Synthesis of <Emphasis Type="Italic">ortho</Emphasis>-carboranyl derivatives of (<Emphasis Type="Italic">S</Emphasis>)-asparagine and (<Emphasis Type="Italic">S</Emphasis>)-glutamine

(S)-Asparagine and (S)-glutamine ortho-carboranyl derivatives with free amino and carboxy groups in the α-position were synthesized. By an example of N ^γ-(1,2-dicarba-closo-dodecarboran-3-yl)-(S)-glutamine it was demonstrated that the developed synthetic approach carboranyl derivatives of amino acids allowed the preparation of optically pure isomers.     

Effect of the structure of the <Emphasis Type="Italic">ortho</Emphasis>, <Emphasis Type="Italic">meta</Emphasis>, and <Emphasis Type="Italic">para</Emphasis> isomers of perhydroterphenyl on their reactivity in heterogeneous catalytic dehydrogenation

The kinetics of the dehydrogenation of the individual ortho, meta, and para isomers of perhydroterphenyl and their mixtures over a (3 wt % Pt)/C catalyst has been investigated in a flow reactor at 280–340°C. The rate of the isomerization of the stereoisomers of the initial substrate (perhydroterphenyl) and terphenyl dehydrogenation products has an effect on the hydrogen release kinetics. The highest reactivity in isomerization is shown by the ortho isomer. The largest amount of hydrogen (7.0 wt %) is released in the dehy-drogenation of perhydro-meta-terphenyl and perhydro-para-terphenyl, whose conversion at 320°C is 96%.     

Crystal structure of <Emphasis Type="Italic">ortho</Emphasis>-toluidinium hexafluorosilicate

The structure of the complex (o-CH₃C₆H₄NH₃)₂SiF₆ was determined by X-ray diffraction. In the ionic structure of the complex, the SiF ₆ ^2? anions (Si-F, 1.595(9)-1.683(17)Å) and the o-CH₃C₆H₄NH ₃ ⁺ cations are combined by NH?F hydrogen bonds (N?F 2.757(10)-3.25(2) Å). The components of the structure are combined into a layer whose central part is formed by the SiF ₆ ^2? anions and the outer hydrophobic surfaces are formed by the aromatic rings of the cations.     

<Emphasis Type="Italic">Z</Emphasis>-and <Emphasis Type="Italic">E</Emphasis>-conformers of <Emphasis Type="Italic">N</Emphasis>-chloroacetylcytisine

N-Chloroacetylcytisine was synthesized by acylation of (–)-cytisine. Stable Z- and E-conformers with respect to rotational isomerism around the N-12–CO bond were found in PMR spectra at room temperature. The point at which PMR resonances of the Z- and E-conformers coalesced upon heating was measured. The transition barrier between the conformers was estimated.     

Excess enthalpies of binary mixtures of <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-structural isomers

The excess molar enthalpies of 8 binary mixtures for the o-, m-, and p-isomers of fluoroiodobenzene, fluoromethoxybenzene, bromofluorobenzene, chlorofluoro-benzene, difluorobenzene, fluoromethylbenzene, fluoronitrobenzene, and aminofluoro-benzene were measured at 298.15 K. The changes of the measured enthalpies were very small. The experimental results revealed that the isomers containing two electron-acceptor groups showed the most positive excess enthalpy change, while isomers containing both one electron donor and one electron acceptor group, such as aminofluorobenzene, showed more stable and always the most negative results.     

Photolysis of <Emphasis Type="Italic">ortho</Emphasis>-azidophenol in various solvents

The photolysis of ortho-azidophenol in water, ethanol, acetonitrile, chloroform, and benzene was studied by IR and electronic spectroscopy and thin-layer chromatography. It was found that an equilibrium between ortho-azidophenol and its quinonoid form occurred in benzene. In the photolysis of ortho-azidophenol in benzene, intramolecular hydrogen bonding facilitates the degradation of the azido group through the mechanism of formation of intermediate triazene structures. In the other solvents, which exclude intramolecular hydrogen bonding, the nitrene mechanism of photolysis yielding ortho-aminophenol, ortho-iminoquinone, and an azo compound is operative. The rate of formation of photolysis products depends on the nature of the solvent.     

