Mechanism of the Exchange Reaction of Elemental Sulfur with Mercaptobenzothiazole

1956 ◽  
Vol 29 (1) ◽  
pp. 63-66
Author(s):  
G. A. Blokh ◽  
E. A. Golubkova ◽  
G. P. Miklukhin
Keyword(s):  
Experimental Data ◽  
Exchange Reaction ◽  
Elemental Sulfur ◽  
Chemical Properties ◽  
Sulfhydryl Group ◽  
Rapid Exchange ◽  
Technical Properties ◽  
Derivatives Of ◽  
Preceding Study

Abstract As was shown in our preceding study, a rapid exchange of sulfur atoms takes place between elemental sulfur and 2-mercaptobenzothiazole at temperatures corresponding to the conditions of vulcanization of rubber. This indicates the existence of a reaction between the atoms, and also the formation during this reaction of some kind of intermediate compounds. On the basis of the experimental data, it was established that only one of the sulfur atoms of mercaptobenzothiazole enters into the exchange reaction. It was natural to assume, in view of the technical properties of derivatives of mercaptobenzothiazole and its own chemical properties, that the sulfur of the sulfhydryl group takes part in the reaction. In fact, as is shown in another study, 2-mercaptobenzoxazole (I) has a stronger accelerating effect during vulcanization than 2-aminobenzothiazole (II) or 2-oxybenzothiazole (III). Furthermore, it is known that the sulfur in the sulfhydryl group of mercaptobenzothiazole and its derivatives is considerably more mobile than the sulfur in the ring, and is easily converted into other substituents.

scholarly journals The Fluoride Anion-Catalyzed Sulfurization of Thioketones with Elemental Sulfur Leading to Sulfur-Rich Heterocycles: First Sulfurization of Thiochalcones

Molecules ◽  
2021 ◽  
Vol 26 (4) ◽  
pp. 822
Author(s):  
Grzegorz Mlostoń ◽  
Jakub Wręczycki ◽  
Katarzyna Urbaniak ◽  
Dariusz M. Bieliński ◽  
Heinz Heimgartner
Keyword(s):  
Elemental Sulfur ◽  
Fluoride Anion ◽  
Ring Size ◽  
Mild Conditions ◽  
Tetrabutylammonium Fluoride ◽  
Cesium Fluoride ◽  
Secondary Reactions ◽  
Derivatives Of

Fluoride anion was demonstrated as a superior activator of elemental sulfur (S8) to perform sulfurization of thioketones leading to diverse sulfur-rich heterocycles. Due to solubility problems, reactions must be carried out either in THF using tetrabutylammonium fluoride (TBAF) or in DMF using cesium fluoride (CsF), respectively. The reactive sulfurizing reagents are in situ generated, nucleophilic fluoropolysulfide anions FS(8−x)−, which react with the C=S bond according to the carbophilic addition mode. Dithiiranes formed thereby, existing in an equilibrium with the ring-opened form (diradicals/zwitterions) are key-intermediates, which undergo either a step-wise dimerization to afford 1,2,4,5-tetrathianes or an intramolecular insertion, leading in the case of thioxo derivatives of 2,2,4,4-tetramethylcyclobutane-1,3-dione to ring enlarged products. In reactions catalyzed by TBAF, water bounded to fluoride anion via H-bridges and forming thereby its stable hydrates is involved in secondary reactions leading, e.g., in the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone to the formation of some unexpected products such as the ring enlarged dithiolactone and ring-opened dithiocarboxylate. In contrast to thioketones, the fluoride anion catalyzed sulfurization of their α,β-unsaturated analogues, i.e., thiochalcones is slow and inefficient. However, an alternative protocol with triphenylphosphine (PPh3) applied as a catalyst, offers an attractive approach to the synthesis of 3H-1,2-dithioles via 1,5-dipolar electrocyclization of the in situ-generated α,β-unsaturated thiocabonyl S-sulfides. All reactions occur under mild conditions and can be considered as attractive methods for the preparation of sulfur rich heterocycles with diverse ring-size.

