Acid–base characterization of 5-hydroxypyrazine-2-carboxylic acid and the role of ionic equilibria in the optimization of some process conditions for its biocatalytic production

This paper describes the use of potentiometric titration to determine the relevant acid–base properties of 5-hydroxypyrazine-2-carboxylic acid (5OH-PYCA), an important intermediate in the production of tuberculostatics. The data obtained were used for calculation of the dissociation constants of 5OH-PYCA. It was found that 5OH-PYCA dissociates in two steps, with the corresponding dissociation constants pK _a1=3.42 and pK _a2=7.96, designating 5OH-PYCA as a medium weak acid (1st step). The distribution diagram of dissociated species and the buffer-strength diagram of 5OH-PYCA provide useful information about its behaviour at different pH. The ionic equilibria data obtained can be used for selection of the optimum pH for biotransformation of pyrazine-2-carboxylic acid (PYCA) and for prediction of pH changes during the biotransformation. These data can also be used for selection of the optimum pH for precipitating 5OH-PYCA in downstream processing. All computations have been optimized by mathematical modelling using Solver.     

A Comparison in the Efficiency of Six Standard 2-Amino-2-Deoxy-Glucosyl Donors for the Synthesis of (2-Deoxy-2-Phthalimido-β-D-Glucopyranosyl) (1→ 4)-β-D-Glucopyranosides.

ABSTRACT

A systematic study is presented for the most common methods used for the preparation of the disaccharide benzyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-(1→'4)-3,6-di-O-benzoyl-2-deoxy-2-phthalimido-β-D-glucopyranoside (9) from “standard 2-amino-2-deoxyglucopyranosyl donors” 1-6 and benzyl 3,6-di-O-benzoyl-2-deoxy-2-phthalimido-β-D-glucopyranoside (7) as an acceptor. It was found that the highest yield was obtained when the trichloroacetimidate derivative 1 was coupled to the 4 position of acceptor 7. In an analogous manner, the disaccharides allyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-(1→'4)-3,6,-di-O-benzoyl-2-deoxy-2-phthalimido-β-D-glucopyranoside (10), benzyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-(1→'4)-3,6-di-O-benzoyl-2-deoxy-2-phthalimido-β-D-galactopyranoside (12), and allyl O-(3,4,6-tri-O-acetyl-2-deoxy-2-phthalimido-β-D-glucopyranosyl)-(1→'3)-4,6-O-benzylidene-2-deoxy-2-phthalimido-β-D-glucopyranoside (14) were prepared.     

Thermodynamics of the Dissociation of Carbonic Acid in Mixed Solvent.4. The System of NaHCO_3-Na_2CO_3-NaCl-Ethanol-Water

Theeffectofethanol-watermixtureontheseconddissociationconstantofcarbonicacidwasofinterestnotonlyforbiologistsbutalsoforchefestsandchemicalengineers,becauseitmayprovideusefulinformationinregardtotheidentificationofthenatureofthesesolute-solventinteractionpatternsinbinarysolventsystem"'.ThispaperreportStheseconddissociationconstantsofcarbonicacid,K,,atfivetemperaturesfrom278.15to318.15Kin5,15,25mass%ethanol-water"dxedsolventsdeterminedfrompreciseelnfmeasurementsincell(A)withoutliquidjunction:Pt…     

A Simple and Efficient New Approach to the Total Synthesis of (±)-4-Amino-3-(4-Chlorophenyl)-Butyric Acid (BACLOFEN)

Based on the utilization of a [2+2] cycloaddition reaction between dichloroketene and an appropriated olefin as a key step, we describe a new and simple four step approach to the total synthesis of (±)-4-amino-3-(4-chlorophenyl)-butyric acid (BACLOFEN), a selective GABA_B agonist used as antispastic agent     

A new modification of the Friedländer synthesis. A simple route to 2-aminoquinoline-3-carboxylic acid and its derivatives

A new version of the Friedländer synthesis of 2-aminoquinoline-3-carboxylic acid and its derivatives from stable 2-tosylaminobenzaldehyde or its morpholinal was proposed.     

Preparation of AgBiVMoO/γ-Al_2O_3 Catalysts for the Partial Oxidation of Propane to Acrylic Acid by the Mixed Sol Method

A novel mixed sol method was developed for the preparation of supported catalysts. Analyses by means of XRD and BET show that a 40%AgBiVMoO/γ-Al2O3 catalyst prepared by this method possessed high specific surface area and high dispersion of the active phase. As a result, high acrylic acid selectivity of 8.5% was obtained when the catalyst was used in the reaction of propane partial oxidation to acrylic acid in a fixed-bed reactor.     

New method for studying the reactivities of α-diazo imines. Investigation of the cyclization of N-substituted 2-diazoacetamidines to 1,2,3-triazoles

N-Substituted diazoacetamidines were generated in the reaction of N-substituted acetamidines with benzenesulfonyl azide. It is shown that their cyclization to isomeric 1,2,3-triazoles characterizes the reactivities of -diazo imines. The synthesis of 5-amino-1,2,3-triazole derivatives was accomplished, and their ¹H, ¹³C, and ¹⁵N NMR spectra were studied.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 775–782, June, 1991.     

