- "dual Layer" Self-Sorting with Cucurbiturils
-
Platinum(II) complexes bearing terpyridyl (tpy) and thiolate ligands were used to test the design of a "dual layer" self-sorting system in the presence of Cucurbit[8]uril (CB[8]). Pt(II) thiolates and CB[8] form 2:1 assemblies, with both metallic centers sitting on top of one another at one of the macrocycle portals. We showed that any pair of these CB[8]-secured Pt(II) complex dimers bearing different tpy "heads" and thiolate "tails" scrambles to afford up to 10 ternary assemblies via two processes: (1) supramolecular exchanges (i.e., the egression and ingression of Pt complexes from and into CB[8]) and (2) ligand exchanges between the Pt thiolates. The mixtures of 10 assemblies were fully characterized by nuclear magnetic resonance spectroscopy. While the thiolate tails do not significantly affect the rate of the supramolecular exchanges, they were found to control (1) the kinetics of ligand exchange, with bulkier thiolates causing dramatic rate retardations, as well as (2) the thermodynamics of the self-sorting process, i.e., the distribution of assemblies at equilibrium, via intra-CB[8] assembly interactions between pairs of thiolates. Ligand exchanges are consistently slower than supramolecular exchanges. An associative pathway that involves the formation of dimers of CB[8]-secured Pt dimers (a total of 4 Pt complexes) during the ligand exchange process was invoked to rationalize the observed kinetics.
- Barbero, Héctor,Masson, Eric,Thompson, Nathan A.
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supporting information
p. 867 - 873
(2020/02/20)
-
- Photoactivatable Odorants for Chemosensory Research
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The chemosensory system of any animal relies on a vast array of detectors tuned to distinct chemical cues. Odorant receptors and the ion channels of the TRP family are all uniquely expressed in olfactory tissues in a species-specific manner. Great effort has been made to characterize the molecular and pharmacological properties of these proteins. Nevertheless, most of the natural ligands are highly hydrophobic molecules that are not amenable to controlled delivery. We sought to develop photoreleasable, biologically inactive odorants that could be delivered to the target receptor or ion channel and effectively activated by a short light pulse. Chemically distinct ligands eugenol, benzaldehyde, 2-phenethylamine, ethanethiol, butane-1-thiol, and 2,2-dimethylethane-1-thiol were modified by covalently attaching the photoremovable protecting group (8-cyano-7-hydroxyquinolin-2-yl)methyl (CyHQ). The CyHQ derivatives were shown to release the active odorant upon illumination with 365 and 405 nm light. We characterized their bioactivity by measuring activation of recombinant TRPV1 and TRPA1 ion channels expressed in HEK 293 cells and the electroolfactogram (EOG) response from intact mouse olfactory epithelium (OE). Illumination with 405 nm light was sufficient to robustly activate TRP channels within milliseconds of the light pulse. Photoactivation of channels was superior to activation by conventional bath application of the ligands. Photolysis of the CyHQ-protected odorants efficiently activated an EOG response in a dose-dependent manner with kinetics similar to that evoked by the vaporized odorant amyl acetate (AAc). We conclude that CyHQ-based, photoreleasable odorants can be successfully implemented in chemosensory research.
- Gore, Sangram,Ukhanov, Kirill,Herbivo, Cyril,Asad, Naeem,Bobkov, Yuriy V.,Martens, Jeffrey R.,Dore, Timothy M.
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p. 2516 - 2528
(2020/10/02)
-
- Catalytic synthesis of dialkyl sulfides from dialkyl disulfides
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Dialkyl disulfides R2S2 where R = Me, Et, or Pr, both as individual compounds and as their mixtures, isolated from petroleum products can turn into alkanethiols and dialkyl sulfides under the action of catalysts having strong acid sites and medium-strength basic sites on their surface. In a helium atmosphere, the main conversion products are alkanethiols, while dialkyl sulfides form in low yield at a selectivity of no higher than 20%. A much higher dialkyl sulfide selectivity is attained in the reaction involving methanol. The most efficient catalyst for this reaction is alumina, with which the dialkyl sulfide selectivity is up to 99%.
- Mashkina,Khairulina
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p. 402 - 408
(2017/08/08)
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- C-S bond cleavage by a polyketide synthase domain
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Leinamycin (LNM) is a sulfur-containing antitumor antibiotic featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. The 1,3-dioxo-1,2- dithiolane moiety is essential for LNM's antitumor activity, by virtue of its ability to generate an episulfonium ion intermediate capable of alkylating DNA. We have previously cloned and sequenced the lnm gene cluster from Streptomyces atroolivaceus S-140. In vivo and in vitro characterizations of the LNM biosynthetic machinery have since established that: (i) the 18-membered macrolactam backbone is synthesized by LnmP, LnmQ, LnmJ, LnmI, and LnmG, (ii) the alkyl branch at C-3 of LNM is installed by LnmK, LnmL, LnmM, and LnmF, and (iii) leinamycin E1 (LNM E1), bearing a thiol moiety at C-3, is the nascent product of the LNM hybrid nonribosomal peptide synthetase (NRPS)-acyltransferase (AT)-less type I polyketide synthase (PKS). Sulfur incorporation at C-3 of LNM E1, however, has not been addressed. Here we report that: (i) the bioinformatics analysis reveals a pyridoxal phosphate (PLP)-dependent domain, we termed cysteine lyase (SH) domain (LnmJ-SH), within PKS module-8 of LnmJ; (ii) the LnmJ-SH domain catalyzes C-S bond cleavage by using L-cysteine and L-cysteine S-modified analogs as substrates through a PLP-dependent β-elimination reaction, establishing L-cysteine as the origin of sulfur at C-3 of LNM; and (iii) the LnmJ-SH domain, sharing no sequence homology with any other enzymes catalyzing C-S bond cleavage, represents a new family of PKS domains that expands the chemistry and enzymology of PKSs and might be exploited to incorporate sulfur into polyketide natural products by PKS engineering.