The Interactions of adenylates with allosteric citrate synthase

1979 ◽  
Vol 57 (5) ◽  
pp. 385-395 ◽  
Author(s):  
Michael M. Talgoy ◽  
Harry W. Duckworth
Keyword(s):  
Coenzyme A ◽  
Citrate Synthase ◽  
Potent Inhibitor ◽  
Sulfhydryl Group ◽  
Fluorescence Technique ◽  
Allosteric Site ◽  
Acetyl Coenzyme A ◽  
Nitrobenzoic Acid ◽  
Adenylic Acid ◽  
Derivatives Of

Evidence is presented that a number of derivatives of adenylic acid may bind to the allosteric NADH binding site of Escherichia coli citrate synthase. This evidence includes the facts that all the adenylates inhibit NADH binding in a competitive manner and that those which have been tested protect an enzyme sulfhydryl group from reaction with 5,5′-dithiobis-(2-nitrobenzoic acid) in the same way that NADH does. However, whereas NADH is a potent inhibitor of citrate synthase, most of the adenylates are activators. The best activator, ADP-ribose, increases the affinity of the enzyme for the substrate, acetyl-CoA, and saturates the enzyme in a sigmoid manner. A fluorescence technique, involving the displacement of 8-anilino-1-naphthalenesulfonate from its complex with citrate synthase, is used to obtain saturation curves for several nucleotides under nonassay conditions. It is found that acetyl-coenzyme A, coenzyme A, and ADP-ribose all bind to the enzyme cooperatively, and that the binding of each becomes tighter in the presence of KCl the activator, and oxaloacetic acid (OAA), the second substrate. Another inhibitor, α-ketoglutarate, can compete with OAA in the absence of KClbut not in its presence. The nature of the allosteric site of citrate synthase, and the modes of action of several activators and inhibitors, are discussed in the light of this evidence.

Thiol derivatives of cellulose as supports for the immobilization of non-thiol enzymes

1981 ◽  
Vol 46 (7) ◽  
pp. 1693-1700 ◽  
Author(s):  
Peter Gemeiner ◽  
Jiří Zemek
Keyword(s):  
Exchange Reaction ◽  
Proteolytic Activity ◽  
Acetylcholine Esterase ◽  
Mercaptoacetic Acid ◽  
Thiol Groups ◽  
Nucleophilic Reaction ◽  
Disulfide Exchange ◽  
Immobilized Trypsin ◽  
Esterolytic Activity ◽  
Derivatives Of

Thiosulfate derivatives, which can be reduced with mercaptoacetic acid, are suitable intermediates for the preparation of thiol derivatives of polymers. Thiosulfate derivatives of cellulose were prepared via chlorodeoxy- or via 3-chloro-2-hydroxy-propylcellulose, while mercaptodeoxycellulose prepared via chlorodeoxy derivative had more convenient properties for the immobilization of non-thiol enzymes (acetylcholine esterase, butyrylcholine esterase and trypsin). Before immobilization SH groups were introduced into choline esterases by i) reduction of the cystine residues, ii) reaction with methyl 4-mercaptobutyrimidate, and the isothiocyanate groups were introduced into trypsin on reaction with 3-isothiocyanatopropyl 1-isocyanate. The immobilization of the enzymes treated in this way was carried out under the conditions of the oxidation of thiol groups (i), thiol-disulfide exchange reaction (ii), or an addition nucleophilic reaction of isothiocyanates with thiols. In contrast to the proteolytic activity of the immobilized trypsin the esterolytic activity of immobilized choline esterases attained satisfactory values.

scholarly journals Managment of sulphur fertilizer in forage sorghum crop cultivated in eutrophic Cambisol with alkaline pH

