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Selective Functionalisation of 5-Methylcytosine by Organic Photoredox Catalysis.

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Goodman, Jonathan M  ORCID logo
Balasubramanian, Shankar  ORCID logo


The epigenetic modification 5-methylcytosine plays a vital role in development, cell specific gene expression and disease states. The selective chemical modification of the 5-methylcytosine methyl group is challenging. Currently, no such chemistry exists. Direct functionalisation of 5-methylcytosine would improve the detection and study of this epigenetic feature. We report a xanthone-photosensitised process that introduces a 4-pyridine modification at a C(sp3)-H bond in the methyl group of 5-methylcytosine. We propose a reaction mechanism for this type of reaction based on density functional calculations and apply transition state analysis to rationalise differences in observed reaction efficiencies between cyanopyridine derivatives. The reaction is initiated by single electron oxidation of 5-methylcytosine followed by deprotonation to generate the methyl group radical. Cross coupling of the methyl radical with 4-cyanopyridine installs a 4-pyridine label at 5-methylcytosine. We demonstrate use of the pyridination reaction to enrich 5-methylcytosine-containing ribonucleic acid.


Funder: Herchel Smith Fund

Funder: Trinity College, University of Cambridge; Id:

Funder: Krishnan-Ang Studentships Programme


C−H Functionalization, Nucleic Acids, Photocatalysis, Radicals, Reaction Mechanisms

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Angew Chem Weinheim Bergstr Ger

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Wellcome Trust (209441/Z/17/Z)