- Ma, Ming,Lohman, Jeremy R.,Liu, Tao,Shen, Ben
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p. 10359 - 10364
(2015/09/01)
-
- Design, Synthesis, and Characterization of Small-Molecule Reagents That Cooperatively Provide Dual Readouts for Triaging and, When Necessary, Quantifying Point-of-Need Enzyme Assays
-
A newly designed small molecule reagent provides both qualitative and quantitative readouts in assays that detect enzyme biomarkers. The qualitative readout enables rapid triaging of samples so that only samples that contain relevant concentrations of the target analyte must be quantified. The reagent is accessible in essentially three steps and 34% overall yield, is stable as a solid when heated to 44 °C for >1 month, and does not produce background signal when used in an assay. This paper describes the design and synthesis of the reagent, characterizes its response properties, and establishes the scope of its reactivity.
- Brooks, Adam D.,Mohapatra, Hemakesh,Phillips, Scott T.
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p. 10437 - 10445
(2015/11/18)
-
- Site-specific conjugation of RAFT polymers to proteins via expressed protein ligation
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Site-specific protein conjugates with RAFT polymers were synthesized using expressed protein ligation. Stable micelles were formed from both linear block copolymer and Y-shaped conjugates.
- Xia, Yan,Tang, Shengchang,Olsen, Bradley D.
-
supporting information
p. 2566 - 2568
(2013/04/23)
-
- Heterogeneous photocatalytic degradation of disulfoton in aqueous TiO 2 suspensions: Parameter and reaction pathway investigations
-
The photocatalytic degradation of organophosphorus insecticide disulfoton is investigated by having titanium dioxide (TiO2) as a photocatalyst. About 99% of disulfoton is degraded after UV irradiation for 90 min. The effects of the solution pH, catalyst dosage, light intensity, and inorganic ions on the photocatalytic degradation of disulfoton are also investigated, as well as the reaction intermediates which are formed during the treatment. Eight intermediates have been identified and characterized through a mass spectra analysis, giving insight into the early steps of the degradation process. To the best of our knowledge, this is the first study reporting the degradation pathways of disulfoton. The results suggest that possible transformation pathways may involve in either direct electron or hole transfer to the organic substrate. The photodegradation of disulfoton by UV/TiO2 exhibits pseudo-first-order reaction kinetics and a reaction quantum yield of 0.267. The electrical energy consumption per order of magnitude for photocatalytic degradation of disulfoton is 85 kWh/(m3 order).
- Chen, Ming-Hung,Chen, Chiing-Chang,Wu, Ren-Jang,Lu, Chung-Shin
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p. 380 - 390
(2013/07/27)
-
- Diels-Alder reactions of perfluoroketene dithioacetals with electron-rich 1,3-dienes: A new access to polysubstituted aromatic sulfides
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The present paper describes the Diels-Alder reactions of perfluoroketene dithioacetals with electron-rich 1,3-dienes (2,3-dimethylbuta-1,3-diene, isoprene, penta-1,3-diene) followed by spontaneous HF and thiol elimination, leading to polysubstituted aromatic sulfides in moderate to good yields. Reactions seem to be dependent on the substitution patterns of perfluoroketene dithioacetals; the best results were obtained from trifluoromethyl or pentafluoroethyl and ethylsulfanyl derivatives. Theoretical calculations performed at the DFT level are in good agreement with the experimental results and show that the overall process is controlled by the cycloaddition step.
- Bouillon, Jean-Philippe,Mykhaylychenko, Sergiy,Melissen, Sigismund,Martinez, Agathe,Harakat, Dominique,Shermolovich, Yuriy G.
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p. 8663 - 8669
(2012/10/29)
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- [[(tert-Butyl)dimethylsilyl]oxy]-methylGroup for sulfur protection
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Aromatic and aliphatic thiols can be protected by reaction with t-BuMe 2SiOCH2Cl in DMF in the presence of a base (2,6-lutidine or proton sponge); the resulting t-BuMe2SiOCH2SR or t-BuMe2SiOCH2SAr are deprotected by sequential treatment with Bu4NF and I2 to give symmetrical disulfides. Another mode of deprotection involves reaction with a sulfenyl chloride; this process gives an unsymmetrical disulfide and was examined with Me(CH2) 11SCH2OSiMe2Bu-t and three sulfenyl chlorides.
- Wang, Lihong,Clive, Derrick L. J.
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supporting information; experimental part
p. 1734 - 1737
(2011/06/09)
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- Standard enthalpies of formation of Li, Na, K, and Cs thiolates
-
The standard enthalpies of formation of alkaline metals thiolates in the crystalline state were determined by reaction-solution calorimetry. The obtained results at 298.15 K were as follows: δfH°m(MSR, cr)/kJ mol-1 = -259.0 ± 1.6 (LiSC2H5), -199.9 ± 1.8 (NaSC2H5), -254.9 ± 2.4 (NaSC4H9), -240.6 ± 1.9 (KSC2H 5), -235.8 ± 2.0 (CsSC2H5). These results where compared with the literature values for the corresponding alkoxides and together with values for δfH° m(MSR, cr) were used to derive a consistent set of lattice energies for MSR compounds based on the Kapustinskii equation. This allows the estimation of the enthalpy of formation for some non-measured thiolates.
- Leal, Joao P.