2019 ◽  
pp. 1258-1266 ◽  
Author(s):  
Thiago Henrique Ferreira Matos Castañon ◽  
Boanerges Freire de Aquino ◽  
Edna Maria Bonfim Silva ◽  
Izabel Maria Almeida Lima ◽  
Ana Paula Alves Barreto Damasceno
Keyword(s):  
Elemental Sulfur ◽  
Chemical Properties ◽  
Dry Mass ◽  
Alkaline Ph ◽  
Single Superphosphate ◽  
Soil Fertilization ◽  
Forage Sorghum ◽  
Randomized Design ◽  
Sulphur Fertilizer ◽  
Completely Randomized Design

The objective of this study was to analyze the effect of soil fertilization with sulfur-based fertilizers, sulfate and elemental sulfur forms on biomass production, nutrient characteristics of sorghum and soil chemical properties. The experiment was carried out in a 4 x 4 factorial scheme (four sulfur sources: single superphosphate, agricultural gypsum, elemental sulfur powder and elemental sulfur granulated with bentonite, and four sulfur doses: 0, 40, 80, 120 mgdm-3) using four replications in a completely randomized design, being cultivated in pots under greenhouse conditions. The sorghum was cultivated for a period of 51 days after emergence of the seedlings. The shoot dry mass, shoot macronutrients content, root and soil and pH of the soil were evaluated. There were interactions between sources and sulfur doses in the variables such as shoot dry mass, sulfur in the root, sulfur and calcium in the soil. Elemental sulfur (granulate) showed lower concentrations of phosphorus, sulfur and N:S ratio in the shoot. The concentrations of potassium, calcium and magnesium did not show significant differences, both for the shoot and the root. The pH of the soil was reduced depending on the sources and doses of elemental sulfur. The sources and doses of sulfur did not influence the levels of phosphorus, potassium, and magnesium in the soil. The elemental sulfur in the form of powder is the best source of sulfur for forage sorghum cultivated in soil with alkaline pH.

scholarly journals Synthesis of monoketo and monohydroxy eicosanoic acids and esters with substituents at odd-numbered (3-13) carbons

2002 ◽  
Vol 67 (7) ◽  
pp. 473-480 ◽  
Author(s):  
Hulya Çelik
Keyword(s):  
Nmr Spectroscopy ◽  
High Purity ◽  
1H Nmr Spectroscopy ◽  
Methyl Esters ◽  
Chemical Properties ◽  
Physical And Chemical Properties ◽  
Keto Acids ◽  
Physical And Chemical ◽  
Derivatives Of ◽  
And Chemical Properties

In this study, monoketo and monohydroxy eicosanoic acids and their methyl esters with the position of the substituent on odd numbered carbon atoms from 3 to 13 were synthesized with high purity. Furthermore, the semicarbazone and anilide derivatives of the obtained keto acids were prepared. They were characterized by TLC, IR and 1H-NMR spectroscopy and their physical and chemical properties were established.

scholarly journals Synthesis and Anticancer Activity of CDDO and CDDO-Me, Two Derivatives of Natural Triterpenoids

Molecules ◽  
2019 ◽  
Vol 24 (22) ◽  
pp. 4097 ◽  
Author(s):  
Rebecca Borella ◽  
Luca Forti ◽  
Lara Gibellini ◽  
Anna De Gaetano ◽  
Sara De Biasi ◽  
...  
Keyword(s):  
Biological Effects ◽  
Chemical Properties ◽  
Cell Types ◽  
Telomerase Activity ◽  
Culture Cell ◽  
Protease Inhibition ◽  
Mitochondrial Functions ◽  
Anti Inflammatory ◽  
Apoptotic Pathways ◽  
Derivatives Of

