- Mild and eco-friendly chemoselective acylation of amines in aqueous medium using a green, superparamagnetic, recoverable nanocatalyst
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Copper-grafted guanidine acetic acid-modified magnetite nanoparticles (Fe3O4@GAA-Cu(II)) as a green, superparamagnetic and recoverable nanocatalyst is found to promote quantitative N-acylation of various amines in a very short time with an equimolar amount of thioacetic acid in water at room temperature. This method is found to be highly selective for amines and not sensitive to other functional groups. Mild reaction condition, high selectivity, efficiency, simple workup and excellent yields are some of the major advantages of the procedure.
- Miraki, Maryam Kazemi,Yazdani, Elahe,Ghandi, Leila,Azizi, Kobra,Heydari, Akbar
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- Feed additive method for preparing DL-tryptophan
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The invention provides a method for preparing a feed additive DL-tryptophan. The method comprises the following steps of: 1) preparing indole-3-formaldehyde; 2) preparing aceturic acid; 3) preparing 3-indolyl-2-acetamino acrylic acid; 4) preparing N-acetyltryptophan; 5) preparing the DL-tryptophan. The method for preparing the feed additive DL-tryptophan is easy in acquisition of raw materials, low in raw material cost, high in reaction efficiency, and simple in process; the method can be carried out at the normal temperature and under the normal pressure without environmental pollution.
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Paragraph 0027; 0035; 0036
(2016/10/07)
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- Synthesis of tripeptides containing d-Trp substituted at the indole ring, assessment of opioid receptor binding and in vivo central antinociception
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The noncationizable tripeptide Ac-d-Trp-Phe-GlyNH2 was recently proposed as a novel minimal recognition motif for μ-opioid receptor. The introduction of different substituents (methyl, halogens, nitro, etc.) at the indole of d-Trp significantly influenced receptor affinities and resulted in serum stability and in a measurable effect on central antinociception in mice after ip administration.
- De Marco, Rossella,Bedini, Andrea,Spampinato, Santi,Gentilucci, Luca
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supporting information
p. 6861 - 6866
(2014/10/15)
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- Synthesis and evaluation of β-carboline derivatives as inhibitors of human immunodeficiency virus
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A series of β-carboline derivatives were synthesized by utilizing aromatization and chemoselective alkylation method recently reported from our laboratory. Synthesized derivatives were evaluated for anti-HIV activity in human CD4+ T cell line (CEM-GFP) infected with HIV-1 NL4.3 virus. 1-Formyl-β-carboline-3-carbxylic acid methyl ester (15) showed inhibition of human immunodeficiency virus at IC50 = 2.9 μM.
- Brahmbhatt, Keyur G.,Ahmed, Nafees,Sabde, Sudeep,Mitra, Debashis,Singh, Inder Pal,Bhutani, Kamlesh K.
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body text
p. 4416 - 4419
(2010/09/18)
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- The biosynthetic pathway of crucifer phytoalexins and phytoanticipins: De novo incorporation of deuterated tryptophans and quasi-natural compounds
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Although several biosynthetic intermediates in pathways to cruciferous phytoalexins and phytoanticipins are common, questions regarding the introduction of substituents at N-1 of the indole moiety remain unanswered. Toward this end, we investigated the potential incorporations of several perdeuterated d- and l-1′-methoxytryptophans, d- and l-tryptophans and other indol-3-yl derivatives into pertinent phytoalexins and phytoanticipins (indolyl glucosinolates) produced in rutabaga (Brassica napus L. ssp. rapifera) roots. In addition, we probed the potential transformations of quasi-natural compounds, these being analogues of biosynthetic intermediates that might lead to "quasi-natural" products (products similar to natural products but not produced under natural conditions). No detectable incorporations of deuterium labeled 1′-methoxytryptophans into phytoalexins or glucobrassicin were detected. l-tryptophan was incorporated in a higher percentage than d-tryptophan into both phytoalexins and phytoanticipins. However, in the case of the phytoalexin rapalexin A, both d- and l-tryptophan were incorporated to the same extent. Furthermore, the transformations of both 1′-methylindolyl-3′-acetaldoxime and 1′-methylindolyl-3′-acetothiohydroxamic acid (quasi-natural products) into 1′-methylglucobrassicin but not into phytoalexins suggested that post-aldoxime enzymes in the biosynthetic pathway of indolyl glucosinolates are not substrate-specific. Hence, it would appear that the 1-methoxy substituent of the indole moiety is introduced downstream from tryptophan and that the post-aldoxime enzymes of the glucosinolate pathway are different from the enzymes of the phytoalexin pathway. A higher substrate specificity of some enzymes of the phytoalexin pathway might explain the relatively lower structural diversity among phytoalexins than among glucosinolates.
- Pedras, M. Soledade C.,Okinyo-Owiti, Denis P.,Thoms, Ken,Adio, Adewale M.
