The oxidation of cyclo-olefin by the S = 2 ground-state complex [FeIV(O)(TQA)(NCMe)]2

A Chemical Model of a TET Enzyme for Selective Oxidation of Hydroxymethyl Cytosine to Formyl Cytosine

Methylation/demethylation of cytosines in DNA is central to epigenetics, which plays crucial roles in the regulation of about half of all human genes. Although the methylation mechanism, which downregulates gene expression, has been sufficiently decoded; the demethylation pathway, which upregulates gene expression, still holds questions to be answered. Demethylation of 5-methylcytosine by ten-eleven translocation (TET) enzymes yields understudied but epigenetically relevant intermediates, 5-hydroxymethyl (5-hmC), 5-formyl (5-fC), and 5-carboxyl (5-caC) cytosines. Here we report an iron complex, Fe^IIITAML (TAML = tetraamido macrocyclic ligand), which can facilitate selective oxidation of 5-hmC to its oxidative derivatives by forming a high-valent Fe-oxo intermediate in the presence of H₂O₂ under physiologically relevant conditions. Detailed HPLC analyses supported by a wide reaction condition optimization for the 5-hmC → 5-fC oxidation provides us with a chemical model of the TET enzyme. This study shines light on future efforts for a better understanding of the roles of 5-hmC and the TET enzyme mechanism and potentially novel therapeutic methods.

Determining the inherent selectivity for carbon radical hydroxylation versus halogenation with high-spin oxoiron(iv)-halide complexes: a concerted rebound step

A synthetic iron model can process both halogenation and hydroxylation with vague selectivity, which is different from halogenase even though these structures are used for the simulation of halogenase. The key factor of the synthetic oxo-iron model mediated hydroxylation or the halogenation is still under debate. Herein density functional theory calculation is used to investigate the hydroxylation versus halogenation of propylene by the complex [Fe^IV(O)(TQA)(X)]⁺ (X = F, Cl, Br). Our results suggest that a concerted rebound mechanism (between the -X and the hydroxyl ligands after the hydrogen abstraction) leads to the formation of two different kinds of products.

DFT calculation for the hydroxylation versus halogenation of propylene by [Fe^IV(O)(TQA)X]⁺ (X = F, Cl and Br) reveals that after hydrogen abstraction, halogen and oxygen rebound reactions are a synergistic process.