Triterpenoids are natural compounds synthesized by plants through cyclization of squalene, known for their weak anti-inflammatory activity. 2-cyano-3,12-dioxooleana-1,9(11)-dien-28-oic acid (CDDO), and its C28 modified derivative, methyl-ester (CDDO-Me, also known as bardoxolone methyl), are two synthetic derivatives of oleanolic acid, synthesized more than 20 years ago, in an attempt to enhance the anti-inflammatory behavior of the natural compound. These molecules have been extensively investigated for their strong ability to exert antiproliferative, antiangiogenic, and antimetastatic activities, and to induce apoptosis and differentiation in cancer cells. Here, we discuss the chemical properties of natural triterpenoids, the pathways of synthesis and the biological effects of CDDO and its derivative CDDO-Me. At nanomolar doses, CDDO and CDDO-Me have been shown to protect cells and tissues from oxidative stress by increasing the transcriptional activity of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2). At doses higher than 100 nM, CDDO and CDDO-Me are able to modulate the differentiation of a variety of cell types, both tumor cell lines or primary culture cell, while at micromolar doses these compounds exert an anticancer effect in multiple manners; by inducing extrinsic or intrinsic apoptotic pathways, or autophagic cell death, by inhibiting telomerase activity, by disrupting mitochondrial functions through Lon protease inhibition, and by blocking the deubiquitylating enzyme USP7. CDDO-Me demonstrated its efficacy as anticancer drugs in different mouse models, and versus several types of cancer. Several clinical trials have been started in humans for evaluating CDDO-Me efficacy as anticancer and anti-inflammatory drug; despite promising results, significant increase in heart failure events represented an obstacle for the clinical use of CDDO-Me.

Parameters of the Bender Equation of State for Chloro Derivatives of Methane and Chlorobenzene

2001 ◽  
Vol 66 (6) ◽  
pp. 833-854 ◽  
Author(s):  
Ivan Cibulka ◽  
Lubomír Hnědkovský ◽  
Květoslav Růžička
Keyword(s):  
Experimental Data ◽  
Equation Of State ◽  
Virial Coefficient ◽  
Second Virial Coefficient ◽  
Virial Coefficients ◽  
Liquid Equilibrium ◽  
Second Virial Coefficients ◽  
Equilibrium Data ◽  
State Behaviour ◽  
Derivatives Of

Values of adjustable parameters of the Bender equation of state evaluated for chloromethane, dichloromethane, trichloromethane, tetrachloromethane, and chlorobenzene from published experimental data are presented. Experimental data employed in the evaluation included the data on state behaviour (p-ρ-T) of fluid phases, vapour-liquid equilibrium data (saturated vapour pressures and orthobaric densities), second virial coefficients, and the coordinates of the gas-liquid critical point. The description of second virial coefficient by the equation of state is examined.

Hydroxycinnamoyl: Coenzyme A Transferase Involved in the Biosynthesis of Kaempferol-3-(p-coumaroyl Triglucoside) in Pisum sativum

1977 ◽  
Vol 32 (9-10) ◽  
pp. 765-768 ◽  
Author(s):  
Marie H. Saylor ◽  
Richard L. Mansell
Keyword(s):  
Coenzyme A ◽  
Chemical Properties ◽  
Acyl Donor ◽  
Coumaric Acid ◽  
Enzyme Preparations ◽  
Naturally Occurring ◽  
Enzymatic Formation ◽  
Derivatives Of ◽  
Acid Esters ◽  
And Chemical Properties

Abstract The major flavonoids of Pisum are derivatives of kaempferol and quercetin, including both tri-glucosides and acylated triglucosides in which the acyl group is p-coumaric acid. Although hydroxy-cinnamic acid esters of flavonoids are common pigments in many plants, neither the enzymes nor the precursors involved in their biosynthesis have been demonstrated. We report here that crude enzyme preparations extracted from peas catalyze the transfer of the p-coumaroyl moiety of p-coumaroyl: Coenzyme A to kaempferol-3-triglucoside forming kaempferol-3-(p-coumaroyl triglucoside) as the acylated product. The reaction product has been vigorously shown to be identical to the naturally occurring kaempferol-3-(p-coumaroyl triglucoside) in both chromatographic and chemical properties. The enzymatic formation of the acylated derivative occurred only minimally when incubated with the cofactors required for carboxyl group activation (ligase) and maximally when incubated with p-coumaroyl : Coenzyme A as the acyl donor.

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