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experimental part
p. 441 - 446
(2010/08/04)
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- The Ever-surprising chemistry of boron: Enhanced acidity of phosphine·boranes
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The gas-phase acidity of a series of phosphines and their corresponding phosphine·borane derivatives was measured by FT-ICR techniques. BH 3 attachment leads to a substantial increase of the intrinsic acidity of the system (from 80 to 110 kJ mol-1). This acidity-enhancing effect of BH3 is enormous, between 13 and 18 orders of magnitude in terms of ionization constants. This indicates that the enhancement of the acidity of protic acids by Lewis acids usually observed in solution also occurs in the gas phase. High- level DFT calculations reveal that this acidity enhancement is essentially due to stronger stabilization of the anion with respect to the neutral species on BH3 association, due to a stronger electron donor ability of P in the anion and better dispersion of the negative charge in the system when the BH3 group is present. Our study also shows that deprotonation of ClCH2PH2 and ClCH 2PH2·BH3 is followed by chloride departure. For the latter compound deprotonation at the BH3 group is found to be more favorable than PH2 deprotonation, and the subsequent loss of Cl- is kinetically favored with respect to loss of Cl - in a typical SN2 process. Hence, ClCH2PH 2·BH3 is the only phosphine·borane adduct included in this study which behaves as a boron acid rather than as a phosphorus acid.
- Hurtado, Marcela,Yanez, Manuel,Herrero, Rebeca,Guerrero, Andres,Juan Z. Davalos,Jose-Luis, M. Abboud,Khater, Brahim,Guillemin, Jean-Claude
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supporting information; experimental part
p. 4622 - 4629
(2009/12/29)
-
- Process and catalyst for synthesis of mercaptans and sulfides from alcohols
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A process and catalyst blend for selectively producing mercaptans and sulfides from alcohols. The alcohol is reacted with hydrogen sulfide, in the presence of a catalyst blend containing a hydrotreating catalyst and a dehydration catalyst to convert the alcohol to mercaptan or sulfide in one-pass. The alcohols can include primary and secondary alcohols. The mercaptan or sulfide having less than about 30% unreacted alcohol contained therein.
- -
-
Page/Page column 5-7
(2008/06/13)
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- Catalytic method of producing alkyl mercaptans by adding hydrogen sulphide to an olefin
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The process for preparing a mercaptan from an olefin and hydrogen sulphide is carried out in the presence of hydrogen and a catalyst composition comprising a strong acid, such as a heteropolyacid, and at least one metal belonging to group VIII of the Periodic Table.
- -
-
Page/Page column 3
(2008/06/13)
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- Catalytic method of producing mercaptans from thioethers
-
The process for preparing a mercaptan from a thioether and hydrogen sulphide is carried out in the presence of hydrogen and a catalyst composition comprising a strong acid, such as a heteropolyacid, and at least one metal belonging to group VIII of the Periodic Table.
- -
-
Page/Page column 3; 4
(2008/06/13)
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- Kinetics and mechanism of the nucleophilic substitution of tellurium(II) dialkanethiolates, Te(SR1)2 with thiols, HSR2
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The equilibrium reaction between tellurium(II) dithiolates and thiols, Te(SR1)2 + 2 HSR2 ? Te(SR 2)2 + 2 HSR1 was studied by means of 1H- and 125Te NMR spectroscopy and ab initio quantum chemical methods. It was found that the reaction is catalyzed by Bronsted acids and bases, the catalytic activity corresponding to the strength of the respective acid or base. Investigation of the initial step of the reaction, Te(SR1)2 + HSR2 ? Te(SR 1)(SR2) + HSR1, showed it to proceed according to first order kinetics for Te(SR1)2, HSR2 and for the catalyst. Ab initio geometry optimizations and frequency calculations suggest [Te(SR1)(HSR1)(HSR2)]+ and [Te(SR1)2(SR2)]- to be stable intermediates and not transition states in the acid and base catalyzed reactions, respectively. The reaction hence proceeds via an additional elimination rather than an SN2 mechanism. The catalytic activity displayed by acids and bases can be applied to reduce the temperature in synthesis of thermally labile tellurium(II) dithiolates. Copyright Taylor & Francis Inc.
- Fleischer, Holger
-
p. 815 - 825
(2007/10/03)
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- Semi-continuous photochemical method and device therefor
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In the photochemical synthetic process in semi-continuous mode according to the invention, a reactor comprising two zones is used, the radiating portion of the lamp(s) being totally immersed in a first zone which is completely filled with reaction medium and spills off via an overflow into a second zone whose volume is sufficient to contain the volume of reaction medium originating from the first zone and corresponding substantially to the volume of the reagent(s) gradually introduced.
- -
-
Page/Page column 2
(2008/06/13)
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- Biomimetic thiolate alkylation with zinc pyrazolylbis(thioimidazolyl)borate complexes
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The NS2ZnX coordination in thiolate-alkylating zinc enzymes is reproduced in (tripod)ZnX complexes with substituted pyrazolylbis(thioimidazolyl)borate tripod ligands. Intermediate (tripod)Zn nitrates and perchlorates are converted into (tripod) Zn thiolates, including the biologically relevant homocysteinate. Methylation with CH3I converts these to (tripod)ZnI and the corresponding thioethers CH3SR, including methionine. A kinetic investigation has shown the alkylations to be intramolecular SN2 processes that take place at the zinc-bound thiolates. They are considerably faster for the (NS2)Zn thiolates than for the (N2S)- and (N3)Zn-thiolates with similar pyrazolylborate-derived tripod ligands, in agreement with Nature's choice of an NS2 donor set for zinc. Wiley-VCH Verlag GmbH & Co. KGaA, 2005.
