A MnIIMnIII‐Peroxide Complex Capable of Aldehyde Deformylation

Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn2 RNRs superoxide (O2.−) was postulated to react with the MnII2 core to yield a MnIIMnIII‐peroxide moiety. The reactivity of complex 1 ([MnII2(O2CCH3)2(BPMP)](ClO4), where HBPMP=2,6‐bis{[(bis(2‐pyridylme...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2019-04, Vol.58 (17), p.5718-5722
Main Authors: Magherusan, Adriana M., Kal, Subhasree, Nelis, Daniel N., Doyle, Lorna M., Farquhar, Erik R., Que, Lawrence, McDonald, Aidan R.
Format: Article
Language:English
Subjects:
Absorption
Absorption spectra
aldehyde deformylation
Catalysis
Deformation mechanisms
Deoxyribonucleic acid
DNA
DNA biosynthesis
Electron paramagnetic resonance
Intermediates
Mass spectrometry
Mass spectroscopy
MnIIMnIII-peroxide
nucleophilic reactivity
Peroxide
Peroxides
Reductases
ribonucleotide reductases
Superoxide
superoxide activation
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Summary:Ribonucleotide reductases (RNRs) are essential enzymes required for DNA synthesis. In class Ib Mn2 RNRs superoxide (O2.−) was postulated to react with the MnII2 core to yield a MnIIMnIII‐peroxide moiety. The reactivity of complex 1 ([MnII2(O2CCH3)2(BPMP)](ClO4), where HBPMP=2,6‐bis{[(bis(2‐pyridylmethyl)amino]methyl}‐4‐methylphenol) towards O2.− was investigated at −90 °C, generating a metastable species, 2. The electronic absorption spectrum of 2 displayed features (λmax=440, 590 nm) characteristic of a MnIIMnIII‐peroxide species, representing just the second example of such. Electron paramagnetic resonance and X‐ray absorption spectroscopies, and mass spectrometry supported the formulation of 2 as a MnIIMnIII‐peroxide complex. Unlike all other previously reported Mn2‐peroxides, which were unreactive, 2 proved to be a capable oxidant in aldehyde deformylation. Our studies provide insight into the mechanism of O2‐activation in Class Ib Mn2 RNRs, and the highly reactive intermediates in their catalytic cycle. Nucleophilic reactivity: The reaction of a MnII2 complex with superoxide yielded a MnIIMnIII‐peroxide complex which mimics intermediates in class Ib Mn2 ribonucleotide reductases. The MnIIMnIII‐peroxide species displayed an unexpected nucleophilic character in aldehyde deformylation.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201900717