EFFICIENT AND SELECTIVE OXIDATION OF THIOLS TO DISULFIDES BY 1,4-DIAZABICYCLO[2.2.2]OCTANE-DI-N-OXIDE-DI-PERHYDRATE UNDER NEUTRAL AND HETEROGENEOUS CONDITIONS

1,4-Diazabicyclo[2.2.2]octane-di-N-oxide-di-perhydrate[3pc] selectively oxidizes thiols to disulfides in acetonitrile in good yields. The method is generally useful for a wide variety of thiols.     

2-C-branched glycosides from 2'-carbonylalkyl 2-O-Ms(Ts)-C-glycosides. A tandem SN2-SN2 reaction via 1,2-cyclopropanated sugars

[reaction: see text] Under basic conditions, 2'-aldehydo (acetonyl) 2-O-Ms(Ts)-alpha-C-glycosides undergo an intramolecular S(N)2 reaction to form 1,2-cyclopropanated sugars, which react with nucleophiles (alcohols, thiols, and azide) at the anomeric carbon to give 2-C-branched glycosides. By way of contrast, the 1,2-cyclopropanes derived from 2'-ketones only react with thiols to give 2-C-branched thioglycosides.     

CHEMOSELECTIVE ACETYLATION OF ALCOHOLS,AMINES, AND THIOLS WITHOUT CATALYST AND SOLVENT

Microwave induced rapid and selective acetylation of alcohols, amines and thiols with acetic anhydride was carried out under non-catalytic and solvent free conditions.     

2+2] photocycloadditions of thiomaleimides

Thiomaleimides, generated by the addition of bromomaleimides to thiols including cysteine, undergo highly efficient [2+2] photocycloadditions.     

Perfluoroalkylation of 2-Thiopyrimidine Derivatives

The method of perfluoroalkylation of heterocyclic thiols and disulfides by thermolytic reaction with xenon(II) bisperfluoroalkylcarboxylates has been extended to sulfur-containing pyrimidines, including 2-mercaptopyrimidines, symmetrical disulfides, and S-trifluoroacetyl derivatives obtained from the corresponding thiols. The main reaction products are 2-SC_nF_2n+1 (n = 1, 2)-substituted pyrimidines. Their formation proceeds only via disulfides into which the initial thiols and S-trifluoroacetyl derivatives are converted in the reaction medium. Side reactions occurred in the case of trifluoromethylation linked with the perfluoroalkylation of the pyrimidine nucleus at the free 5 position (in the case of the 4,6-dimethyl derivative), or at position 4 or 4 and 5 (for unsubstituted pyrimidine). In addition, the introduction of the CF₃ group at one of the methyl substituents was confirmed by the formation of CH₂CF₃ fragment.     

Cobalt Phthalocyanine‐Based Molecular Materials for the Electrocatalysis and Electroanalysis of 2‐Mercaptoethanol, 2‐Mercaptoethanesulfonic Acid,Reduced Glutathione and L‐Cysteine

We have investigated the electrocatalytic activity of cobalt tetra‐aminophthalocyanine (CoTAPc) for the one‐electron oxidation of thiols of various sizes, namely 2‐mercaptoethanol, 2‐mercaptoethanesulfonic acid, reduced glutathione and L ‐cysteine, using adsorbed monomeric CoTAPc and electropolymerized poly‐CoTAPc films of different thickness on a vitreous carbon electrode. Our results show that the electrocatalytic activity of poly‐CoTAPc films towards the oxidation of the thiols increases slightly with the thickness of the film, but remains similar to that of the adsorbed monomeric CoTAPc. The higher stability of the electropolymerized poly‐CoTAPc films makes them attractive for applications in the activation and/or the detection of thiols. We have assessed this approach by designing ultra‐micro‐carbon‐fiber electrodes, coated with poly‐CoTAPc, and combining their use with different electrochemical techniques (cyclic voltammetry, differential pulse voltammetry and differential normal pulse amperometry) for the electroanalysis of the examined thiols.     

Harnessing the catalytic behaviour of 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP): An expeditious synthesis of thioesters

A novel, efficient, metal-, base- and acid-free straightforward protocol has been developed for the construction of useful thioesters. The immense catalytic potential of HFIP for promoting the thiocarbonylation of acyl halides and thiols is disclosed. HFIP was recovered with ease and reused for further reactions without any loss of reactivity. Both aryl and alkyl thiols bearing electron-donating and electron-withdrawing groups as well as aryl- and alkyl acyl halides worked well in this reaction. Inexpensive precursors, short reaction time, obviating workup, high atom economy, and gram-scale preparation are the significant features of the developed eco-friendly route for S-carbonylation of thiols.     