- Ibrahim, Mohamed M.,He, Guosen,Seebacher, Jan,Benkmil, Boumahdi,Vahrenkamp, Heinrich
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p. 4070 - 4077
(2007/10/03)
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- First synthesis and characterization of vinylselenols and vinyltellurols
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Vinylselenols and vinyltellurols have been prepared by slow addition of tributyltin hydride to the corresponding divinyldiselenide or divinylditelluride in tetraglyme.
- Guillemin, Jean-Claude,Bouayad, Asmae,Vijaykumar, Dange
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p. 1163 - 1164
(2007/10/03)
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- A rapid and efficient cleavage of organic disulfides to mercaptans using ZrCl4/NaBH4
-
A practical and cheaper reagent system ZrCl/NaBH4 is used for the reductive cleavage of organic disulfides to mercaptans under mild conditions, in excellent yields.
- Purushothama Chayr,Rajaram,Iyengar
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p. 3905 - 3911
(2007/10/03)
-
- Delineation and decomposition of energies involved in quaternary ammonium binding in the active site of acetylcholinesterase
-
The quaternary ammonium binding locus in the active site of mammalian acetylcholinesterase is subtended by the side chains of Trp86, Tyr133, Glu202, and Tyr337. Linear free-energy relationships define the interactions involved in molecular recognition by mouse acetylcholinesterase of the quaternary ammonium moiety of ligands. For substrates CH3C(=O)XCH2CH2Y [X = O, Y = CHMe2, or CH2CH3; X = S, Y = H, NH+Me2, or N+Me3] and trifluoroacetophenone transition state analogue inhibitors m-YC6H4C(=O)CF3 [Y = H, Me, Et, iPr, tBu, CF3, NH2, NO2, NMe2, or N+Me3], log(k(cat)/K(m)) and pK(i) depend linearly on the molar refractivity, but not the hydrophobicity, of the substituents Y. These correlations indicate that, in the acylation stage of catalysis, interactions in the quaternary ammonium binding locus stabilize the tetrahedral intermediate (as modeled by transition state analogue affinity) by (5 x 105)-fold (ΔΔG(TI) = -32.5 kJ mol-1) and the transition state by (2 x 104)-fold (ΔΔG(+) = -24.5 kJ mol-1). To evaluate the contribution of cation-π interactions, Trp86 was convened into Tyr, Phe, and Ala by site-specific mutagenesis. For this set of enzymes, a linear free-energy relationship is observed between the pK(i) values for inhibitions by the respective neutral and cationic transition state analogue inhibitors, m-tert-butyltrifluoroacetophenone and m-(N,N,N- trimethylammonio)-trifluoroacetophenone, which indicates that the free energy released on interaction of the quaternary, ammonium moiety with Trp86 arises about equally from cation-π and charge-independent interactions.
- Quinn, Daniel M.,Feaster, Shawn R.,Nair, Haridasan K.,Baker, Nathan A.,Radic, Zoran,Taylor, Palmer
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p. 2975 - 2980
(2007/10/03)
-
- Hydrolysis and aminolysis of alkyl xanthate esters and cellulose analogues
-
The hydrolysis and aminolysis of a series of S-substituted O-alkylxanthate esters was studied in 20% v/v aqueous methanol at 35°C. The pH-rate profiles of the hydrolyses showed water and hydroxide-ion-catalyzed reactions. The reaction of 2,4-dinitrophenyl cellulose xanthate (CelXDNP) and p-nitrobenzyl cellulose xanthate (CelXNB) with polyalanine and lysozyme produced a covalent bond between the polypeptide and the cellulose matrix, as shown by solid-state 13C NMR. However, the nature of the bonding could not be identified. The reaction of nucleophiles (H2O, OH-, RNH2) and xanthic esters was consistent with an addition-elimination mechanism through a tetrahedral intermediate. Bronsted plots against the pKa of the nucleophile (βnu) or the nucleofuge of the substrate (βlg) were used to characterize the rate-determining step. The pKa values of the nucleophiles ranged between -1.74 and 15.74, and for the nucleofuges, they were in the range of 10.50-0.92. For nucleophiles with pKa values up to about 10, βlg was 0.10-0.15, and βnu changed from 0.48 to 0.35 for the strongest electron-withdrawing nucleofuge. It was concluded that the water-catalyzed hydrolyses, and also aminolyses with moderately basic amines, occur with rate-determining formation of the tetrahedral intermediate. For strong bases such as hydroxide ion, the disappearance of the intermediate becomes the slowest step. The reaction of cellulose xanthic esters with external nucleophiles as hydroxide ion and amines shows simple first-order kinetics and is slower than alkyl or sugar xanthates, probably due to the diffusion effect through the tight cybotactic region of cellulose.
- Humeres, Eduardo,Soldi, Valdir,Klug, Marilene,Nunes, Mauricea,Oliveira, Celia M.S.,Barrie, Patrick J.
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p. 1050 - 1056
(2007/10/03)
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- A new method for rapidly generating inhibitors of glyoxalase I inside tumor cells using S-(N-aryl-N-hydroxycarbamoyl)ethylsulfoxides
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The enediol analogue S-(N-p-chlorophenyl-N-hydroxycarbamoyl)glutathione is a powerful mechanism-based competitive inhibitor of the anticancer target enzyme glyoxalase I. Nevertheless, this compound exhibits limited toxicity toward tumor cells in vitro because it does not readily diffuse across cell membranes. We describe an efficient method for indirectly delivering the enzyme inhibitor into murine leukemia L1210 cells via acyl interchange between intracellular glutathione and the cell-permeable prodrug S-(N-p- chlorophenyl-N-hydroxycarbamoyl)ethylsulfoxide. The second-order rate constant for the acyl-interchange reaction in a cell-free system is 1.84 mM- 1 min-1 (100 mM potassium phosphate buffer, 5% ethanol, pH 7.5, 25 °C). Incubation of L1210 cells with the sulfoxide in vitro results in a rapid increase in the intracellular concentration of the glyoxalase I inhibitor (k(app) = 1.41 ± 0.03 min-1 (37 °C)) and inhibition of cell growth (GI50 = 0.5 ± 0.1 μM). This represents an improvement in both efficiency and potency over the dialkyl ester prodrug strategy in which the inhibitor is indirectly delivered into tumor cells as the [glycyl,glutamyl] diethyl or dicyclopentyl esters. The fact that π-glutathione transferase catalyzes the acyl-interchange reaction between GSH and the sulfoxide suggests that the sulfoxide, or related compounds, might exhibit greater selective toxicity toward tumor cells that overexpress the transferase.
