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, FeIIITAML (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.

ortho-Oxygenative 1,2-Difunctionalization of Diarylalkynes under Merged Gold/Organophotoredox Relay Catalysis.

Reported herein is an ortho-oxygenative 1,2-difunctionalization of diarylalkynes under merged gold/organophotoredox catalysis to access highly functionalized 2-(2-hydroxyaryl)-2-alkoxy-1-arylethan-1-ones. Detailed mechanistic studies suggested a relay process, initiating with gold-catalyzed hydroalkoxylation of alkynes, to generate enol-ether followed by a key formal [4+2]-cycloaddition reaction. The successful application of the present methodology was also shown for the synthesis of benzofurans.