Stereochemistry of Dehydrogenation by D-Galactose Oxidase

1971 ◽  
Vol 49 (21) ◽  
pp. 3429-3437 ◽  
Author(s):  
A. Maradufu ◽  
G. M. Cree ◽  
A. S. Perlin
Keyword(s):  
Hydrogen Atom ◽  
Isotope Effect ◽  
Galactose Oxidase ◽  
Relative Impact ◽  
Chemical Transformations ◽  
Product Analysis ◽  
Deuterium Isotope Effect ◽  
Oxidation Rates ◽  
Selective Chemical ◽  
Sugar Derivatives

The stereochemistry of dehydrogenation of the primary carbinol group of D-galactose by D-galactose oxidase has been determined. Using D-galactose-6-d and methyl β-D-galactopyranoside-6-d, it has been established that the reaction involves removal of the pro-S 6-hydrogen atom. This conclusion is based on product analysis, and on the relative impact of the deuterium isotope effect on oxidation rates of substrates having different R:S deuteration patterns. The absolute configurations at C-6 of these substrates have been determined by selective chemical transformations to products of known configuration. The rotational conformation of the 6-carbinol group of D-galactose and its possible relationship to the specificity of the enzyme are discussed, as well as the stereochemistry of reductive deuteration of aldehydo sugar derivatives.

ISOTOPE EFFECTS IN NEUTRAL H2O–D2O IRRADIATED SOLUTIONS AND THE NATURE OF THE REDUCING RADICAL

1962 ◽  
Vol 40 (10) ◽  
pp. 1903-1908 ◽  
Author(s):  
Chava Lifshitz
Keyword(s):  
Hydrogen Atom ◽  
Water Molecule ◽  
Isotope Effect ◽  
Isotope Effects ◽  
Sodium Formate ◽  
Alternative Possibilities ◽  
X Rays ◽  
Deuterium Isotope Effect ◽  
Deuterium Concentration ◽  
Single Water Molecule

Neutral solutions of sodium formate in H2O–D2O mixtures were irradiated by 200-kv X rays. The atomic deuterium isotope effect (αA) and its dependence on deuterium concentration were determined. In a 1 × 10−1 M HCOONa, 96% D2O solution, G(hydrogen) = 1.14 and αA = 4.3. It is concluded that the hydrogen atom cannot be formed from a single water molecule. Possible mechanisms of hydrogen atom formation are discussed. The alternative possibilities for the atoms to react as H or H2O− are viewed in the light of the proposed mechanisms.

THE KINETICS OF THE INHIBITED AUTOXIDATION OF TETRALIN

1964 ◽  
Vol 42 (10) ◽  
pp. 2324-2333 ◽  
Author(s):  
J. A. Howard ◽  
K. U. Ingold
Keyword(s):  
Isotope Effect ◽  
Chain Transfer ◽  
Square Root ◽  
Deuterium Isotope Effect ◽  
First Order ◽  
Oxidation Rates ◽  
First Order Kinetics ◽  
A Value ◽  
Root Relation ◽  
Kinetics Of

The kinetics of the inhibition of the autoxidation of tetralin by 2,6-di-t-butyl-4-methylphenol, phenol, and 4-methoxyphenol have been investigated at 65 °C. The highly hindered 2,6-di-t-butyl-4-methylphenol follows simple first order kinetics and exhibits a normal deuterium isotope effect (kH/kD = 10). The kinetics with phenol are complicated by the fact that the phenoxy radical can abstract a hydrogen atom from both tetralin and its hydroperoxide. This leads to oxidation rates which are inversely proportional to the square root of the phenol concentration. The deuterium isotope effect has about the value to be expected in view of this square root relation. The kinetics with 4-methoxyphenol result from chain transfer and from chain termination by the coupling of 4-methoxyphenoxy radicals. The isotope effect varies between zero and a value that approaches the upper limit of about 10 at low inhibitor concentrations.

scholarly journals Enamine/Transition Metal Combined Catalysis: Catalytic Transformations Involving Organometallic Electrophilic Intermediates

2019 ◽  
Vol 377 (6) ◽  
Author(s):  
Samson Afewerki ◽  
Armando Córdova
Keyword(s):  
Transition Metal ◽  
Metal Complex ◽  
Carbonyl Compounds ◽  
Transition Metal Catalysis ◽  
Chemical Transformations ◽  
Considerable Effort ◽  
Metal Catalysis ◽  
First Report ◽  
Wide Range ◽  
Selective Chemical

AbstractThe concept of merging enamine activation catalysis with transition metal catalysis is an important strategy, which allows for selective chemical transformations not accessible without this combination. The amine catalyst activates the carbonyl compounds through the formation of a reactive nucleophilic enamine intermediate and, in parallel, the transition metal activates a wide range of functionalities such as allylic substrates through the formation of reactive electrophilic π-allyl-metal complex. Since the first report of this strategy in 2006, considerable effort has been devoted to the successful advancement of this technology. In this chapter, these findings are highlighted and discussed.

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