Transamination and amine-exchange reactions in the system iron(II)-sodium pyruvate-aminomethylpyridine.  I.  Stoichiometry and reaction products

Holanda, Maria Isaura D.; Krumholz, P.; Chum, Helena L.

doi:10.1021/ic50158a031

Cited by 18 publications

(12 citation statements)

References 24 publications

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“…One drawback, however, is that Schiff base compounds are susceptible to hydrolysis and transamination by nucleophiles due to the presence of an imine group (C=N). 11 The role of the metal ion as catalyst in the hydrolysis and transamination of SB ligands, where the transamination reaction is equilibrium controlled, and the excess of exchanging amine favors the reaction, is well documented. 12, 13 In a recent study, the uranyl ion has been demonstrated to catalyze the reversible transamination of 2-methylalanine with pyridoxal (Vitamin B 6 ) yielding [(UO 2 PmHpyr) 3 (l 3 -O)]Cl•3H 2 O (PmHpyr = pyridoxaminylpiruvate anion).…”

Section: Introductionmentioning

confidence: 99%

Hydroxy- and alkoxy-bridged dinuclear uranyl–Schiff base complexes: hydrolysis, transamination and extraction studies

et al. 2008

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The reaction of uranyl nitrate with 1,3-bis(salicylideneamino)-2-propanol (H(3)L1) and 1,3-bis(3,5-di-tert-butylsalicylideneamino)-2-propanol (H(3)L2) in the presence of triethylamine (Et(3)N) yielded hydroxy- and alkoxy-bridged dinuclear complexes; [(UO(2))(2)(L1)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)) and [(UO(2))(2)(L2)(OH)(MeOH)(2)].(MeOH)(2) (.(MeOH)(2)). The crystal structures of .(DMF)(2) and .(DMF)(2) exhibit an unsymmetrical central U(2)O(2) core involving bridging alkoxy- and hydroxy-oxygen atoms. The geometry around the uranium center in .(DMF)(2) and .(DMF)(2) is that of a distorted pentagonal bipyramid with the solvent molecule occupying the fifth coordination site. The flexible nature of the ligand backbone is more pronounced in .(DMF)(2) compared to .(DMF)(2), yielding two molecules per unit cell in different conformations. Under similar reaction conditions, using ethylenediamine as a base, the respective Salen-based uranyl compounds, [UO(2)(Salen)(MeOH)] () and [UO(2)(Bu(t)(2)-Salen)(MeOH)] () are obtained due to transamination of the ligand backbone. Complexes .(MeOH)(2) and .(MeOH)(2) when reacted with an excess of ethylenediamine failed to yield the respective Salen-based complexes, and , respectively. The new compounds have been characterized using solution (NMR and UV-Vis) and solid-state (IR, X-ray crystallography) techniques. Hydrolysis of .(MeOH)(2) and .(MeOH)(2) in the pH range 1-14 was studied using UV-Vis spectroscopy and compared with the hydrolysis of and [UO(2)(Salophen)(MeOH)] (). A two-phase extraction study suggests quantitative removal of uranyl ions from the aqueous phase at higher pH conditions.

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Section: Introductionmentioning

confidence: 99%

Hydroxy- and alkoxy-bridged dinuclear uranyl–Schiff base complexes: hydrolysis, transamination and extraction studies

et al. 2008

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“…5,6 In a transamination reaction, the stronger base replaces the weaker base; in this case, the imine group (CLN) of the SB is susceptible to hydrolysis by nucleophiles. 7 Metal ion catalysis in transamination reactions of SB compounds is well documented. 8,9 With transition metal ions including Cu 2+ , Ni 2+ , Zn 2+ and Fe 2+ , the transamination reaction is equilibrium controlled, and the excess of exchanging amine favors the reaction.…”

