- LOW-ODOR THIOGLYCOLIC ACID COMPOSITION
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The invention relates to a low-odor thioglycolic acid composition comprising a linear or cyclic organic acid comprising from 1 to 3 carboxylic acid functions and a saturated or unsaturated, linear or branched or cyclic hydrocarbon chain containing from 1 to 10 carbon atoms; and also to the process for preparing the composition and to its uses.
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- A new procedure for thioester deprotection using thioglycolic acid in both homogeneous and heterogeneous phase
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Classic acetyl thioester protection/deprotection methodologies are widely used in organic synthesis, but deprotection step usually requires harsh conditions not suitable for labile substrates. In this work, a new method for thioester deprotection using a thiotransesterification approach is described. Firstly, thioglycolic acid (TGA) was identified as a good deprotecting reagent in solution. In order to develop a thiol polymer-supported reagent, TGA was anchored to a PEG-based resin through an amide bond (TG-NCO-SH). Both homogeneous and heterogeneous approaches were conveniently carried out at room temperature, in aqueous buffer at pH 8. The mild conditions were suitable for alkyl and phenyl thioesters. Moreover labile thioesters containing thiazolidine and oxazolidine scaffolds, bearing amine, ester and acetal functionalities were also deprotected. The polymer-supported TGA gave better deprotection yields compared to TGA in solution, yields ranging from 61 to 90%. The feasibility of the recovery and reuse of TG-NCO-SH reagent was explored, showing it can be reused at least five times without lossing the activity.
- Mahler, Graciela,Saiz, Cecilia,Villamil, Valentina
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- A mercapto-acetic acid (by machine translation)
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The invention discloses mercapto acetic acid, comprises the following steps: 1) in the reactor, adding benzenedimethanol acetic acid, a chloroethyl acid sodium, carbon disulfide, stirring, drop alkalizing solution, reaction finishes, separate oil phase and aqueous phase; 2) after the branching off of the oil phase mixture, recovering unreacted carbon disulfide, recycled, residual mixture acid into weak acid solution, adding an organic solvent extraction 2 - 3 time, combined with the organic phase, the aqueous solution of the salt, water washing, separate oil phase and aqueous phase; 3) divide the oil phase of the distillation process, recycling the organic solvent, the residue is mercapto acetic acid. In order to carbon disulfide with alkali reaction generating mercapto, with the chloropropyl sodium acetate reaction to produce sodium thioglycolate, adding the proper amount of acid, organic solvent, alkaline solution, low material cost, less reagent consumption; excess of carbon disulfide, reused after being recycled, the utilization rate is high, a clean production process; mild reaction conditions, the reaction time is short, does not need high temperature and high pressure, the equipment investment cost is low. (by machine translation)
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Paragraph 0030; 0031
(2017/05/26)
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- Synthesis of an enantiopure thioester as key substrate for screening the sensitivity of penicillin binding proteins to inhibitors
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The synthesis of the enantiopure thioester (R)-2-(2-benzamidopropanoylthio)acetic acid was developed. After the exploration of several activation methods, reaction conditions were found for the formation of the thioester bond in the presence of propylphosphonic anhydride with high enantioselectivity (ee > 99%). The thioester activity of Penicillin Binding Proteins is helpful in research programs looking for new lead structures to overcome the problem of bacterial resistance.
- Simon, Justine F.,Bouillez, André,Frère, Jean-Marie,Luxen, André,Zervosen, Astrid
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- Discovery of 2-pyridineformamide thiosemicarbazones as potent antiausterity agents
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Series of 2-pyridineformamide thiosemicarbazones were synthesized. Their preferential cytotoxicity in nutrient deprived medium (NDM) was evaluated using PANC-1 human pancreatic cancer cells by employing an antiausterity strategy. 2-Pyridineformamide thios
- Shakya, Bhushan,Yadav, Paras Nath,Ueda, Jun-Ya,Awale, Suresh
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supporting information
p. 458 - 461
(2014/01/23)
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- POLYPEPTIDES HAVING AFFINITY FOR HER2
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HER2 binding polypeptides comprising the amino acid sequence EX1 RNAYWEIA LLPNLTNQQK RAFIRKLYDD PSQSSELLX2E AKKLNDSQ wherein X1 in position 2 is M, I or L, and X2 in position 39 is S or C (SEQ ID NO:1) are disclosed. Moreover, such peptides comprising a chelating environment are disclosed. Also radiolabeled polypeptides formed by the peptides comprising a chelating environment and radionuclides are disclosed. Furthermore, methods of in vivo imaging of the body of a mammalian subject having or suspected of having a cancer characterized by overexpression of HER2 comprising administration of such a radiolabeled polypeptide followed by obtainment of an image of the body using a medical imaging instrument and also methods of treating such cancer are disclosed. Furthermore, the use of such a radiolabeled polypeptide in diagnosis and treatment of cancer characterized by overexpression of HER2. Nucleic acids encoding the polypeptides, expression vectors comprising the nucleic acids and host cells comprising the expression vectors are also disclosed.