Geminal acylnitrostyrenes in the reaction with <Emphasis Type="Italic">ortho</Emphasis>-aminothiophenol

The synthesis of previously unknown 2,3- and 2,5-dihydro-1,5-benzothiazepines sontaining nitro group was performed by the easy sondensation of geminal acylnitrostyrenes with the o-aminothiophenol. The structure of the obtained sompounds was studied by physicochemical methods. By X-ray diffraction analysis the geometry and structural parameters of 4-methyl-3-nitro-2-phenyl-2,3-dihydro-1,5-benzothiazepine were determined.     

Synthesis and deborination of polyhalo-substituted <Emphasis Type="Italic">ortho</Emphasis>-carboranes

Tetraiodo-1,2-dicarba-closo-dodecaborane and 9-bromo-8,10,12-triiodo-1,2-dicarba-closo-dodecaborane were synthesized by oxidative iodination of 1,2-dicarba-closo-dodecaborane and 9-bromo-1,2-dicarba-closo-dodecaborane, respectively, in AcOH using a mixture of nitric and sulfuric acid as an oxidant of iodine. The intermediates in the ortho-carborane iodination were identified. By the action of elemental bromine on 9-iodo-1,2-dicarba-closo-dodecaborane in the presence of aluminum chloride catalyst 9-iodo-8,10,12-tribromo-1,2-dicarba-closo-dodecaborane was obtained. Deborination of the synthesized substances with an alcohol solution of KOH led to formation of 1,5,6,10-tetraiodo-5-bromo-1,6,10-triiodo- and 5-iodo-1,6,10-tribromo-7,8-dicarbaundecaborates methylammonium salts.     

Excess enthalpies of binary mixtures of <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, <Emphasis Type="Italic">para</Emphasis>-structural isomers containing aliphatic group

To obtain further systematic information for the isomer systems, the excess molar enthalpies for binary (o + m), (o + p), (m + p)-isomers of methoxymethylbenzene, ethylmethylbenzene, diethylbenzene, chloromethylbenzene, tolunitrile and fluorobenzonitrile, tolylacetonitrile were measured at 298.15 K. In this article, the results are discussed and compared with those of previous works. The excess enthalpies of binary systems in different solid and liquid states were measured when the pure component of o-/m-tolunitrile, fluorobenzonitrile was titrated into the prior (o + p) or (m + p) mixtures. A series calculation for the interaction energies (IE) between the isomers was carried out for the pair molecules by ab initio MO of Gaussian 09. Correlations between the excess enthalpies at a molar fraction of x = 0.5 and the intermolecular energy are discussed.     

New Photochromic Spiropyrans with <Emphasis Type="Italic">ortho</Emphasis>-Hydroxyaldimine Substituent

A series of new spiropyrans of indoline series with ortho-hydroxyaldimine substituent has been synthesized, their structure and photochromic properties have been studied. The structure of the obtained compounds was confirmed by the data of 1H NMR and IR spectroscopy and elemental analysis. Photochromic properties of the prepared compounds have been studied. The introduction of ortho-hydroxy group into aldimine fragment of molecule (in the 6 position of the 2H-chromene fragment) has increased the lifetime of merocyanine isomer by 40 times as compared with amino-substituted spiropyran.     

Formation of solvate structures by the <Emphasis Type="Italic">ortho</Emphasis>-, <Emphasis Type="Italic">meta</Emphasis>-, and <Emphasis Type="Italic">para</Emphasis>-isomers of hydroxybenzoic acid in supercritical fluid

