scholarly journals Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

2021 ◽  
Author(s):  
Mao Cai ◽  
Kaini Xu ◽  
Yuze Li ◽  
Zongxiu Nie ◽  
Long Zhang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Primary Amine ◽  
Cooperative Catalysis

scholarly journals Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

2020 ◽  
Author(s):  
Mao Cai ◽  
Kaini Xu ◽  
Yuze Li ◽  
zongxiu nie ◽  
Long Zhang ◽  
...  
Keyword(s):  
Primary Amine ◽  
Catalytic Activation ◽  
Cooperative Catalysis ◽  
New Strategy ◽  
Yin And Yang ◽  
Dual Catalysis ◽  
Chiral Esters ◽  
High Stereoselectivity ◽  
Operational Simplicity

<p>Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric <i>α</i>-hydroxylation with H<sub>2</sub>O<sub>2</sub>. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H<sub>2</sub>O<sub>2</sub> <i>via</i> an oxaziridine intermediate derived from<i> in-situ</i> generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of <i>β</i>-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective <i>α</i>-hydroxylation of a broad range of <i>β</i>-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H<sub>2</sub>O<sub>2</sub> and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.</p>

scholarly journals Chiral Primary Amine/Ketone Cooperative Catalysis for Asymmetric α-Hydroxylation with Hydrogen Peroxide

2020 ◽  
Author(s):  
Mao Cai ◽  
Kaini Xu ◽  
Yuze Li ◽  
zongxiu nie ◽  
Long Zhang ◽  
...  
Keyword(s):  
Primary Amine ◽  
Catalytic Activation ◽  
Cooperative Catalysis ◽  
New Strategy ◽  
Yin And Yang ◽  
Dual Catalysis ◽  
Chiral Esters ◽  
High Stereoselectivity ◽  
Operational Simplicity

<p>Carbonyl and amine are yin and yang in organocatalysis that mutually activate and transform each other. As intrinsically reacting partners, carbonyl and amine tend to condensate, depleting their individual activity when employed as catalysts. Though widely established as prominent catalytic strategies, aminocatalysis and carbonyl catalysis seems not coexist well and a cooperative amine/carbonyl dual catalysis remains virtually unknown. Here we report a cooperative primary amine and ketone dual catalysis in the asymmetric <i>α</i>-hydroxylation with H<sub>2</sub>O<sub>2</sub>. Besides participating in the typical enamine catalytic cycle, the chiral primary amine catalyst was found to work cooperatively with a ketone catalyst to activate H<sub>2</sub>O<sub>2</sub> <i>via</i> an oxaziridine intermediate derived from<i> in-situ</i> generated ketimine intermediate. The resulted enamine-oxaziridine coupling then facilitated highly-controlled hydroxylation of <i>β</i>-ketocarbonyls that are not possible with other catalytic methods. The dual catalytic approach allows for highly enantioselective <i>α</i>-hydroxylation of a broad range of <i>β</i>-ketocarbonyls. Particularly, late-stage hydroxylation for peptidyl amide or chiral esters can also be achieved with high stereoselectivity. With its operational simplicity and mild conditions, this cooperative amine/ketone catalysis provides a new strategy in catalytic activation of H<sub>2</sub>O<sub>2</sub> and expands the domain of typical amine and carbonyl catalysis to include those challenging transformations.</p>

The Cinchona Primary Amine-Catalyzed Asymmetric Epoxidation and Hydroperoxidation of α,β-Unsaturated Carbonyl Compounds with Hydrogen Peroxide

2013 ◽  
Vol 135 (17) ◽  
pp. 6677-6693 ◽  
Author(s):  
Olga Lifchits ◽  
Manuel Mahlau ◽  
Corinna M. Reisinger ◽  
Anna Lee ◽  
Christophe Farès ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Primary Amine ◽  
Carbonyl Compounds ◽  
Asymmetric Epoxidation

ChemInform Abstract: The Cinchona Primary Amine-Catalyzed Asymmetric Epoxidation and Hydroperoxidation of α,β-Unsaturated Carbonyl Compounds with Hydrogen Peroxide.

ChemInform ◽  
2013 ◽  
Vol 44 (42) ◽  
pp. no-no
Author(s):  
Olga Lifchits ◽  
Manuel Mahlau ◽  
Corinna M. Reisinger ◽  
Anna Lee ◽  
Christophe Fares ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Primary Amine ◽  
Carbonyl Compounds ◽  
Asymmetric Epoxidation

Peroxidase Localization in Hartmanella Trophozoites

1971 ◽  
Vol 29 ◽  
pp. 346-347 ◽  
Author(s):  
George E. Childs ◽  
Joseph H. Miller
Keyword(s):  
Hydrogen Peroxide ◽  
Ultrastructural Localization ◽  
Pathogenic Strain ◽  
Oxidative Enzymes ◽  
Differential Centrifugation ◽  
Electron Microscopic ◽  
Microscopic Studies ◽  
The Subject ◽  
Axenic Cultures

Biochemical and differential centrifugation studies have demonstrated that the oxidative enzymes of Acanthamoeba sp. are localized in mitochondria and peroxisomes (microbodies). Although hartmanellid amoebae have been the subject of several electron microscopic studies, peroxisomes have not been described from these organisms or other protozoa. Cytochemical tests employing diaminobenzidine-tetra HCl (DAB) and hydrogen peroxide were used for the ultrastructural localization of peroxidases of trophozoites of Hartmanella sp. (A-l, Culbertson), a pathogenic strain grown in axenic cultures of trypticase soy broth.