- Hamilton, Diana S.,Kavarana, Malcolm J.,Sharkey, Ellyn M.,Eiseman, Julie L.,Creighton, Donald J.
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p. 1823 - 1827
(2007/10/03)
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- Synthesis of organophosphorus compounds in terms of elemental phosphorus, sulfur and their derivatives
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We have developed new facile methods for synthesizing various organophosphorus compouds on the basis of elemental phosphorus and sulfur, phosphorus sulfides and esters of thiophosphorous acids.
- Batyeva, Elvira S.,Nizamov, Il'yas S.,Kursheva, Lidiya I.,Frolova, Liliya V.
-
-
- METHOD FOR TREATING ANXIETY WITH MUSCARINIC CHOLINERGIC RECEPTOR AGONISTS
-
The present invention relates a method for treating anxiety using azacyclic and azabicyclic pyrazine compounds.
- -
-
-
- High-Temperature Organic Synthesis. XLV. Generation of Vinylthio Radicals from Alkyl 2-Chloroalkyl Sulfides, Bis(2-chloroalkyl) Sulfides, and Alkyl Vinyl Sulfides
-
Bis(2-chloroethyl) sulfide, 2-chloroethyl ethyl sulfide, and alkyl vinyl sulfides produce vinylthio radical in the gas phase. Thermolysis of these sulfides in the presence of acetylene at 500-600°C yield thiophene via addition of vinylthio radicals to acetylene. Butyl vinyl sulfide is the best source of vinylthio radicals (the yield of thiophene reaches 76%). Mechanisms of these reactions and approaches to thiophene synthesis are discussed. A convenient laboratory procedure for preparation of thiophene is proposed.
- Deryagina,Levanova,Sukhomazova,Voronkov
-
-
- Use of azacyclic or azabicyclic pyrazine compounds for treating anxiety
-
The present invention relates a method for treating anxiety using azacyclic and azabicyclic pyrazine compounds.
- -
-
-
- Thiyl radicals in gas-phase thermolysis of xanthic acid esters
-
Gas-phase thermolysis of xanthic acid esters and their reaction with acetylene at 250-600°C have been studied for the first time. The direction of the thermolysis is determined by the nature of the substituents at the oxygen and sulfur atoms. The main products of the thermolysis are gaseous hydrocarbons, carbon monoxide and hydrogen sulfide. The yields of liquid products of the thermolysis and of the reactions with acetylene are 4-46 %. The role of thiyl radicals in thiophene molecule formation and reaction routes to carbon disulfide, dithiocarbonates, and stilbene are discussed.
- Deryagina,Korchevin,Russavskaya,Sukhomazova,Levanova
-
p. 140 - 143
(2007/10/03)
-
- NO-Group transfer (transnitrosation) between S-nitrosothiols and thiols. Part 2
-
The kinetics of NO-group transfer have been measured for the reaction between a nitrosothiol (HOCH2CH2SNO) and nine thiols, mostly based on the cysteine structure.The reaction is second-order and there is evidence for a steric effect for thiols containing 1,1-dimethyl substituents (penicillamine derivatives).Reaction occurs via the thiolate anion as shown by the pH-rate constant profile, and a full kinetic analysis for the reactions of two thiols (N-acetylcysteine and glutathione) is quantitatively in agreement with this mechanism.Variation of the nitrosothiol structure for reaction with N-acetylcysteine shows that electron-withdrawing substituents in the nitrosothiol promote reaction; there is a similarity with the corresponding reactions of alkyl nitrites.
- Barnett, D.Jonathan,Rios, Ana,Williams, D. Lyn H.
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p. 1279 - 1282
(2007/10/03)
-
- Kinetics and Mechanism of the Acid-Catalysed Hydrolysis of Benzaldehyde Diaryl Thioacetals and of Benzaldehyde S-Aryl, S-Ethyl Acetals in Aqueous Perchloric Acid
-
The effects on the rate of hydrolysis of changes in aryl substituents, acid concentration, temperature, and solvent isotope, show that the acid-catalysed hydrolyses of five benzaldehyde diaryl thioacetals and three benzaldehyde S-aryl, S-ethyl acetals in 2-7 mol dm-3 aqueous perchloric acid proceed via essentially A1 mechanisms.The pattern of the substituent effects found for the leaving, and remaining, S-aryl groups is similar to that found previously for leaving and remaining groups in O,O- and O,S-acetals.
- Ali, Muhammad,Satchell, Derek P. N.