γ-Al2O3-Supported 12-Tungstosilicic Acid as an Efficient Heterogeneous Catalyst for the Synthesis of α-Aminonitrile

The multicomponent Strecker reaction using trimethylsilyle cyanide was performed in very short reaction times, and α-aminonitriles were prepared in excellent yields in the presence of a catalytic amount of alumina-supported tungstosilicic acid.     

Stark spectrum simulation for X2Y4 molecules: application to the ν12 band of ethylene in a high-silica zeolite

The influence of an electric field of silicalite-1-zeolite on the FTIR vibrational absorption spectrum of ethylene has been simulated and compared to experimental spectra. The presence of silicalite-1 produces a global shift and a change of the structure of vibrational bands. To explain the global shift of the ν(12) band (CH(2) scissor mode) and therefore to estimate an effective average field produced by silicalite-1, Stark calculations were performed. These calculations were based on a tensorial formalism implemented in the D(2h)TDS-ST package [M. Sanzharov, M. Rotger, C. Wenger, M. Lo?te, V. Boudon, and A. Rouzée, J. Quant. Spectrosc. Radiat. Transf. 112, 41 (2011)]. The value of the field obtained using tensorial formalism (8-11 GV/m) is compared with values obtained using ab initio calculations. A theory of the molecular alignment in the electric field using tensorial formalism is also developed to model the interaction of ethylene in contact with a zeolite environment.     

Effect of CeO_2 Promoter on the Performance of Catalyst for CH_4, CO_2with O_2 to Synthesis Gas

Inrecentyears,thereactionofmethane,carbondioxidewithoxygentosynthesisgashasbeenreceivingmore.attentionfromthevieWPointofPrpservingglobalenvironment,becauseCH#andCO,areofgreenhousegasesandtheircontributiontoglobalwarmingisverylargeowingtotheirhugeamountreleasedintheatmosphere'.Inaddition,therearetwoadvantagesinthisprocessobviously,bychangingtheratiooffeed,itcanachievethermalneutralizingandtheCO/H,ratiocanlbebovariedintherangeof0.5~ltofitdifferentindustrialrequirement.Therearehardlyanypapers…     

Study on the Stereoselective Synthesis of Carbapenem Sidechain (2S,4S)-4-Acetylsulphanyl-2-[(S)-1-phenylethylcarbamoyl]-pyrrolidine-1-carboxylic Acid 4-Nitrobenzyl Ester

A stereoselective and economic synthesis of the carbapenem sidechain (2S, 4S)-4-ace-tylsulphanyl-2-[(S)1-phenylethyl-carbamoyl] pyrrolidine-1-carboxylic acid 4-nitrobenzylester was developed. Due to the effect of spatial hindrance, only the (2S,4S) diastereomer 3 wasobtained by coupling 1 and the inexpensive racemic 2 catalyzed by EEDQ.     

Single-entity Electrochemistry Unveils Dynamic Transformation during Tandem Catalysis of Cu2O and Co3O4 for Converting NO3− to NH3

Electrochemically converting nitrate to ammonia is an essential and sustainable approach to restoring the globally perturbed nitrogen cycle. The rational design of catalysts for the nitrate reduction reaction (NO₃RR) based on a detailed understanding of the reaction mechanism is of high significance. We report a Cu₂O+Co₃O₄ tandem catalyst which enhances the NH₃ production rate by ≈2.7-fold compared to Co₃O₄ and ≈7.5-fold compared with Cu₂O, respectively, however, most importantly, we precisely place single Cu₂O and Co₃O₄ cube-shaped nanoparticles individually and together on carbon nanoelectrodes provide insight into the mechanism of the tandem catalysis. The structural and phase evolution of the individual Cu₂O+Co₃O₄ nanocubes during NO₃RR is unveiled using identical location transmission electron microscopy. Combining single-entity electrochemistry with precise nano-placement sheds light on the dynamic transformation of single catalyst particles during tandem catalysis in a direct way.     

Synthesis of a New Polymer-supported Reagent──Poly{[4- hydroxy(tosyloxy)iodo]styrene} and Its Application to the Synthesis of 2-Amino-4-arylthiazoles