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experimental part
p. 1129 - 1138
(2010/06/21)
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- Reaction of vitamin e compounds with n-nitrosated tryptophan derivatives and its analytical use
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We recently showed that nitrosated tryptophan residues may act as endogenous nitric oxide storage compounds. Here, a novel reaction of nitrosotryptophan derivatives is described, in the form of the release of nitric oxide from N-nitrosotryptophan derivatives initiated either by a-tocopherol or by its water-soluble form trolox. α-Tocopherol and trolox were found to release stoichiometric amounts of nitric oxide from N-acetylN-nitrosotryptophan as well as from the nitrosotryptophan residue in albumin. The reaction proceeds both in water and in lipophilic solution and reconstitutes the indole moiety of the tryptophan molecule quantitatively. During this reaction, α-tocopherol- and trolox-derived phenoxyl-type radicals were identified as intermediates by ESR spectrometry. The chemical mechanism of the NO-releasing process was established. Since S-nitrosothiols donot react under the applied conditions, it is suggested that the trolox-dependent release of nitric oxide may be utilizable for the detection of N-nitrosotryptophan residues in biological samples. Furthermore, as N-nitrosotryptophan derivatives do not undergo spontaneous decay in lipophilic environments, vitamin E may have the so far unrecognized function of preventing the accumulation of N-nitrosotryptophan residues to toxic concentrations in biological systems.
- Mueller, Karsten,Korth, Hans-Gert,De Groot, Herbert,Kirsch, Michael
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p. 7532 - 7542
(2008/03/14)
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- Catecholamine-induced release of nitric oxide from N-nitrosotryptophan derivatives: A non-enzymatic method for catecholamine oxidation
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In recent years, interest in the physiological functions of S-nitrosothiols has strongly increased owing to the potential of these compounds to release nitric oxide. In contrast, little is known about similar functions of N-nitrosated (N-terminal-blocked) tryptophan derivatives, which can be also formed at physiological pH. Utilizing N-acetyl-N-nitrosotryptophan (NANT) and N-nitrosomelatonin (NOMela) as model compounds, we have studied their reaction with catechol and catecholamines such as epinephrine and dopamine. In these reactions, NANT was quantitatively converted to N-acetyltryptophan (NAT), and nitric oxide was identified as a volatile product. During this process, ortho-semiquinone-type radical anions deriving from catechol and dopamine, were detected by ESR spectrometry. The catechol radical concentration was about eight times higher under normoxia than under hypoxia and a similar relationship was found for the decay rates of NANT under these conditions. An epinephrine-derived oxidation product, namely adrenochrome, but not a catechol-derived one, was identified. These observations strongly indicate that N-nitrosotryptophan derivatives transfer their nitroso-function to an oxygen atom of the catecholamines, and that the so-formed intermediary aryl nitrite may decompose homolytically with release of nitric oxide, in addition to a competing hydrolysis reaction to yield nitrite and the corresponding catechol. These conclusions were supported by quantum chemical calculations performed at the CBS-QB3 level of theory. Since nitric oxide is non-enzymatically released from N-nitrosotryptophan derivatives on reaction with catecholamines, there might be a possibility for the development of epinephrine-antagonizing drugs in illnesses like hypertension and pheochromocytoma. The Royal Society of Chemistry 2006.
- Kytzia, Anna,Korth, Hans-Gert,De Groot, Herbert,Kirsch, Michael
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p. 257 - 267
(2007/10/03)
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- Chemical compounds
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Compounds of the general structural formula (I) and use of the compounds and salts and solvates thereof, as therapeutic agents.
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- Fluorescence anisotropy and mobility of dansyl fluorophore in labelled homologous alkanes
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Using the steady-state and time-resolved fluorescence anisotropy, the mobility of 5-(dimethylamino)naphthalene-1-sulfonyl (dansyl) fluorophore in homologous 1-[2-acetamido-3-(1H-indol-3-yl)propanamido[-n-]5-(dimethylamino)naphthalene-1-s ulfonamido]alkanes 1 was studied in binary solvents glycerol-water. Steady-state fluorescence data were evaluated by the generalized Perrin equation and the micro-Brownian motion of dansyl fluorophore was described by means of average characteristics (rotational relaxation times) of the rotational relaxation spectrum. The rotational relaxation time of "fast" motions caused by torsional vibrations of single bonds within the rotational-isomeric states decreases with increasing number of methylene groups in homologous compounds. The rotational relaxation time of "slow" motions due to conformational changes of the chain between the tryptophane and dansyl fluorophore remains at first approximately constant with increasing number of methylene groups but increases considerably for long aliphatic chains. The observed decrease in the rate of conformational changes of a long aliphatic chain is probably due to intramolecular interaction of parts of the methylene chain in a medium with high water content. The values of activation enthalpy ΔH+ and activation entropy ΔS≠ calculated from experimental data corroborate such interpretation. Time-resolved anisotropy of dansyl fluorophore at a particular binary solvent composition confirmed the shape of rotational relaxation spectrum and the measured rotational correlation times have been discussed. The time-dependent decays of anisotropy supported our previous interpretation in terms of intramolecular association of the long aliphatic chain in polar medium.
