bu(i)) composed of N-hydroxy-2(1H)-pyrazinone, amino acids, and tris(2-aminoethyl)amine, and their Fe-III-chelating properties are described. N-(Benzyloxy)-2(VF)-pyrazinone (6) bearing the carboxyl group at C-3 position of the pyrazinone ring was synthesized from L-glutamic acid vip five steps. The consecutive coupling of 6 with amino acids and tris(2-aminoethyl)amine, followed by the deprotection of the O-benzyl group, afforded target compounds (3-HOPR(X)). UV-vis spectral data of the 1:1 molar mixture of 3-HOPR(X) and Fe-III in aqueous solution indicated the formation of intramolecular 1:3 Fe-III complex to the hydroxamate units. The relative stability constants (log K 21-22) of the complexes were influenced by the side chains of L-amino acid residues. Further, the absolute configuration around Fe-III was dramatically changed, viz., Fe(3-opr(Me)) exists predominantly in the Lambda-cis configuration, while Fe(3-opr(Bu(i))) exist in the Delta-cis in water. From the Fe-III removal experiment of 3-HOPR(X) from transferrin at pH 7.4, it was concluded that 3-HOPR(X) was a more effective Fe-III removal agent than the naturally occurring siderophore, desferrioxamine B.