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p. 1825 - 1828
(2007/10/02)
-
- Kinetic and Equilibrium Studies of ?-Adduct Formation and Nucleophilic Substitution in the Reactions of Ethyl Thiopicrate with Aliphatic Amines in Dimethyl Sulfoxide
-
Kinetic and equilibrium results are reported for the reaction of ethyl thiopicrate with butylamine, pyrrolidine and piperidine in dimethyl sulfoxide.The most rapid reaction involves attack at the unsubstituted 3-position to give anionic ?-adducts.The rate-limiting step in this process changes from nucleophilic attack by amine with butylamine to proton transfer from the zwitterionic intermediate with piperidine; pyrrolidine shows intermediate behaviour.Attack by amine at the 1-position results in displacement of the ethylthio group, although intermediates are notobserved during this process.It is suggested that base catalysis observed in the reaction with pyrrolidine may result from rate-limiting proton transfer from the zwitterionic intermediate. 1H NMR measurements using 0.1 mol dm-3 solutions of substrate show that the displaced ethanethiolate ion may attack ring-carbon atoms of either unreacted substrate or substitution products.
- Chamberlin, Rachel,Crampton, Michael R.
-
-
- S-ethyl thiooctanoate as acyl donor in lipase catalysed resolution of secondary alcohols
-
The use of S-ethyl thiooctanoate as acyl donor in resolution of secondary alcohols by lipase catalysed transesterification, resulted in an efficient displacement of the equilibrium towards esterification of the alcohol. A lipase (component B) from Candida antarctica was used as the catalyst. On a semi-preparative scale, 0.5 g of 2-octanol was resolved in less than one hour, affording an enantiomeric excess of >98% of the remaining alcohol and >97% of the produced ester. Three other alcohols, 1-phenyl ethanol, 1-cyclohexyl ethanol and trans-2-methyl cyclohexanol were also resolved with good optical yields. After 50% conversion on a preparative scale, 15 g of alcohol, the (S)-enantiomer of 2-octanol could be obtained with an enantiomeric excess of 96%. The (R)-enantiomer was isolated with an enantiomeric excess of 97% after hydrolysis of the produced ester.
- Frykman,Ohrner,Norin,Hult
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p. 1367 - 1370
(2007/10/02)
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- Kinetic and Equilibrium Studies of ?-Adduct Formation and Nucleophilic Substitution in the Reactions of Hydroxide Ions with 2,4,6-Trinitrophenyl Sulfides and Ethers
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Kinetic and equlibrium data are reported for reaction of hydroxide ions in 20/80 DMSO/water (v/v) with a series of 4'-substituted phenyl 2,4,6-trinitrophenyl sulfides, 1, and with ethyl thiopicrate, 2, ethyl picrate, 3, phenyl picrate, 4, and 1,3,5-trinitrobenzene, 5.In each case a rapid reaction is observed involving reversible hydroxide addition at an unsubstituted ring-position.In the case of 1-4 this is followed by slower, irreversible attack at the 1-position leading to the formation of picric acid.The Hammett ρ value for equilibrium addition of hydroxide to the 3-position of 1 is 0.98, and the ρ value for rate constants for attack at the 1-position is 0.62.The results are discussed in terms of the electronic and steric effects of the 1-substituents.Comparison of 1-5 indicates that changing from an OR to SR group introduces additional steric crowding.However for the reactions studied changing from R = Et to R = Ph has little steric consequence.
- Chamberlin, Rachel,Crampton, Michael R.,Knight, Roland L.
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p. 2986 - 2998
(2007/10/02)
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- Kinetics of Hydrolysis of 2-Aryl-2-phenyl-1,3-dithianes in 10percent (v/v) Dioxane-Water, Containing Perchloric Acid. Acidity Functions in this Solvent and the Reactivity of α-Thio Carbocations
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The acid-catalysed hydrolysis of 2-aryl-2-phenyl-1,3-dithianes in 10percent (v/v) dioxane-water occurs at a convenient rate at 25 deg C in the presence of 5-8 mol dm-3 perchloric acid.The effect on the rate of changes in substituents, acidity and temperature, and of the use of a deuteriated solvent are described.Measurements of the H0 and X acidity functions for the solvent are reported; their values are very similar to those found for pure water over most of the acidity range.The mechanism of hydrolysis is believed to change from an ASE2 scheme for the most reactive dithianes to an A2-like scheme for the least reactive.In very concentrated acid solutions the dithianes (and other suitable S,S-acetals) lead to stoichiometric amounts of the α-thio carbocations often postulated as low-concentration intermediates in S,S-acetal hydrolysis.The kinetics of the reaction of these ions with water to give the benzenophenone (or corresponding carbonyl compound) are described, and compared with findings for similar α-oxo carbocations.Previous views on the mechansim of this reaction are criticised.
- Ali, Muhammad,Satchell, Derek P. N.,Le, Vu T.
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p. 917 - 922
(2007/10/02)
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- Chemical Reactions Mediated by Heavy Metal Ions. 2. Mercury Ligation Effects on the Hg(II)-Promoted Hydrolyses of Benzaldehyde O-Ethyl S-Ethyl and S-Phenyl Acetals
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The kinetics of the mercury(II)-promoted hydrolyses of acyclic O,S-acetals of benzaldehyde have been measured to establish that (i) mercury(II) is a reagent, not a catalyst, in the hydrolysis reaction, (ii) the rate-limiting step can be any of the three steps in Scheme I (khemi, kHg, or kacetal), depending on the concentration of mercury(II) relative to the acid, and (iii) the state of complexation of mercury(II) is critical to its reactivity.Part 1 of this series established the "standard state" for all further work; this paper utilized the same controls and safeguards.The second-order rate constants for hydrolysis of benzaldehyde O-ethyl S-ethyl acetal promoted by Hg2+, HgCl+, HgBr+, or HgI+ is at the diffusion limit (109 M-1 s-1).Rate constants for HgCl2, HgBr2, HgI2, HgCl3-, and HgI3- are 106, 105, 102, 104, and 50 M-1 s-1, respectively.Rate constants for hydrolysis of benzaldehyde O-ethyl S-phenyl acetal are the same, within experimental error, except for perhaps the least reactive reagents.Thus, although reagents differ in reactivity by 107, the reactivity toward a SEt moiety is equal to the reactivity toward a SPh moiety.A detailed mechanism is presented in which the rate-limiting step does not involve carbon-sulfur bond heterolysis, but rather one of the mercury ligation steps.