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- Deposition of new thia-containing Schiff-base iron (III) complexes onto carbon nanotube-modified glassy carbon electrodes as a biosensor for electrooxidation and determination of amino acids
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Multiwall carbon nanotubes (MWCNTs) were used as an immobilization matrix to incorporate an Fe (III)-Schiff base complex as an electron-transfer mediator onto a glassy carbon electrode surface. First, the preheated glassy carbon was subjected to abrasive immobilization of MWCNTs by gently rubbing the electrode surface on filter paper supporting the carbon nanotubes. Second, the electrode surface was modified by casting 100 μL of an Fe (III)-complex solution (0.01 M in ACN). The cyclic voltammograms of the modified electrode in an aqueous solution displayed a pair of well-defined, stable and nearly reversible reductive oxidation redox systems with surface confined characteristics. Combinations of unique electronic and electrocatalytic properties of MWCNTs and Fe (III)-Schiff base complexes resulted in a remarkable synergistic augmentation of the response. The electrochemical behavior and stability of the modified electrode in aqueous solutions at pH 1-9 were characterized by cyclic voltammetry. The apparent electron transfer rate constant (Ks) and transfer coefficient (a) were determined by cyclic voltammetry and were approximately 7 s-1 and 0.55, respectively. The modified electrodes showed excellent catalytic activity towards the oxidation of amino acids at an unusually positive potential in acidic solution. They also displayed inherent stability at a wide pH range, fast response time, high sensitivity, low detection limit and had a remarkably positive potential oxidation of amino acids that decreased the effect of interferences in analysis. The linear concentration range, limits of detection (LOD), limits of quantization (LOQ) and relative standard deviation of the proposed sensor for the amino acid detection were 1-55,000, 1.10-13.70, 2.79-27.14 and 1.30-5.11, respectively.
- Saghatforoush, Lotfali,Hasanzadeh, Mohammad,Shadjou, Nasrin,Khalilzadeh, Balal
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experimental part
p. 1051 - 1061
(2011/04/16)
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- New polypeptides having affinity for HER2
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HER2 binding polypeptides comprising the amino acid sequence EX1RNAYWEIA LLPNLTNQQK RAFIRKLYDD PSQSSELLX2E AKKLNDSQ wherein X1 in position 2 is M, I or L, and X2 in position 39 is S or C (SEQ. ID NO. 1) are disclosed. Moreover, such peptides comprising a chelating environment are disclosed. Also radiolabeled polypeptides formed by the peptides comprising a chelating environment and radionuclides are disclosed. Furthermore, methods of in vivo imaging of the body of a mammalian subject having or suspected of having a cancer characterized by overexpression of HER2 comprising administration of such a radiolabeled polypeptide followed by obtainment of an image of the body using a medical imaging instrument and also methods of treating such cancer are disclosed. Furthermore, the use of such a radiolabeled polypeptide in diagnosis and treatment of cancer characterized by overexpression of HER2. Nucleic acids encoding the polypeptides, expression vectors comprising the nucleic acids and host cells comprising the expression vectors are also disclosed.