Synthesis of 2-thio-substituted benzothiazoles via a domino condensation/S-arylation/heterocyclization process

Condensation of carbon disulfide with thiols in the presence of K(2)CO(3) generates carbonotrithioate salts in situ, which undergo coupling with 2-iodoanilines and subsequent intramolecular condensation and elimination under assistance of CuBr to afford 2-thio-substituted benzothiazoles. Both aliphatic and aromatic thiols are compatible with this process, delivering the corresponding heterocycles with good diversity.     

MICROWAVE ACCELERATED TETRAHYDROPYRANYLATION AND DETETRAHYDROPYRANYLATION OF ALCOHOLS,PHENOLS, AND THIOLS CATALYZED BY HYDRATED ZIRCONIA

ABSTRACT

A solvent free and expeditious method for tetrahydropyranylation and detetrahydropyranylation of alcohols, phenols and thiols is described using hydrated zirconia and 3,4-dihydro-2H-pyran (DHP). A comparison of this microwave-accelerated reaction with conventional heating condition is also presented.     

High-performance liquid chromatography-fluorometry for the determination of thiols in biological samples using N-[4-(6-dimethylamino-2-benzofuranyl) phenyl]-maleimide

The selective determination of thiols in biological samples was investigated by high-performance liquid chromatography using N-[4-(6-dimethylamino-2-benzofuranyl)phenyl] maleimide, which was found to give fluorescent products when treated with certain thiols. Six kinds of thiol (reduced glutathione, cysteine, N-acetylcysteine, cysteamine, homocysteine and coenzyme A) could be separated simultaneously within ca. 12 min and determined at final level of sensitivity. The method was successfully applied to the determination of thiols in rat tissues and plasma and in human normal serum.     

Facile reaction of thiols and amines with alkyl 4-hydroxy-2-alkynoates in water under neutral conditions and ultrasound irradiation

This Letter describes an alternative protocol for the Michael addition of thiols to 4-hydroxy-2-alkynoates. The reaction proceeds at room temperature in water under ultrasound irradiation. With amines instead of thiols a sequential conjugate addition/lactonization reaction leads to important 4-amino-furan-2-one derivatives.     

Existence of low-molecular-weight thiols in Caenorhabditis elegans demonstrated by HPLC-fluorescene detection utilizing 7-chloro-N-[2-(dimethylamino)ethyl]-2,1,3-benzoxadiazole-4-sulfonamide

A highly sensitive and simple method using HPLC-fluorescence detection with 7-chloro-N-[2-(dimethylamino)ethyl]-2,1,3-benzoxadiazole-4-sulfonamide (DAABD-Cl) as a fluorogenic reagent demonstrated the existence of the low-molecular-weight thiols in the extract of Caenorhabditis elegans (C. elegans). The method includes derivatization of the thiols with DAABD-Cl at 40 degrees C for 10 min in borate buffer (pH 9.0) containing TCEP, CHAPS and EDTA, separation of the derivatives on an ODS column and fluorometric determination of the derivatives at 510 +/- 15 nm with excitation at 400 +/- 15 nm. The identification of the thiols was made by HPLC-electrospray ionization mass spectrometry (LC-MS) following isolation of the derivatives using HPLC-fluorescence detection. Low-molecular-weight thiols were found to exist in the extract of C. elegans, such as cysteine, cysteinylglycine, gamma-glutamylcysteine, reduced glutathione and two other unidentified thiol compounds, confirming the existence of the 'glutathione cycle' in C. elegans similar to the mammalian body.     

GENERATION AND PARTICIPATION OF O-2 IN 2-NITROPROPANE DIOXYGENASE REACTION

Abstract— 2-Nitropropane dioxygenase (EC 1. 13. 11) of the yeast Hansenula mrakii catalyzes the oxygenative denitrification of 2-nitropropane as follows:

The enzyme is significantly inhibited by superoxide dismutase and various scavengers for superoxide such as cytochrome c , epinephrine, thiols and polyhydric phenols. The scavengers added to the reaction mixture were oxidized or reduced. The addition of superoxide dismutase and the omission of 2-nitropropane or oxygen prevented the oxidation and the reduction of the scavengers. The enzyme catalyzes the formation of nitrite from 2-nitropropane by KO₂ added anaerobically.
One mole of NADH is bound per mole of the enzyme and predominantly the pro-R hydrogen of bound NADH is transferred to superoxide formed enzymatically or provided externally. The enzyme shows incomplete stereospecificity for hydrogen transfer from NADH.     

2-Acyl(aroyl)-1,1,3,3-tetracyanopropenides: II. Synthesis of 2-[2-(alkylsulfanyl)-5-amino-2-aryl-4-cyano-2,3-dihydrofuran-3-ylidenepropanedinitriles by reaction with thiols

Reactions of 2-aroyl-1,1,3,3-tetracyanopropenides with thiols in acid medium led to the formation of the corresponding 2-alkylsulfanyl-substituted 2-(5-amino-2-aryl-4-cyano-2,3-dihydrofuran-3-ylidene)propanedinitriles.     