- Jensen, James L.,Maynard, David F.,Shaw, Gregory R.,Smith, Tyrrell W.
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p. 1982 - 1986
(2007/10/02)
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- Kinetics and Mechanism of the Hydrolysis of Diethyl Thioacetals of Substituted Benzaldehydes in Aqueous Perchloric Acid
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Substituent effects, activation parameters, acidity dependencies and solvent isotope effects suggest that the acid-catalysed hydrolysis of diethyl thioacetals of meta- and para-substituted benzaldehydes, and of acetophenone, proceed via an essentially A1 scheme.The extent of C-S bond cleavage in the transition state may become progressively greater on moving from the least to the most reactive acetals.The use of the excess acidity as a criterion of mechanism is briefly discussed.Activation enthalpies and entropies are significantly larger for the meta-substituted acetals.Our results are compared with existing data for the O,O- and O,S-analogues.
- Ali, Muhammad,Satchell, Derek P. N.
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p. 575 - 578
(2007/10/02)
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- Mitomycin derivatives
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Novel mitomycin derivatives are characterized by a substituent on the C6 -methyl group. The mitomycin derivatives exhibit anti-tumor and antibacterial activity and have low toxicity.
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- Facile Elimination of Ethanethiol in the Reaction of α-Hydroxy-β-bis(ethylthio)acetals with Copper(I) Chloride in Dimethylformamide
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Bis(ethylthio)acetals possessing a hydroxy group in the α-position eliminate, upon reaction with copper(I) chloride in dimethylformamide, cleanly and quantitatively one molecule of ethanethiol with the formation of substituted ethyl vinyl sulfides.
- Paryzek, Zdzislaw,Martynow, Jacek
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p. 618 - 620
(2007/10/02)
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- HIGH-TEMPERATURE ORGANIC SYNTHESIS XXXII. REACTION OF ACETYLENE WITH LOWER DIALKYL POLYSULFIDES
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Dimethyl disulfide and diethyl di-, tri-, and tetrasulfides or their mixtures react with acetylene in the gas phase at 470-520 deg C with the formation of thiophene and isomeric thienothiophenes as the main products (with overall yields of up to 85percent).The reaction mechanism, involving the formation of vinylthiyl radicals, is discussed.
- Voronkov, M. G.,Deryagina, E. N.,Ostroukhova, L. A.,Korchevin, N. A.,Sukhomazova, E. N.,et al.
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p. 2320 - 2322
(2007/10/02)
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- Thiolate, Thioether, and Thiol Derivatives of Iron(0) Carbonyls
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A new series of anionic complexes of iron tetracarbonyl monofunctionalized with the ligand ->,-> (R = Ph, Et, Me, H), have been synthesized and characterized.The compound was formed in the reaction of and PhSSPh.The -> anion was characterized by X-ray diffraction as its +> salt and found to be a typical trigonal-bipyramidal complex in which the phenylthiolate ligand occupies an axial position with a Fe-S bond distance of 2.332(5) Angstroem and Fe-S-C(Ph) = 111.3(6) deg.The salt crystallized inthe orthorhombic space group Pbc21, with a = 9.529(4) Angstroem, b = 21.493(9) Angstroem, c = 20.185(9) Angstroem, V = 4134(3) Angstroem3, and Z = 2.Other members of the series of complexes, ->, were best obtained by ligand exchange of -> and the labile thioether complex (PhSMe)Fe(CO)4.The latter was produced from the low-temperature alkylation of the ->.Protonation of the thiolates (R = Ph, Et, Me, H) ultimately leads to formation of H2 and Fe2(μ-SR)2(CO)6; however, the intermediate thiol, (RSH)Fe(CO)4, could be observed at -78 to -40 deg C for R = Et, Me.The PhSH and HSH derivatives were unstable even at -78 deg C.
- Liaw, Wen-Feng,Kim, Christine,Darensbourg, Marcetta Y.,Rheingold, Arnold L.
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p. 3591 - 3597
(2007/10/02)
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- Reduction of n-C5H11N3 catalyzed by single cubane clusters with Mo-Fe-S and Fe-S cores, mediated with methyl viologen in aqueous micellar solutions
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The Mo-Fe-S double cubane cluster [Mo2Fe6S8(SC6H 4-p-n-C8H17)6(O2C 6Cl4)2]4- bridged by two SC6H4-p-n-C8H17-- anions is dissociated into two [MoFe3S4(SC6H4-p-n-C 8H17)3(O2C6Cl 4)L]2- (1; L = DMF, Me2CO) single cubane clusters in polar organic solvents, such as DMF and Me2CO. The solvent molecule coordinated to the molybdenum of the MoFe3S4 core is easily substituted by n-C5H11N3. In the corresponding single cubane cluster with the Fe4S4 core, [Fe4S4(SC6H4-p-n-C8H 17)4]2- (2), however, the thiolate ligand is substituted by n-C5H11N3 only in the reduced 3- state. Both 1 and 2 function as catalysts for the reduction of n-C5H11N3 by Na2S2O4 in aqueous Triton X-100 micellar solutions, giving an equal amount of n-C5H11NH2 and N2. The reduction is enhanced efficiently by the addition of methyl viologen dication (MV2+). The MV.+ radical cation formed by the reduction of MV2+ with Na2S2O4 effectively transfers electrons to 1 to reduce n-C5H11N3 not only with two electrons but also with six and eight electrons, affording N2H4 and NH3 as well as n-C5H11NH2 and N2. On the other hand, 2 catalyzes only the two-electron reduction even in the presence of MV2+ to give n-C5H11NH2 and N2, suggesting that 1 is superior to 2 as a catalyst for the multielectron reduction of n-C5H11N3.