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- Polypeptide libraries with a predetermined scaffold
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Populations of polypeptide variants based on a common scaffold, each polypeptide in the population comprising the scaffold amino acid sequence EXXXAXXEIX XLPNLTXXQX XAFIXKLXDD PSQSSELLSE AKKLNDSQ or AKYAKEXXXAXX EIXXLPNLTX XQXXAFIXKL XDDPSQSSEL LSEAKKLNDS Q, wherein each X individually corresponds to an amino acid residue which is varied in the population are disclosed. Also populations of polynucleotides, wherein each member encodes a member of a polypeptide population are disclosed. Furthermore, combinations of such polypeptide populations and such polynucleotide populations are disclosed, wherein each member of polypeptide population is physically or spatially associated with the polynucleotide encoding that member via means for genotype-phenotype coupling. Furthermore, methods for selecting a desired polypeptide having an affinity for a predetermined target from a population of polypeptides, isolation of a polynucleotide encoding a desired polypeptide having an affinity for a predetermined target, identifying a desired polypeptide having an affinity for a predetermined target, selecting and identifying a desired polypeptide having affinity for a predetermined target, and production of a desired polypeptide having an affinity for a predetermined target are disclosed.
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- Carbodiimides comprising thiocarbamide acid ester groups
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Thiocarbamides comprising at least one carbodiimide group and at least one thiocarbamic ester group of the formula
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- Improvement of a process for synthesis of thioglycolic acid
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An environmentally clean process was proposed for synthesis of thioglycolic acid by condensation of monochloroacetic acid with sodium disulfide, followed by electrochemical reduction of the resulting mixture.
- Islamgulova,Shitova,Akhmerova,Tomilov
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p. 1438 - 1440
(2007/10/03)
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- S-4-Methoxytrityl mercapto acids: Synthesis and application
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4-Methoxytrityl (Mmt)-mercapto acids were obtained either by the reaction of mercapto acids with Mmt-chloride or by the reaction of halo acids with Mmt-thiol. The derivatives obtained were used in the solid-phase synthesis of small libraries of mercaptoacylamino acids and mercaptoacyl peptides. The removal of the Mmt-group was performed by treatment with trifluoroacetic acid (TFA) in dichloromethane (DCM) using triethylsilane (TES) as scavenger.
- Mourtas, Spyros,Gatos, Dimitrios,Kalaitzi, Vagiani,Katakalou, Christina,Barlos, Kleomenis
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p. 6965 - 6967
(2007/10/03)
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- Designer ligands. Part 2. Synthesis of novel, dithiadicarboxamide ligands
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Novel, sulfur-containing diamide ligands have been synthesised, and preliminary complexation studies indicate their selectivity for palladium (II) over copper (II), nickel (II) and cobalt (II).
- Hagemann, Justin P.,Kaye, Perry T.
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p. 303 - 310
(2007/10/03)
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- Process for synthesizing substituted 2-benzo [b]thiophenecarboxylic acids and salts thereof
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A process for the preparation of a substituted 2-benzo[b]thiophenecarboxylic acid compound or an alkali metal salt thereof, which comprises reacting a halobenzoyl derivative with mercaptoacetic acid in the presence of an alkali metal hydroxide and water. Substituted 2-benzo[b]thiophenecarboxylic acid compounds and alkali metal salts thereof are useful as intermediates for pharmaceuticals, agricultural chemicals, material preservatives, and the like.
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- Molecular rearrangement of sulfur compounds IX : Pyrolysis of 2-phenylimino-3-arylamino-4-thiazolidinone derivatives
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Pyrolysis of 2-phenylimino-3-arylamino-4-thiazolidinone I, II (Ar = Ph, p-tolyl) by heating at ca. 250°C in a sealed tube gives rise to H2S, benzonitrile, acetophenone, arylamines, phenyl isothiocynate, thioglycolic acid, arylhydrazines, N-phenyl-N'-aryl thiourea, benzimidazole, and 3-phenyl-1,2,4-benzotriazines. Analogous results in addition to toluene, bibenzyl, stilbene, bibenzylamine and acetamide were also obtained on pyrolysis of 2-phenylimino-3-benzylamino-4-thiazolidinone (III). In the presence of isoquinoline as a radical trap, (III) gave 1-benzylisoquinoline beside the previous products. A free radical mechanism has been postulated to take place through the homolysis of the N-N and C-S bonds to account for the identified products.
- Gaber,Atalla,El-Dean, A. M. Kamal
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- Metal radionuclide labeled proteins for diagnosis and therapy
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Protein, ligand and anti-ligand conjugated chelated metal radionuclides are provided for use in vivo. Intermediates are provided for preparing the compositions efficiently.