The solvate structures formed by the ortho-, meta-, and para-isomers of hydroxybenzoic acid (o-HBA, m-HBA, and p-HBA) with a polar co-solvent (methanol at a concentration of 0.030 and 0.035 mole fractions) in supercritical carbon dioxide at a constant density of 0.7 g/cm³ and temperatures of 318 and 328 K have been studied by the classic molecular dynamics. It has been determined that a stable hydrogen-bonded complex with the co-solvent forms via the hydrogen of the carboxyl group for all isomers. The probability of this complex existence is high at all temperatures and concentrations. In the o-HBA molecule, the other functional groups are engaged in the intramolecular hydrogen bond, but not involved in interactions with methanol. It has been found that m-HBA and p-HBA can be involved in hydrogen bonds with methanol via hydroxyl hydrogen and oxygen atoms; they are characterized by the presence of one more co-solvent molecule (rarely, two molecules) in their solvation shell and intermittent formations/breakages of hydrogen bonds via other functional groups. These bonds are far less stable, and their formation is sensitive to change of temperature and co-solvent concentration. It has been concluded that the degree of selective solvation of m-HBA and p-HBA by co-solvent molecules is approximately the same, but the rate of structural rearrangements in the nearest environment of m-HBA is higher than that of p-HBA.     

Molecular properties of the copolymers of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride and maleic acid

The hydrodynamic and conformational properties of molecules of poly(N,N-diallyl-N,N-dimethylammonium chloride) and N,N-diallyl-N,N-dimethylammonium chloride-maleic acid copolymers of different compositions in solutions with various ionic-strength and pH values, as well as of the polyelectrolyte complex based on the copolymer with dodecyl sulfate anions in chloroform, are studied. For poly(N,N-diallyl-N,N-dimethylammonium chloride) molecules in a 1 M NaCl solution, the Kuhn segment length and the hydrodynamic diameter of the chain are estimated as A = 3.9 nm and d = 0.48 nm, respectively. In acidic solutions with pH 3.5, the copolymers demonstrate behavior typical for polyelectrolytes. In an alkaline solution with pH 13, when 1 M NaCl is added to the solution of the copolymer containing 29 mol % maleic acid units, there is an antipolyelectrolyte effect that manifests itself as an increase in the intrinsic viscosity of the copolymer and in the hydrodynamic radius of its molecules. It is found that an increase in the fraction of maleic acid units in the copolymer from 12 to 42 mol % brings about a reduction in the equilibrium rigidity of its macromolecules from 4.1 to 2.2 nm. The equilibrium rigidity of polyelectrolyte-complex molecules is higher than that of initial copolymer molecules owing to steric interactions arising between the aliphatic chains of dodecyl sulfate anions. In an electric field, the molecules of the complex are oriented owing to the induced dipole moment resulting from the displacement of dodecyl sulfate anions along the chain contour.     

Supramolecular synthons in fluorinated and nitrogen-rich <Emphasis Type="Italic">ortho</Emphasis>-diaminotriazoles

5-Substituted 3,4-diamino-1,2,4-triazoles can be obtained in moderate to good yields in a one-pot reaction starting from a carboxylic acid and dimethylaminoguanidine monohydrochloride in polyphosphoric acid (PPA) at 120 °C. Several triazoles and bistriazoles have been prepared in this way, with substituents ranging from alkyl to aryl, including perfluoroaryl or perfluoroalkyl substituents. The crystal structure analysis of three perfluorinated diaminotriazoles has evidenced a most stable R₂² (8) R_{2}^{2} (8) H bonding synthon, involving the amino CNH₂ donor and the adjacent nitrogen ring acceptor; additionally, two new synthons consisting of chains of rings have been identified. The relevance of the short F⋯F intermolecular contacts found in the structures is also discussed.     

Copolymer of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-diallyl-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimethylammonium chloride with maleic acid as drug carrier

A copolymer of N,N-diallyl-N,N-dimethylammonium chloride with maleic acid of constant composition was prepared under the conditions of radical initiation. The possibility of the functionalization of the copolymer with drugs containing amino groups by polymer-analogous transformations was examined. Conditions were found for preparing conjugates of the copolymer with isoniazid. The structures and the quantitative compositions of the conjugates were determined by ¹³С NMR spectroscopy, and the possibility of preparing conjugates with controlled drug content was demonstrated.     

Analysis of <Emphasis Type="Italic">Escherichia coli</Emphasis> nicotinate mononucleotide adenylyltransferase mutants <Emphasis Type="Italic">in vivo</Emphasis> and <Emphasis Type="Italic">in vitro</Emphasis>

Background  

Adenylation of nicotinate mononucleotide to nicotinate adenine dinucleotide is the penultimate step in NAD⁺ synthesis. In Escherichia coli, the enzyme nicotinate mononucleotide adenylyltransferase is encoded by the nadD gene. We have earlier made an initial characterization in vivo of two mutant enzymes, NadD72 and NadD74. Strains with either mutation have decreased intracellular levels of NAD⁺, especially for one of the alleles, nadD72.     

