Bio-inspired amino acid oxidation by a non-heme iron catalyst.

This study reports the kinetics and mechanism of Fe(III)-catalyzed oxidative decarboxylation and deamination of a series of acyclic (α-aminoisobutyric acid, α-(methylamino)isobutyric acid, alanine, norvaline, and 2-aminobutyric acid) and cyclic (1-aminocyclopropane-1-carboxylic acid, 1-amino-1-cyclobutanecarboxylic acid, 1-aminocyclopentanecarboxylic acid, and 1-aminocyclohexanecarboxylicacid) amino acids using hydrogen peroxide, t-butyl hydroperoxide, iodosylbenzene, m-chloroperbenzoic acid, and peroxomonosulphate as oxidant in 75% DMF-25% water solvent mixture. Model complex [Fe(IV)O(SALEN)](•+) (SALENH2: N,N'-bis(salicylidene)ethylenediamine) was generated by the reaction of Fe(III)(SALEN)Cl and H2O2 in CH3CN at 278 K as reported earlier. This method provided us high-valent oxoiron species, stable enough to ensure the direct observation of the reaction with amino acids.

An Iron(II)(1,3-bis(2'-pyridylimino)isoindoline) Complex as a Catalyst for Substrate Oxidation with H2O2. Evidence for a Transient Peroxodiiron(III) Species.

The complex [Fe(indH)(solvent)3](ClO4)2 (1) has been isolated from the reaction of equimolar amounts of 1,3-bis(2'-pyridylimino)isoindoline (indH) and Fe(ClO4)2 in acetonitrile and characterized by X-ray crystallography and several spectroscopic techniques. It is a suitable catalyst for the oxidation of thioanisoles and benzyl alcohols with H2O2 as the oxidant. Hammett correlations and kinetic isotope effect experiments support the involvement of an electrophilic metal-based oxidant. A metastable green species (2) is observed when 1 is reacted with H2O2 at -40 °C, which has been characterized to have a FeIII(µ-O)(µ-O2)FeIII core on the basis of UV-Vis, electron paramagnetic resonance, resonance Raman, and X-ray absorption spectroscopic data.

Bio-inspired flavonol and quinolone dioxygenation by a non-heme iron catalyst modeling the action of flavonol and 3-hydroxy-4(1H)-quinolone 2,4-dioxygenases.

The mononuclear complex, Fe(III)(O-bs)(salen) (salenH(2)=1,6-bis(2-hydroxyphenyl)-2,5-diaza-hexa-1,5-diene; O-bsH=O-benzoylsalicylic acid) was synthesized as synthetic enzyme-depside complex, and characterized by spectroscopic methods and X-ray crystal analysis. The dioxygenation of flavonol (flaH) and 3-hydroxy-4-quinolone (quinH(2)) derivatives in the presence of catalytic amounts of Fe(III)(O-bs)(salen) results in the oxidative cleavage of the heterocyclic ring to give the corresponding O-benzoylsalicylic and anthranilic acid derivatives with concomitant release of carbon monoxide. These reactions can be regarded as biomimetic functional models with relevance to the iron-containing flavonol and the cofactor-independent 3-hydroxy-4(1H)-quinolone 2,4-dioxygenases.

Bio-inspired amino acid oxidation by a non-heme iron catalyst modeling the action of 1-aminocyclopropane-1-carboxylic acid oxidase.

In this communication we describe the first example of a biomimetic mononuclear iron complex, [Fe(III)(Salen)Cl] (Salen = N,N'-bis(salicylidene)-ethylenediaminato), that highly selectively and efficiently catalyzes the oxidation of 1-aminocyclopropane-1-carboxylic acid (ACCH), α-aminoisobutyric acid (AIBH), and alanine (ALAH) to ethylene or the corresponding carbonyl compounds, mimicking the action of the non-heme iron enzyme 1-aminocyclopropane-1-carboxylic acid oxidase (ACCO).

One metal-two pathways to the carboxylate-enhanced, iron-containing quercetinase mimics.

Mononuclear iron(iii) flavonolate was synthesized as synthetic enzyme-substrate complex, and its direct and carboxylate-enhanced dioxygenation as biomimetic functional models with relevance to flavonol 2,4-dioxygenase are briefly described.

Catechol oxidase and phenoxazinone synthase activity of a manganese(II) isoindoline complex.

The mononuclear [Mn(6'Me(2)indH)(H(2)O)(2)(CH(3)CN)](ClO(4))(2) (6'Me(2)indH: 1,3-bis(6'-methyl-2'-pyridylimino)isoindoline) complex has been prepared and characterized by various techniques such as elemental analysis, IR, UV-visible and ESR spectroscopy. The title compound was suitable as catalyst for the catalytic oxidation of 3,5-di-tert-butylcatechol (3,5-DTBCH(2)) to 3,5-di-tert-butyl-1,2-benzoquinone (3,5-DTBQ) (catecholase activity), and o-aminophenol (OAPH) to 2-aminophenoxazine-3-one (APX) (phenoxazinone synthase activity) with dioxygen at ambient condition in good yields. Kinetic measurements revealed first-order dependence on the catalyst and dioxygen concentration and saturation type behavior with respect to the corresponding substrate. It was also found that the added triethylamine in both systems accelerates the reaction.

Manganese and iron flavonolates as flavonol 2,4-dioxygenase mimics.

Mononuclear manganese(II) and iron(III) flavonolates were synthesized as synthetic enzyme-substrate complexes, and their oxygenation reactions as biomimetic functional models with relevance to flavonol 2,4-dioxygenases are briefly described.