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- Triphendioxazine dyestuffs
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The novel triphendioxazine dyestuffs of the formula STR1 in which the substituents R, R', T1, T2, X, Y and n have the meanings given in the description are highly suitable for the dyeing and printing of cellulose-containing or amido-containing material.
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- Oligomers with polydiene sequences and photocrosslinkable grafts and their application particularly in coating metals
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Oligomers with polydiene sequences and crosslinkable grafts are useful as coatings for protecting metal surfaces as well as inking buffers. The oligomers contain a polydiene sequence of 1-100 diene links, from 1 to 20 polar functional groups, and from 1-20 acrylic or methacrylic groups. The oligomers have the general formula: STR1
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- Metal radionuclide labeled proteins for diagnosis and therapy
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Protein conjugated chelated metal radionuclides are provided for use in vivo. Intermediates are provided for preparing the polypeptide compositions efficiently.
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- MOLECULAR REARRANGEMENTS OF SULPHUR COMPOUNDS (II) PYROLYSIS OF SOME SUBSTITUTED THIAZOLIDINONES
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Thermal rearrangement of 2,3-diarylthiazolidine-4-one (I and II) provided H2S, H2O, benzene and its alkyl derivatives, thioglycolic acid, aromatic primary amine, benzonitrile, biaryl, tetraphenylthiophene, indole derivatives, benzil, acetophenone derivatives and benzthiazole derivatives.A suitable mechanism has been suggested which explains the obtained products.
- Atalla, A. A.,Gaber, A. M.,El-Dean, A. M. Kamal,Mohamed, Th. A.
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p. 255 - 260
(2007/10/02)
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- Method of radiolabeling chelating compounds comprising sulfur atoms with metal radionuclides
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Chelating compounds which comprise one or more sulfur atoms and are to be radiolabeled with metal radionuclides to form the corresponding chelates are disclosed. The chelating compounds comprise thioacetal or hemithioacetal sulfur protecting groups which are displaced during the radiolabeling reaction, which is conducted at acidic pH, such that bonds form between said sulfur atoms and said radionuclide. The resulting metal radionuclide chelates have diagnostic and therapeutic medical uses.
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- Metal radionuclide labeled proteins for diagnosis and therapy
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Protein conjugated chelated metal radionuclides are provided for use in vivo. Intermediates are provided for preparing the polypeptide compositions efficiently.
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- THE REACTION OF DICHLOROACETIC ACID WITH HYDROSULFIDES
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The main product of the reaction of dichloroacetic acid with hydrosulfides is dithioglicolic acid.By-products are sulfur, thioglicolic acid, and polysulfides.---Key words: dichloroacetic acid, hydrosulfides, dithioglycolic acid, gem-dichlorides; reduction.
- Darles, Pascale,Labat, Yves,Vallee, Yannick
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- KINETICS ANALYSIS OF THE DECAY OF PHENYLHYDRAZONOPROPANEDINITRILE ADDITION PRODUCTS WITH THIOLS IN AQUEOUS SOLUTIONS
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The reactions of phenylhydrazonopropanedinitriles with thiols are reversible and with increasing pH-values of aqueous solutions the equilibrium is shifted them to the side of the reactants.A mechanism of decay of corresponding addition products was proposed and the kinetic description based on this mechanism is in a good agreement with the obtained experimental data.From the viewpoint of the decay, the pH-dependent dissociation of the proton of the imino group formed by addition of thiol to the nitrile carbon atom plays a decisive role.The obtained knowledge is useful with respect to the use of phenylhydrazonopropanedinitriles as affinants for selective and reversible sorption of low-molecular thiols and thiol-proteins in affinity chromatography as well as for the study of the mechanism of the effect of these substances in oxidative and photosynthetic phosphorylation and biological systems in general.