- Vyprachticky, Drahomir,Pokorna, Veronika,Pecka, Jan,Mikes, Frantisek
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p. 1369 - 1384
(2007/10/03)
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- A general and accurate nmr determination of the enantiomeric purity of α-aminoacids and α-aminoacid derivatives
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Derivatization of α-aminoacids, α-aminoesters and α-aminolactones as N-acetyl derivatives allow the accurate NMR determination of the enantiomeric purity. In these conditions the major coordination site with a chiral shift reagent will correspond to the NMR observation site. Experimental factors leading to the highest ΔΔδ values are ascertained. No straightforward correlation with absolute configurations can be established.
- Calmes, Monique,Daunis, Jacques,Jacquier, Robert,Verducci, Jean
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p. 2285 - 2292
(2007/10/02)
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- Kinetics and Mechanism of the Nitrosation of N-Acetyltryptophan and of the Denitrosation of N-Acetyl-N1-nitrosotryptophan
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Both the formation and the denitrosation of N-acetyl-N1-nitrosotryptophan have been studied kinetically in aqueous solution at 25 deg C at acidities between 1M-HClO4 and pH 4.A value of 850 l mol-1 has been obtained for the equilibrium constant for the formation of N-acetyl-N1-nitrosotryptophan.At acidities (+>) greater than 0.1M the rate constants for both nitrosation and denitrosation increase linearly with the concentration of acid, and the reaction rates are unaffected by the addition of nucleophiles (Br- and SCN-).The results are consistent with a mechanism for nitrosation where the rate-limiting step is the proton transfer from the protonated N-nitroso species to the medium.For denitrosation the corresponding protonation of the nitrosamine is rate-limiting.These conclusions are confirmed by the results obtained when the reactions are carried out in heavy water.However, in the pH range 1-4 the rates of both nitrosation and denitrosation are independent of the acidity of the medium and are again unaffected by the presence of nucleophiles or buffers.It is suggested that in this region nitrosation occurs at C-3.This is followed by deprotonation and an internal NO migration from C to N which is rate-limiting.This mechanism also accounts for earlier results on the denitrosation reaction at even lower acidities (pH 4-7), where acid catalysis and nucleophilic catalysis are found.Results of experiments in heavy water are compatible with this mechanism.
- Castro, Albino,Iglesias, Emilia,Leis, J. Ramon,Pena, M. Elena,Tato, Jose Vazquez,Williams, D. Lyn H.
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p. 1165 - 1168
(2007/10/02)
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- Denitrosation of N-Acetyl-N1-nitrosotryptophan in Acid Solution
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The denitrosation of DL-N-acetyl-N1-nitrosotryptophan has been studied kinetically in water in the acid range 4*10-2 - 1M-H2SO4 and also at lower acidities in buffer solutions pH 2-6.The reaction gave DL-N-acetyltryptophan and nitrous acid quantitatively and was not significantly reversible under these conditions.First-order behaviour was found for both the nitrosamine and acid in the sulphuric acid reactions, and the reaction was also acid-catalysed in the pH region 2-6.The reaction rate constant was unaffected by the addition of N-acetyltryptophan.In 0.04M -H2SO4 the rate constant was unchanged by the addition of bromide ion, thiocyanate ion, iodide ion, and thiourea, and the kinetic solvent isotope effect kH2O/kD2O was 1.3 at 0.7M-H2SO4 and 1.1 at 0.1M-H2SO4.However at pH 6 catalysis was observed by chloride, bromide, thiocyanate, azide, and iodide ion with increasing efficiency along this sequence.As the concentration of the nucleophile was increased the reaction rate constant tended to become independent of the nucleophile concentration.Thus N-acetyl-N1-nitrosotryptophan behaves as a typical nitrosamine at very low acidities around pH 6, whereas at higher acidities it shows a pattern of behaviour reminiscent of that shown by nitrosamides.The pH-rate profile for denitrosation shows clearly that there are two pathways associated with the acid-catalysed reaction, one predominant at around pH 4-7 and the other at acidities greater than pH 1.The former is associated with nucleophilic catalysis and the latter is not.The results are discussed in terms of two possible sites of protonation of the substrate (at O and C-3), and the changing effective rate limiting step, as the nucleophile concentration is changed.N-Acetyl-N1-nitrosotryptophan can be used to nitrosate (or diazotise) other species such as 4-nitroaniline, but only in the absence of a nitrous acid trap, indicating that this nitrosamine is not a direct nitrosating agent towards amines under these conditions.A minor photochemical decomposition pathway has been established for N-acetyl-N1-nitrosotryptophan at pH 6, but it was not examined in detail.
- Meyer, Thomas A.,Williams, D. Lyn H.,Bonnett, Raymond,Ooi, Suan L.
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p. 1383 - 1388
(2007/10/02)
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