Fluorescent proteins for in vivo imaging, where's the biliverdin?

2020 ◽  
Vol 48 (6) ◽  
pp. 2657-2667
Author(s):  
Felipe Montecinos-Franjola ◽  
John Y. Lin ◽  
Erik A. Rodriguez
Keyword(s):  
Hydrogen Peroxide ◽  
In Vivo Imaging ◽  
Near Infrared ◽  
Fluorescent Protein ◽  
Fluorescent Proteins ◽  
Fluorescent Imaging ◽  
Infrared Light ◽  
Red Fluorescent Protein ◽  
Color Palette

Noninvasive fluorescent imaging requires far-red and near-infrared fluorescent proteins for deeper imaging. Near-infrared light penetrates biological tissue with blood vessels due to low absorbance, scattering, and reflection of light and has a greater signal-to-noise due to less autofluorescence. Far-red and near-infrared fluorescent proteins absorb light &gt;600 nm to expand the color palette for imaging multiple biosensors and noninvasive in vivo imaging. The ideal fluorescent proteins are bright, photobleach minimally, express well in the desired cells, do not oligomerize, and generate or incorporate exogenous fluorophores efficiently. Coral-derived red fluorescent proteins require oxygen for fluorophore formation and release two hydrogen peroxide molecules. New fluorescent proteins based on phytochrome and phycobiliproteins use biliverdin IXα as fluorophores, do not require oxygen for maturation to image anaerobic organisms and tumor core, and do not generate hydrogen peroxide. The small Ultra-Red Fluorescent Protein (smURFP) was evolved from a cyanobacterial phycobiliprotein to covalently attach biliverdin as an exogenous fluorophore. The small Ultra-Red Fluorescent Protein is biophysically as bright as the enhanced green fluorescent protein, is exceptionally photostable, used for biosensor development, and visible in living mice. Novel applications of smURFP include in vitro protein diagnostics with attomolar (10−18 M) sensitivity, encapsulation in viral particles, and fluorescent protein nanoparticles. However, the availability of biliverdin limits the fluorescence of biliverdin-attaching fluorescent proteins; hence, extra biliverdin is needed to enhance brightness. New methods for improved biliverdin bioavailability are necessary to develop improved bright far-red and near-infrared fluorescent proteins for noninvasive imaging in vivo.

Protective effect of chitooligosaccharides on hydrogen peroxide-induced PC-12 cells death by inhibition of oxidative damage

2010 ◽  
Vol 34 (8) ◽  
pp. S27-S27
Author(s):  
Xueling Dai ◽  
Ping Chang ◽  
Ke Xu ◽  
Changjun Lin ◽  
Hanchang Huang ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Oxidative Damage ◽  
Protective Effect ◽  
Pc 12 Cells ◽  
Cells Death

Signal-regulated oxidation of proteins via MICAL

2020 ◽  
Vol 48 (2) ◽  
pp. 613-620
Author(s):  
Clara Ortegón Salas ◽  
Katharina Schneider ◽  
Christopher Horst Lillig ◽  
Manuela Gellert
Keyword(s):  
Signal Transduction ◽  
Hydrogen Peroxide ◽  
Cell Death ◽  
Redox Regulation ◽  
Signal Transduction Pathways ◽  
Cellular Functions ◽  
Intracellular Signals ◽  
Amino Acid Side Chains ◽  
Specific Receptors ◽  
Sulfur Containing

Processing of and responding to various signals is an essential cellular function that influences survival, homeostasis, development, and cell death. Extra- or intracellular signals are perceived via specific receptors and transduced in a particular signalling pathway that results in a precise response. Reversible post-translational redox modifications of cysteinyl and methionyl residues have been characterised in countless signal transduction pathways. Due to the low reactivity of most sulfur-containing amino acid side chains with hydrogen peroxide, for instance, and also to ensure specificity, redox signalling requires catalysis, just like phosphorylation signalling requires kinases and phosphatases. While reducing enzymes of both cysteinyl- and methionyl-derivates have been characterised in great detail before, the discovery and characterisation of MICAL proteins evinced the first examples of specific oxidases in signal transduction. This article provides an overview of the functions of MICAL proteins in the redox regulation of cellular functions.

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