- Antalik, Marian,Sturdik, Ernest,Podhradsky, Dusan,Polekova, Ingrid,Drobnica, Ludovit
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p. 3387 - 3396
(2007/10/02)
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- Reduction Potentials and Exchange Reactions of Thiyl Radicals and Disulfide Anion Radicals
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Redox equilibria between RS. and -S-S-- radicals, and between these types of radical and phenoxyl and chlorpromazine (ClPz.2+) radicals, have been investigated in aqueous solutions at pHs over the range 6-10 to obtain a self-consistent set of redox potentials for the reactions PhO. + H+ + e- = PhOH (4), RSS.R + 2H+ + e- = 2RSH (11), and RS. + H+ + e- = RSH (18), in sulfur systems with alkyl R groups.Absolute standard potentials were calculated on the of E0 = 0.83 V for the chlorpromazine couple.The results for E04 (=1.35 +/- 0.02 V) and E018 (=1.33 +/- 0.02 V) were in agreement with values calculated from thermodynamic data within the known uncertainties.E018 was found to exhibit a falloff when electron-rich groups, such as the two methyls of penicillamine or the CO2- of β-mercaptoacetic acid, were present on the carbon adjacent to the S atom.However, the effect was relatively small (ca. 10-14 mV).E011 was 1.72 +/- 0.02 V for β-mercaptoethanol.The corresponding potentials for the cyclic anions of dithiothreitol, dithioerythritol, and lipoamide were the same within experimental error, but the uncertainties were larger (+/- 0.04 V).For the reaction e- + -S-S- = -S-S-- (22), the magnitude of E022 was calculated to be -1.60 V, showing that only strongly reducing species could donate electrons to disulfide.Rate constants for several of the forward and backward reactions in the equilibria were also determined.
- Surdhar, Parminder S.,Armstrong, David A.
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p. 6532 - 6537
(2007/10/02)
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- Process of production of organic dithio-acids
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Process for the preparation of an organic dithio-acid by reaction of the corresponding dithio-ester and an alkali metal or alkaline earth metal hydrosulphide in a solvent in the presence of an excess of H2 S and treatment with a mineral acid. The dithioic acids so obtained can be utilized as collectors for the flotation of minerals.
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- POLAROGRAPHY OF METHYLENE BIS(THIOACETIC ACID) IN AQUEOUS SOLUTIONS AND IN AQUEOUS ORGANIC SOLVENT MIXTURES
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The polarographic behaviour of methylene bis (thioacetic acid) (referred to herein as R-S-CH2-S-R) at the d.m.e. has been studied in aqueous and in 20 per cent v/v methanol, ethanol, acetonitrile, DMF and DMSO media in the presence of 0.1 M KNO3 and 0.001 per cent Triton-X-100.The effects of changes in pH, concentration, mercury pressure and different supporting electrolytes, viz.KNO3, KCl, NaCl, NaClO4 (CH3)4NBr and (C2H5)4NBr on the wave characteristics and the mechanism of the electrode reaction, have been studied.Well defined reversible and diffusion controlled cathodic waves were obtained between pH 11 and 12.80.Evidences obtained show that the cathodic wave of R-S-CH2-S-R at the d.m.e. in aqueous solutions and aqueous organic solvent mixtures is due to the reduction of R-S-CH2-S-R to RSH.The diffusion current is linearly related to the concentration of R-S-CH2-S-R in the 0.33-2 mM concentration range and may thus be used for quantitative determination.
- Saxena, R. S.,Parikh, R. D.,Gupta, K. C.
