- C3-symmetric ferrichrome-mimicking Fe3+-complexes containing the 1-hydroxypyrimidinone Fe3+-binding moieties based on α-cyclodextrin: Helicities in solvent environments
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Two homologous C3-symmetric ferrichrome mimics, La and Lb, equipped with three 1-hydroxypyrimidinone terminals for receiving an Fe3+ ion have been designed and synthesized; the side chains of La and Lb, which include dimethylene and pentamethylene spacers, respectively, are anchored to the narrower rim of the αcyclodextrin framework through an amide linkage. The 1:1 Fe3+-complexes of La and Lb provide strong circular dichroic exciton coupling of negative and positive signs at 480 nm, showing δ- and ∧helices, respectively, in polar aprotic solvents such as dimethylformamide and dimethyl sulfoxide. The magnetic of the signals increases with the increasing hydrogen-bond accepting ability of the solvent. It is inferred, therefore, that hydrogen-bonding interactions of the linker amide N-H groups with the solvent play a primary role in inducing a helicity within aprotic solvents. The mechanisms of the helicity inductions are discussed. Meanwhile, the signals for La are still negative, but weak in alcohols and water. However, the signal sign for Lb having the relatively flexible spacers depends on the nature of alcohols, and no CD signal was observed in water.
- Masuda, Takeshi,Hayashi, Jun-Ichiro,Tamagaki, Seizo
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p. 161 - 167
(2007/10/03)
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- Novel Iron Sequestering Agents: Synthesis and Iron-Chelating Properties of Hexadentate Ligands Composed of 1-Hydroxy-2(1H)-pyrimidinone, ω-Amino Carboxylic Acid, and Tris(2-aminoethyl)amine
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Novel heterocyclic hexadentate ligands (3HOPYn: n = 5-7), in which three units of 1-hydroxy-2(1H)-pyrimidinone are linked to tris(2-aminoethyl)amine through an amide bond by an alkyl chain, were synthesized, and their iron-chelating properties were investigated. The stability of their iron complexes (25 to 27 in log K) was significantly larger than that of pyrazinone-containing ligands by virtue of higher pKa values. On kinetic evaluation of iron removal from human transferrin, 3HOPY5 showed remarkable efficiency over five times as much as commercially available desferrioxamine B. The conformational analysis of the corresponding Ga(III) complex of Fe(opy5) by 1H NMR and by MM and MD calculations are also discussed.
- Ohkanda, Junko,Kamitani, Jun,Tokumitsu, Takeshi,Hida, Yoko,Konakahara, Takeo,Katoh, Akira
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p. 3618 - 3624
(2007/10/03)
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