- Tanaka, Koji,Moriya, Makoto,Uezumi, Satoshi,Tanaka, Toshio
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p. 137 - 143
(2008/10/08)
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- NEW SYNTHESIS OF 1,2,5-SELENADIAZOLES
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A new synthesis of 1,2,5-selenadiazoles which starts from unsubstituted or monosubstituted 1,2,5-thiadiazoles and Grignard reagents is described and the mechanism of the reaction discussed.
- Bertini, Vincenzo,Munno, Angela De,Picci, Nevio,Lucchesini, Francesco,Pocci, Marco
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p. 2153 - 2158
(2007/10/02)
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- Structure-Stability Relationships in Vinyl Sulfides. I. On the Stable Conformations of Vinyl Sulfides
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A thermodynamic and 13C NMR spectroscopic study of the structures of the less stable rotamers of alkyl vinyl sulfides have been performed.It has been shown that the less stable rotamer of methyl vinyl sulfide has the planar s-trans configuration and the proportion of this is about 20percent.The energy difference between the planar s-cis and s-trans is about 3.5 kJ mol-1.Ethyl vinyl sulfide is almost an equimolar mixture of the planar s-cis and s-trans conformations.The 13C NMR data showed that the p-? cojugation in the compounds that could not adopt any of the planar arrangements was decreased.In alkyl 1-propenyl sulfides, the stabilizing interaction between the methyl group and the S atom cis to each other was ca.1.8 kJ mol-1.The most probable choice for the most stable conformation of di-1-propenyl sulfides is the planar (or nearly planar) s-trans,s-trans one.
- Virtanen, Reijo
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p. 313 - 327
(2007/10/02)
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- Chemical Consequences of the Intramolecular Interaction between a Sulphur Atom and a Methoxycarbonyl Group in Fluorene Systems
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The intramolecular interaction between a sulphur atom and a methoxycarbonyl group was found to affect their chemical reactivity.The rates of C-S bond cleavage in methyl-9,9-bis(ethylthio)fluorene-x-carboxylate, where x is 1, 2, or 3, with sodium ethanethiolate show that the rate is minimal, though comparable with the others, when x=1, because of steric effects.In contrast, methyl 9-(ethylthio)fluorene-x-carboxylates, where x=1, 2, or 3, exhibit the maximum rate when x=1.The rates of ester exchange in the presence of toluene-p-sulphonic acid indicate that the reaction is accelerated by the presence of two ethylthio groups at the 9 position of methyl fluorene-1-carboxylate but no significant effect is detected if there is only one ethylthio group.The hydrolysis of the thioketal group in 9,9-bis(ethylthio)fluorene is also accelerated by the presence of a 1-methoxycarbonyl group.The implication of these results are discussed with the use of a model compound.
- Nakanishi, Waro,Kusuyama, Yoshiaki,Ikeda, Yoshitsugu,Oki, Michinori
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p. 799 - 804
(2007/10/02)
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- One-Flask Synthesis of Sulfides from Alcohols and Alkyl Halides Using Benzoxazoline-2-thione
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The synthesis of sulfides from alcohols and benzoxazoline-2-thione (I) was studied to establish its generality and the mechanism of the reaction.A one-flask synthesis of sulfides from alcohols was developed.According to this procedure, various sulfides were prepared without the use of illsmelling thiols.Moreover, partial sulfenylation of diols to give sulfenyl alcohols was achieved.Keywords - one-flask synthesis; benzoxazoline-2-thione; partial sulfenylation; sulfide; sulfenyl alcohol
- Takeuchi, Yasuo,Sakagawa, Keiko,Kubo, Masumi,Yamato, Masatoshi
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p. 1323 - 1327
(2007/10/02)
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- Fibre-reactive dyes, containing both chloro and fluoro triazine radicals
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Fibre-reactive dyes of the formula STR1 wherein D is the radical of a benzene or naphthalene azo dye which contains sulpho groups, each of R1, R2 and R3 is a hydrogen atom, B is an arylene group and A is an amino group.
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- Solvent Isotope Effects on Formation of Protease Complexes with Inhibitory Aldehydes, with an Appendix on the Determination of Deuterium Fractionation Factors by NMR
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In both CCl4 and water, equilibria of addition of thiols to acetaldehyde are strongly favored by the presence of deuterium at exchangeable positions, whereas equilibria of addition of hydroxylic compounds are hardly affected.To test the possibility of using solvent isotope effects for diagnosing the structure of enzyme-inhibitor complexes, we examined the influence of D2O on the interaction of proteases with inhibitory aldehydes.Equilibrium constants for binding of inhibitory aldehydes showed enhancements in D2O of 1.32+/-0.12 for α-chymotrypsin and 2.65+/-0.14 for papain, slightly in excess of those expected for covalent addition of an alcohol or thiol, respectively.In an Appendix, hydroxylic solutes are shown to alter the magnetic susceptibilities of solutions, resulting in systematic errors in apparent fractionation factors of their exchangeable protons as determined by conventional NMR procedures.As a result, apparent fractionation factors change with the orientation of the magnetic field.Corrected values for hydroxylic protons, determined by other methods, differ only slightly from unity.
- Bone, Roger,Wolfenden, Richard
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p. 4772 - 4777
(2007/10/02)
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