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p. 213 - 222
(2007/10/02)
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- High- and Low-Potential Flavin Mimics. 2. 3,7,10-Trimethyl-(1H,3H,5H,7H,9H,10H)-pyrimidopteridine-2,4,6,8-tetrone Dianion Reduction of Carbonyl, Nicotinamides, and Alkyl Disulfide Functional Groups
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3,7,10-Trimethyl-(3H,7H,9H,10H)-pyrimidopteridine-2,4,6,8-tetrone (PPTox) and its conjugate base (PPTox-) undergo two-electron reduction to yield 3,7,10-trimethyl-(1H,3H,5H,7H,9H,10H)-pyrimidopteridine-2,4,6,8-tetrone (PPTH2) and its dianion (PPT2-) (Scheme I).The two-electron redox potential E0' is 150 mV more negative than that of the corresponding 3-methyllumiflavin (Flox)/1,5-dihydro-3-methyllumiflavin (FlH2 + FlH-) couple.Reductive alkylation of PPTH2 with acetaldehyde (Scheme II) provides the N5-ethyl derivative of PPTH2 (N5-EtPPTH2) which is an analogue of the well studied 1,5-dihydro-N5-ethyl-3-methyllumiflavin (N5-EtFlH).As in the instance of N5-EtFlH, N5-EtPPTH2 can undergo stepwise oxidation to the thermodynamically stable N5-EtPPT-. radical (analogue of N5-EtFl.) and hence to the two-electron oxidized species N5-EtPPTox (Scheme II).The pKa for the pseidobase formation via reaction of N5-EtPPTox with H2O (7.34) is compared to the similar pKa (4.00) for the reaction of N5-EtFlox+ with H2O.The species PPTox- (like Flox) is not reduced (H2O solvent) with NaCNBH3.However, reduction of a solution of PPTox- containing formaldehyde with NaCNBH3 yields N5-MePPTox and the radical N5-MePPT-. on admittance of O2.The mechanism (Scheme III) involves the initial formation of the N1-carbinolamine of PPTox- which when reduced is subject to reductive alkylation at N5, as in the case of reductive alkylation of PPTH2.The reaction of PPTH2 with formaldehyde has been studied in detail.The reaction resembles, in important details, that for the reaction of FlH2 with formaldehyde.An initial first-order burst in the formation of PPTox- is associated with the competitive reduction of formaldehyde by PPT2- and the formation of the N5-imine of PPT2- (eq 5; Scheme IV).The latter does not apparently revert readily to carbinolamine, due to its electronic stabilization (structures A, B, C, and D).The N5-imine of PPT2- is trapped in further reactions to produce compounds with more positive potentials than that for the PPTox-/PPTH2 couple (possible structures as E, F, etc.).The increase in the rate constant of specific acid catalyzed reduction of formaldehyde by PPT2- (k = 3.3x106 M-2 s-1) over the like constant with FlH- (k = 2.3x104 M-2 s-1) is related to the difference in the two-electron reduction potential for the two (148 mV) by the free energy relationship 67 mV/Δ log k.The predicted free energy relationship for a series of 1,5-dihydroflavins of varying potentials carrying out reduction of a substrate by two-electron transfer would be 60 mV/Δ log k.Thus, toward formaldehyde, PPT2- exhibits the reactivity of a low-potential FlH- molecule.The reaction of PPTH2T (=PPTH2 + PPT- + PPT2-) with m-hydroxybenzaldehyde was studied at pH 5.00 only.In preparative experiments, it was shown that m-hydroxybenzaldehyde was reduced to m-cresol and a trace of m-hydroxybenzyl ...
- Skibo, Edward B.,Bruice, Thomas C.
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p. 3316 - 3328
(2007/10/02)
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- A Novel Method for the Preparation of Thioformates and Thiols by using Thioformimidates
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Several new S-alkylated thioformimidates were synthesized and their applications to the synthesis of thiolformates and thiols were investigated.Keywords - thioformimidates; thiols; thiolformates; thioformanilide; Michel-type addition
- Matsubara, Yoshio,Nakamura, Toshiyuki,Yoshihara, Masakuni,Maeshima, Toshihishi
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p. 3389 - 3391
(2007/10/02)
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- Antimony mercaptides as processing stabilizers for vinyl halide resins
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Novel compositions and use therefore as stabilizers during the production of vinyl halide resins are disclosed which comprise antimony mercaptides having the general formula: STR1 wherein K is 1 to 4; L is 0 to 1; M is 1 to 4; N is 1 to 4; X is oxygen or sulfur; and R is an alkyl, alkenyl, alkynyl having 1 to 18 carbon atoms and combinations thereof. Such compositions when used during vinyl halide resin processing retard discoloration and mechanical degradation at least as effectively as previously known antimony mercaptides while being more economical to produce.
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- SOLVOLYSIS KINETICS AND MECHANISM OF 3-METHYL-1,3-THIAZOLIDINE-2,4-DIONE
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The hydrolysis kinetics of 3-methyl-1,3-thiazolidine-2,4-dione have been studied in aqueous buffers and dilute NaOH solutions.The reaction proceeds via two base-catalyzed steps having different rates.In sodium methoxide solutions 3-methyl-1,3-thiazolidine-2,4-dione undergoes one-step methanolysis giving methyl thioglycolate anion as the final product.The rate-limiting step consists in decomposition of the anion CH3NCOSCH2COOCH3.