STUDIES ON THE SYNTHESIS OF THIOLS AND THEIR S-SUBSTITUTED DERIVATIVES

Abstract

Aromatic thiols belong to a group of not yet sufficiently explored compounds. The presence of an active hydrogen atom makes it possible to conduct various chemical conversions and to obtain new S-substituted derivatives.     

In vivo AND PHOTOPHYSICAL STUDIES ON PHOTOOXIDATIVE DAMAGE TO LENS PROTEINS AND THEIR PROTECTION BY RADIOPROTECTORS

Abstract— Photooxidation, whether initiated by an endogenous or exogenous sensitizer, is an important mechanism in light induced damage to the lens. One of the substrates for this damage is lens protein. A porphyrin sensitizer which binds to lens proteins [ mesotetra ( p -sulfonatophenyl) porphyrin (TPPS)] was found to photooxidize Skh-2 pigmented mice lens protein in vivo. Uroporphyrin, a model for a non-binding photosensitizer, did not induce photooxidative damage to the mouse lens.
The radioprotector 3-amino-2-hydroxypropyl phosphorothioate (WR-77913) was investigated as an agent to retard or negate in vivo photooxidative damage to the lens. Intraperitoneal injections of WR-77913 prior to irradiation reduced the TPPS induced photodestruction of lens protein in Skh-2 pigmented mice.
The mechanism of protection was also investigated. Thiols were found to quench both the triplet state of porphyrins and the reactive intermediate singlet oxygen on the order of 10⁵ and 10⁶ M ^-1 s¹ respectively. These are probably not fast enough to explain most of the protection afforded by thiols. An additional mechanism may be the accelerated photobleaching of porphyrins by thiols which protects tissue by reducing the absorptions due to the porphyrins.     

New three-component condensation reaction: synthesis of 1-[(alkylthio)(phenyl)methyl]-naphthalene-2-ol catalyzed by bromodimethylsulfonium bromide (BDMS)

Bromodimethylsulfonium bromide acts as an efficient catalyst for one pot three component condensation reactions of aldehydes, 2-naphthol, and thiols in acetonitrile at room temperature. Various aliphatic and aromatic thiols undergo conjugate addition with in situ generated enone in acetonitrile and provide good yields. The main features of this procedure are mild reaction conditions, good yields, and operational simplicity.     

Comparaison de l''action catalytique de thiols monofonctionnels et de certains thiols bifonctionnels (les mercaptoalcoyl-2 benzimidazoles) sur l''hydrolyse de l''acetate de p-nitrophenyle

Synthesis of bifunctional thiols (2-alkylmercaptobenzimidazoles) and kinetic studies of the catalysis of the hydrolysis of p-nitrophenylacetate by these compounds, and by seven thiols indicates high activity of the 2-mercaptomethylbenzimidazoles in their neutral form, interpreted as the result of nucleophilic catalysis by the thiol function in its neutral state combined with general basic catalysis by the heterocycle.     

KINETICS AND MECHANISM OF COMPLEX FORMATION BETWEEN [PtCl(DIEN)]+ AND THIOLS AND THIOETHERS

Abstract

Reactions of the monofunctional platinum(II) complex, [PtCl(dien)]⁺, with different thiols and thioethers, including biologically important molecules, have been studied as a function of temperature (288.2–308.2K) using conventional electronic spectrophotometry in 0.10 M aqueous hydrochloric acid and by ¹H NMR spectroscopy. The second-order rate constants, k₂, are similar, varying between 1.43 × 10^?3 and 46.1 × 10^?3 M^?1s^?1 at 25°C. The reactivity follows the sequences: D-penicillamine ≤ L-cysteine ≤ glutathione ≤ thiodiglycolic acid ≤ thioglycolic acid ≤ L-methionine ≤ S-methylthioglycolic acid ≤ glycyl-D,L-methionine. However, variation in size, bulkiness and solvation of the entering ligands reflect in their properties as nucleophiles. Large negative values of the entropy of activation (ΔS≠), between ?140 and ?190 J K^?1 mol^?1, indicate that all thiols and thioethers react via the same associative mechanism. Results have been analyzed in relation to the antitumor activity and toxicity of platinum(II) complexes.     

2-Alkylthiopropionaldehyde mercaptals

Conclusions Some 1,2-bis(alkylthio)propenes were obtained by the cleavage of thiols from the mercaptals of a 2-alkylthiopropionaldehyde in the presence of either acids or dialkyl phosphites.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2014–2016, September, 1972.