Ｉｔｉｓｗｅｌｌｋｎｏｗｎｔｈａｔｐｏｌｙｍｅｒ ｓｕｐｐｏｒｔｅｄｒｅａｇｅｎｔｓｈａｖｅｔｈｅａｄｖａｎｔａｇｅｏｆａｌｌｏｗｉｎｇｔｈｅａｐｐｌｉｃａｔｉｏｎｏｆａｌａｒｇｅｒｅｘｃｅｓｓｏｆｔｈｅｒｅａｇｅｎｔｗｉｔｈｏｕｔａｄｄｉｔｉｏｎａｌｐｕｒｉｆｉｃａｔｉｏｎｓｔｅｐｓ .Ｔｈｅｍｏｓｔｉｍｐｏｒｔａｎｔｐｏｉｎｔｉｓｔｈａｔｔｈｅｐｏｌｙｍｅｒ ｓｕｐｐｏｒｔｅｄｒｅａｇｅｎｔｓｃｏｕｌｄｂｅｅａｓｉｌｙｒｅｇｅｎｅｒａｔｅｄａｎｄｒｅｕｓｅｄ ,1ｗｈｉｃｈｍｅｅｔｓｔｈｅｒｅｑｕ…     

Methods for the Synthesis of 3,4-2H-Dihydropyrroles (Δ1-Pyrrolines) and Their Chemical Transformations. (Review)

Published data on the synthesis and chemical transformations of 3,4-2H-dihydropyrroles (¹-pyrrolines) are analyzed and reviewed for the first time.     

Buffers for the Physiological pH Range: Thermodynamics of the Second Dissociation of N-(2-Hydroxyethyl)piperazine-N′-2-hydroxypropanesulfonic Acid From 5 to 55°C

The second acidic dissociation constants pK ₂ of the ampholyte N-(2-hydroxyethyl) piperazine-N-2-hydroxypropanesulfonic acid (HEPPSO) have been determined at seven temperatures from 5 to 55°C from emf measurements utilizing hydrogen and silver–silver chloride cells without liquid junction. The thermodynamic quantities, G°, H°,S°, and C _p ^o have been calculated from the temperature coefficient of pK ₂. At 25°C, the pK ₂ = 8.042 and at 37°C, pK ₂ = 7.876; hence, buffer solutions of HEPPSO and NaHEPPSOate are important for pH control in the region close to that of clinical fluids (blood serum). Conventional pH values from 5 to 55°C as well as those obtained from liquid junction correction at 25 and 37°C have been reported for three buffer solutions with the compositions (molality scale): (1) equimolal mixture of HEPPSO (0.04 m) + NaHEPPSOate (0.04 m) + NaCl (0.12 m); (2) HEPPSO (0.08 m) + NaHEPPSOate (0.08 m); and (3) HEPPSO (0.08 m) + NaHEPPSOate (0.08 m) + NaCl (0.08 m).     

Identification of Amino Acid Residues Responsible for the Binding to Anti-FLAG™ M2 Antibody Using a Phage Display Combinatorial Peptide Library

FLAG, a short hydrophilic peptide consisting of eight amino acids (DYKDDDDK), has been widely used as a fusion tag for the purification and detection of a wide variety of recombinant proteins. One of the monoclonal antibodies against this peptide, anti-FLAG M2, recognises a FLAG peptide sequence at the N terminus, Met-N terminus, C terminus, or internal site of a fusion protein and has been extremely useful for the detection, identification, and purification of recombinant proteins. Nevertheless, detailed binding specificity of anti-FLAG M2 has yet to be determined. In the current study, a phage display combinatorial peptide library was used to determine that the motif DYKxxD encompasses the critical amino acid residues responsible for the binding of FLAG peptide to this antibody. This study demonstrates the utility of phage display technology and helps to elucidate the mode of action of this detection system.     

A Plasma-Activated Ni/α-Al2O3 Catalyst for the Conversion of CH4 to Syngas

Nickel-based catalysts supported on -Al₂O₃ for the partial oxidationof methane were activated by a glow discharge plasma technique. Theactivating process was simple, quick, audio-visual, and easy to control. Theactivity and stability of the activated catalyst were higher than those ofconventional catalysts. The methane conversion of 98.2% and selectivity of97.3% to hydrogen and 96.5% to carbon monoxide were obtained at850°C. The catalyst could maintain its activity over 15 hr. According tothe results of X-ray diffraction (XRD) and temperature-programmed reduction(TPR), the component of crystal phase and the reducibility of the activatedcatalyst were significantly different from those of conventionalcatalysts.     

Overexpression of Δ12-Fatty Acid Desaturase in the Oleaginous Yeast <Emphasis Type="Italic">Rhodosporidium toruloides</Emphasis> for Production of Linoleic Acid-Rich Lipids

Under nutrient-limited conditions, the red yeast Rhodosporidium toruloides can accumulate neutral lipids, of which the compositional fatty acids are mainly saturated and mono-unsaturated ones with 16 or 18 carbon atoms. To improve the linoleic acid content in the lipids, we enabled galactose-inducible expression of the gene encoding Δ12-fatty acid desaturase (FADS) from Mortierella alpina or Fusarium verticillioides by integration of the corresponding expression cassettes into the genome of R. toruloides haploid and diploid strains. The relative linoleic acid content increased up to fivefold and the final linoleic acid titer reached 1.3 g/L under flask culture conditions. Our results suggested that R. toruloides may be further explored as cell factory for production of high-valued lipids and other fatty acid derivatives as bio-based chemicals and fuels.