- Machacek, Vladimir,Sterba, Vojeslav,Zahradnickova, Helena
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p. 3097 - 3103
(2007/10/02)
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- Rate Constants and Equilibrium Constants for Thiol-Disulphide Interchange Reactions Involving Oxidized Glutathione
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The rate of reduction of oxidized glutathione (GSSG) to glutathione (GSH) by thiolate (RS-) follows a Broensted relation in pKas of the conjugate thiols (RSH): βnuc ca. 0.5.This value is similar to that for reduction of Ellman's reagent: βnuc ca. 0.4 - 0.5.Analysis of a number of rate and equilibrium data, taken both from this work and from the literature, indicates that rate constants, k, for a range of thiolate-disulphide interchange reactions are correlated well by equations of the form log k = C + βnucpKanuc + βcpKac + βlgpKalg ( nuc = nucleophile, c = central, and lg = leaving group sulfur): eq 36 - 38 give representative values of the Broensted coefficients.The values of these Bronsted coefficients are not sharply defined by the available experimental data, although eq 36 - 38 provide useful kinetic models for rates of thiolate-disulfide interchange reactions.The uncertainty in these parameters is such that their detailed mechanistic interpretation is not worthwhile, but their qualitative interpretation - that all three sulphur atoms experience a significant effective negative charge in the transition state, but that the charge is concentrated on the terminal sulfurs - is justified.Equilibrium constants for reduction of GSSG using α,ω-dithiols have been measured.The reducing potential of the dithiol is strongly influenced by the size of the cyclic disulfide formed on its oxidation: the most strongly reducing dithiols are those which can form six-membered cyclic disulfides.Separate equilibrium constants for thiolate anion-disulphide interchange (KS-) and for thiol-disufide interchange (KSH) have been estimated from literature data: KS- is roughly proportional to 2ΔpKa is the difference between the pKas of the two thiols involved in the interchange.The contributions of thiol pKa values to the observed equilibrium constants for reduction of GSSG with α,ω-dithiols appear to be much smaller than those ascribable to the influence of structure on intramolecular ring formation.These equilibrium and rate constants are helpful in choosing dithiols for use as antioxidants in solutions containing proteines: dithiothreitol (DTT), 1,3-dimercapto-2-propanol (DMP), and 2-mercaptoethanol have especially useful properties.
- Szajewski, Richard P.,Whitesides, George M.
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p. 2011 - 2026
(2007/10/02)
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- Process for preparing thiodiglycolic acid
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A process for preparing thiodiglycolic acid comprises contacting bromoacetic acid, diglycolic acid or glycolic acid and hydrogen sulfide in the presence of aqueous hydrogen bromide.
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- Complexes of macrocyclic compounds
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Novel macrocyclic (monocyclic and bicyclic) compounds having nitrogen bridgehead atoms and having in the hydrocarbon bridging chains at least two additional hetero atoms selected from the group consisting of sulfur, oxygen, and nitrogen, when admixed with a compatible cation-donor compound form stable cation-containing macrocyclic complexes which, in turn, can be conveniently dissociated by addition of acid or a quaternizing agent. The novel macrocyclics are valuable for use in the same way and for the same purposes as chelating agents.
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- Azole derivatives
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Azole derivatives of the formula SPC1 Wherein R1 is free or esterified carboxyl or other functionally modified carboxyl group, R2 and R3 each are aryl; A is Cn H2n in which n is an integer from 1 to 10, inclusive; and Z is O or S; and the physiologically acceptable salts thereof, possess, with good compatibility, excellent antiphlogistic activity and, in particular, influence favorably the chronic progressive diseases of the joints, e.g., arthritis. They can be prepared from compounds of the formula SPC2 Wherein X1 is a group convertible into the group --S--A--R1, and R2 and R3 have the values given above.
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- Monocyclic macrocyclic compounds and complexes thereof
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Novel monocyclic macrocyclic compounds having nitrogen bridgehead atoms and having in the hydrocarbon bridging chains at least two additional hetero atoms selected from the group consisting of sulfur, oxygen, and nitrogen, when admixed with a compatible cation-donor compound form stable cation-containing macrocyclic complexes which, in turn, can be conveniently dissociated by addition of acid or a quaternizing agent. The novel macrocyclics are valuable for use in the same way and for the same purposes as chelating agents.
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