Spectral and quantum-chemical investigation of <Emphasis Type="Italic">ortho</Emphasis>- and <Emphasis Type="Italic">peri</Emphasis>-hydroxy-substituted mono- and diformyl derivatives of 1,5-naphthalenediol

Spectral and quantum-chemical investigation of ortho- and peri-hydroxy-substituted aldehydes, 1,5-naphthalenediol derivatives, was carried out. An unusual spin-spin coupling through an intramolecular hydrogen bond was discovered in the molecule of 1,5-dihydroxynaphthalene-4,8-dicarbaldehyde. It was shown that this dialdehyde is involved into the ring-chain tautomerism. The position of this equilibrium was examined depending on the temperature and the solvent polarity. The effect of the solvent polarity on the benzoid-quinoid tautomerism in the dihydroxynaphthalene-2,6-dicarbaldehyde was established. By the method of quantum-chemical calculations the relative energy stability and conformational structure of dialdehydes were revealed.     

Robust Parameter Identification to Perform the Modeling of <Emphasis Type="Italic">pta</Emphasis> and <Emphasis Type="Italic">poxB</Emphasis> Genes Deletion Effect on <Emphasis Type="Italic">Escherichia Coli</Emphasis>

The aim of this study was to design a robust parameter identification algorithm to characterize the effect of gene deletion on Escherichia coli (E. coli) MG1655. Two genes (pta and poxB) in the competitive pathways were deleted from this microorganism to inhibit pyruvate consumption. This condition deviated the E. coli metabolism toward the Krebs cycle. As a consequence, the biomass, substrate (glucose), lactic, and acetate acids as well as ethanol concentrations were modified. A hybrid model was proposed to consider the effect of gene deletion on the metabolism of E. coli. The model parameters were estimated by the application of a least mean square method based on the instrument variable technique. To evaluate the parametric identifier method, a set of robust exact differentiators, based on the super-twisting algorithm, was implemented. The hybrid model was successfully characterized by the parameters obtained from experimental information of E. coli MG1655. The significant difference between parameters obtained with wild-type strain and the modified (with deleted genes) justifies the application of the parametric identification algorithm. This characterization can be used to optimize the production of different byproducts of commercial interest.     

Conformations and properties of <Emphasis Type="Italic">O</Emphasis>-Alkyl-<Emphasis Type="Italic">S</Emphasis>-(2-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dialkylamino)-ethylmethylthiophosphonates

Conformers of the biologically active compounds CH₃P(O)(OR)(SCH₂CH₂NR ₂ ^′ ), where (I) R = i-C₄H₉, R′ = C₂H₅ and (II) R = C₂H₅, R′ = i-C₃H₇, are calculated within the AM1 level of theory. The elongated and twisted forms with maximum and minimum distances between a nitrogen atom and those of a phosphorus tetrahedron, respectively, and bearing a syn and anti oriented alkoxy group relative to a phosphoryl oxygen, are studied. It is found that the differences between the energy, electronic, and geometric parameters of these forms are apparent in differences between their properties, e.g., the ability to participate in complexation and protonation, reactions that to some extent simulate the interaction between a substance and a biological object.     

Synthesis of 6-methyl-8<Emphasis Type="Italic">H</Emphasis>-dibenzo[<Emphasis Type="Italic">a</Emphasis>,<Emphasis Type="Italic">g</Emphasis>]quinolizin-8-imines <Emphasis Type="Italic">via Reissert</Emphasis> compounds

Alkylation of Reissert compounds derived from 3-methylisoquinolines with several 2-cyanobenzylbromides followed by hydrolytic cleavage provided the corresponding 1-benzyl-3-methylisoquinolines. Treatment of the latter with methylmagnesiumiodide caused cyclization to the title compounds rather than formation of 2-acetylbenzylisoquinolines.