A Mn^IIMn^III‐Peroxide Complex Capable of Aldehyde Deformylation

Abstract

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.

Spectroscopic Evidence for a Cobalt-Bound Peroxyhemiacetal Intermediate

“…30,31 These results demonstrated that the equilibrium lies to the left (Scheme 2). 32,33 The addition of an excess amount of 2-PPA shifts the equilibrium between 1 and 2 to the 2 side. The UV−vis spectrum of 2 could be obtained in the presence of a large excess of 2-PPA while the resulting green solution was maintained at 0 °C.…”

Photoactivatable Artificial Peroxidase System Using a Dimanganese Complex and Its Application to Light-Controlled Synthesis of Hydrogel

“…These results indicate a complete block of intrinsic peroxidase-like activity of Mn 2 (bpmp) by the introduction of PPG followed by inhibition of active dimetal-(hydro)peroxo intermediate formation. 19,20 In addition, under the varied conditions in which the raw Mn 2 (bpmp) was active, the activity of photocaged Mn 2 (bpmp) was not affected by changes in the surrounding temperature or pH without light irradiation, as shown in Figure 1c,d. It was confirmed that PPG in the photocaged Mn 2 (bpmp) was not cleaved in the absence of light and that the photocaged Mn 2 (bpmp) showed high stability.…”

“…18 A dimetal-(hydro)peroxo intermediate was demonstrated to be formed by the reaction of Mn 2 (bpmp) and H 2 O 2 . 19,20 Based on these results, we anticipated that the introduction of PPGs to the hydroxyl moiety of Mn 2 (bpmp) could mask the active sites and prevent active intermediate formation to completely block the intrinsic peroxidase-like activity and construct a photocaged Mn 2 (bpmp) system. In a photocaged Mn 2 (bpmp) system, the operating principle for activating the peroxidase-like activity relies on the irreversible cleavage of the PPG upon irradiation at a specific wavelength (uncaging), as shown in Scheme 1.…”

DFT Mechanistic Insights into Aldehyde Deformylations with Biomimetic Metal–Dioxygen Complexes: Distinct Mechanisms and Reaction Rules

“…Aldehyde deformylations are chemical reactions taking place in organisms during metabolism and biosynthesis. , These biochemical reactions are catalyzed by metalloenzymes such as cytochrome P450 and aldehyde decarbonylase (ADO). − By binding to molecular oxygen, the metal cofactors of the metalloenzymes form metal–dioxygen active cores that perform these reactions. − Inspired by these biological processes, much effort has been devoted to the study of small-molecule transition-metal–dioxygen complexes (denoted TM–O 2 complexes hereafter). − On the one hand, TM–O 2 complexes serve as biomimetic models to deeply understand the relevant biological processes like deformylations; on the other hand, studying the chemistry of TM–O 2 complexes could lead to the discovery of aerobic catalytic transformations. − The use of abundant molecular O 2 as an oxidant offers a green and sustainable approach to produce valuable chemical products.…”