Search results for "Reducing agent"
showing 10 items of 51 documents
Indirect oxidation of amino acid phenylhydrazides by mushroom tyrosinase.
2006
We have investigated oxidation of amino acid phenylhydrazides by mushroom tyrosinase in the presence of 4-tert-butylcatechol and N-acetyl-l-tyrosine. Spectrophotometric measurements showed gradual disappearance of 4-tert-butyl-o-benzoquinone, generated by oxidation of 4-tert-butylcatechol with sodium periodate, after addition of amino acid phenylhydrazides. However, the presence of the phenylhydrazides did not influence the concentration of 4-tert-butyl-o-benzoquinone formed during enzymatic oxidation. Oxygen consumption measurements demonstrated that in a mixture both compounds were oxidized but the reaction rate was proportional to the concentration of the catechol. In the oxidation of N-…
Efficient DNA Cleavage Induced by Copper(II) Complexes of Hydrolysis Derivatives of 2,4,6‐Tri(2‐pyridyl)‐1,3,5‐triazine in the Presence of Reducing A…
2007
The reaction of 2,4,6-tri(pyridyl)-1,3,5-triazine (ptz) and copper(II) salts in dmf/water (1:1) results in the hydrolysis of ptz and formation of the anions bis(2-pyridylcarbonyl)amide (ptO2–) and bis(2-pyridylamine)amide (ptN2–), which are found in the complexes [Cu(ptN2)(OAc)]·3H2O (1), [Cu(ptO2)(OAc)(H2O)]·H2O (2), [Cu(ptN2)(for)]·3H2O (3) (for = formate), [Cu(ptO2)(for)(H2O)] (4), [Cu(ptO2)(benz)]·H2O (5) (benz = benzoate), and [Cu(ptO2)F(H2O)]2·3H2O (6). This report includes the chemical and spectroscopic characterization of all these complexes along with the crystal structures of 4–6. The coordination spheres of CuII in 4 and 5 are best described as distorted tetragonal square pyramid…
Bioprospective of Sorbus aucuparia leaf extract in development of silver and gold nanocolloids
2010
At the present time the bioprospective field is a dynamic area of research. The rapid biosynthesis of silver and gold nanoparticles without using toxic chemicals is reported here. Sorbus aucuparia is omnipresent in Europe. The aqueous leaves extract of the plant were used as reducing agent for the synthesis of silver and gold nanoparticles from their salt solutions. The synthesized nanoparticles were spherical, triangular and hexagonal in shape with an average size of 16 and 18nm for silver and gold, respectively. Different extract quantities, metal concentrations, temperatures and contact times were investigated to find their effect on nanoparticles synthesis. The resulting silver and gold…
A new procedure for the Antioxidant capacity dpph assessment in small samples.