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confidence: 99%

Uranyl stabilized Schiff base complex

2007

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“…However in the present case, there is no significant difference in coordination geometry of 1 vs. 2, nor is there any substantial difference in ligand-field strength of the three ligands 1, 2 and 4, based on interpretation of the electronic spectra of the Ni(II) and Cu(II) complexes [9,18]. Although numerous examples of iron-mediated oxidative dehydrogenation are known, more study of the mechanistic aspects is needed [19][20][21][22]. By comparison greater progress has been made understanding the oxidative dehydrogenation of Ru and Os complexes, possibly because the reaction mediated by these metals is slower [13,[23][24][25][26][27].…”

Section: Iron-mediated Oxidative Dehydrogenationmentioning

confidence: 79%

Influence of ligand structure on Fe(II) spin-state and redox rate in cytotoxic tripodal chelators

Childers

Cho

Regino

et al. 2008

Journal of Inorganic Biochemistry

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The Fe coordination chemistry of several tripodal aminopyridyl hexadentate chelators is reported along with cytotoxicity toward cultured Hela cells. The chelators are based on cis, cis-1,3,5-triaminocyclohexane (tach) with three pendant -CH2-2-pyridyl groups where 2-pyridyl is R-substituted thus are named tach-x-Rpyr where x=3, R=Me; x=3, R=MeO; x=6; R=Me. The structures of [Fe(tach-3-Mepyr)]Cl2 and [Fe(tach-3-MeOpyr)](FeCl4) are reported and their metric parameters indicate strongly bound, low-spin Fe(II). The structure of [Fe(tach-6-Mepyr)](ClO4)2 implies steric effects of 6-Me groups push donor Npy's away so one Fe-Npy bond is substantially longer at 2.380(3)A vs. 2.228(3)A for the others, and Fe(II) in the high-spin-state. Accordingly, anions X(-)=Cl or SCN afford [Fe(tach-6-Mepyr)(X)]+ from [Fe(tach-6-Mepyr)]2+ (UV-vis spectroscopy). Consistent with a biological cytotoxicity involving Fe chelation, chelators of low-spin Fe(II) have greater toxicity in the order [IC50(72 h) is in parentheses then the spin-state SS=H (high) or L (low)]: tachpyr=tach-3-Mepyr (6 microM, SS=L) greater, similar tach-3-MeOpyr (12microM, SS=L)>>tach-6-Mepyr (>200 microM, SS=H). Iron-mediated oxidative dehydrogenation with O2 oxidant removes hydrogens from coordinated nitrogen and the adjacent CH2, converting aqueous [Fe(tach-3-Rpyr)]2+ (R=H, Me and MeO) into a mix of low-spin imino- and aminopyridyl-armed complexes, but [Fe(tach-6-Mepyr)]2+ does not react (NMR and ESI-MS spectroscopies). The difference of IC(50) for chelators at different time points (delta IC50=[IC50(24h)-IC50(72 h)]) is used to compare rate of cytotoxic action to qualitative rate of oxidation in the Fe-bound chelator, giving the order, from rapid to slow oxidation and cell killing of: [Fe(tach-3-Mepyr)]2+ (delta IC50=5 microM)>[Fe(tachpyr)]2+ (delta IC50=16 microM)>[Fe(tach-3-MeOpyr)]2+ (delta IC50=118 microM). Thus, those chelators whose Fe(II) complexes undergo rapid oxidation kill cells faster, and those that bind Fe(II) as low-spin are far more cytotoxic.

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Transamination and amine-exchange reactions in the system iron(II)-sodium pyruvate-aminomethylpyridine. I. Stoichiometry and reaction products

Cited by 18 publications

References 24 publications

Hydroxy- and alkoxy-bridged dinuclear uranyl–Schiff base complexes: hydrolysis, transamination and extraction studies

Hydroxy- and alkoxy-bridged dinuclear uranyl–Schiff base complexes: hydrolysis, transamination and extraction studies

Uranyl stabilized Schiff base complex

Influence of ligand structure on Fe(II) spin-state and redox rate in cytotoxic tripodal chelators

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