2018
The antioxidant capacity of a substance is its ability to prevent or slow down oxidation. This reaction is a transfer of electrons. The molecule catching electrons is the oxidative agent and the molecule giving electrons is the reducing agent. Oxidative stress is toxic for the cells, and it can be limited by different pathways: the inhibition of enzymes responsible of the production of oxidative species, the synthesis, activation or stabilization of antioxidant enzymes, and finally by direct scavenging of radical species. In living organisms, especially in association to the respiration process, free radicals are commonly produced. Antioxidant are naturally present to prevent damages, and t…
Aminomethyl-Substituted Ferrocenes and Derivatives: Straightforward Synthetic Routes, Structural Characterization, and Electrochemical Analysis
2013
A variety of aminomethyl-substituted ferrocenes and the parent compounds (iminomethyl)ferrocenes, azaferrocenophanes, and diferrocenylamines can be selectively synthesized from reductive amination of 1,1′-diformylferrocene or formylferrocene. The optimized one- or two-step reactions have delivered 13 new compounds, isolated in 65–97% yields, which include tertiary (ferrocenylmethyl)amines and azaferrocenophanes by using NaBH(OAc)3 as a mild reducing agent and (iminomethyl)ferrocenes and secondary (ferrocenylmethyl)amines by using LiAlH4. X-ray structures of representative members of these ferrocene derivative families have evidenced the preferred conformation adopted by ferrocene backbones,…
A redox-sensitive nanofluidic diode based on nicotinamide-modified asymmetric nanopores
2017
[EN] We demonstrate a redox-sensitive nanofluidic diode whose ion rectification is modulated by the oxidation and reduction of chemical moieties incorporated on its surface. To achieve this goal, we have first synthesized the chemical compounds 1-(4-aminobutyl)-3-carbamoylpyridin-1-ium (Nic-BuNH2) and 3-carbamoyl-1-(2,4-dinitrophenyl)pyridinium (Nic-DNP). Then, the surface of track-etched single asymmetric nanopores is decorated with the redox-sensitive Nic-BuNH2 and Nic-DNP molecules using carbodiimide coupling chemistry and Zincke reaction, respectively. The success of the modification reactions is monitored through the changes in the current¿voltage (I¿V) curves prior to and after pore f…
First Highly Diastereoselective Synthesis of syn α-Methyl β-Fluoroalkyl β-Amino Esters
1999
A new two-step approach for the diastereoselective synthesis of the syn α-methyl β-fluoroalkyl β-amino esters 4 has been developed. This approach is based on the chemical reduction of the fluorinated β-enamino esters 3, which have been previously obtained from imidoyl chlorides 1 and lithium ester enolates, with ZnI2/NaBH4 as the reducing agent. The process takes place with high syn diastereoselectivity and good to excellent yields. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction.
Oxygen Availability, Energy Metabolism, and Metabolic Rate in Invertebrates and Vertebrates
1988
It has often been emphasized that primitive life originated in an environment devoid of oxygen. The first eukaryotic cells, however, appeared some 1.4 billion years ago when the earth’s atmosphere had already turned from a mildly reducing to an oxidizing one by the photosynthetic action of prokaryotes that used H20 as reducing agent (see Harold 1986, for review). The presence of free oxygen obviously was a major force shaping the evolution of eukaryotic cells. As a consequence all animals are primarily aerobes, using respiratory chains with oxygen as electron acceptor (oxidant) and membrane-bound ATP synthases for the production of ATP.
ChemInform Abstract: New Strategy for the Stereoselective Synthesis of Fluorinated β-Amino Acids.
2010
Racemic and chiral nonracemic α-substituted and α-unsubstituted β-fluoroalkyl β-amino acid derivatives 6 and 9 have been synthesized in two steps starting from fluorinated imidoyl chlorides 1 and ester enolates. This approach is based on the chemical reduction of previously obtained γ-fluorinated β-enamino esters 4 by using ZnI2/NaBH4 in a nonchelated aprotic medium (dry CH2Cl2) as the reducing agent. A metal-chelated six-membered model has been suggested to explain the stereochemical outcome of the reduction reaction. The process takes place with high yields and with moderate to good diastereoselectivity. The best results related to diastereoselective reduction of chiral β-enamino esters 4…
Hyperbranched polyethylenimine-supported copper(II) ions as a macroliganted homogenous catalyst for strict click reactions of azides and alkynes in w…
2019
Abstract Loading hyperbranched polyethylenimine (PEI) with copper(II) ions leads to the formation of a new water-soluble metallodendritic polymer Cu(II)-PEI that has been found to effectively catalyze the clickable azide-alkyne [3 + 2] cycloaddition reactions in water under ambient conditions, in the lack of any external reducing agent. A positive dendritic effect on the catalyst activity was observed in the click of 1,2,3-triazole by lowering the reduction potential of copper(II) into the in-situ generation of the catalytically active species copper(I). The reaction proceeds straightforwardly to afford the corresponding 1,4-disubstituted-1,2,3-triazole derivatives in a regioselective manne…