<Emphasis Type="Italic">N</Emphasis>′-tetrazolylmethoxyl derivatives of <Emphasis Type="Italic">N</Emphasis>-methyldiazene <Emphasis Type="Italic">N</Emphasis>-oxides

A preparation method was developed for previously unknown tetrazole derivatives containing in the 1, 2, and/or 5 positions of the tetrazole ring N-methyldiazene-N-oxide-N′-oxymethyl groups.     

Recognition of <Emphasis Type="Italic">R</Emphasis>- and <Emphasis Type="Italic">S</Emphasis>-Isomers of α-Alanine by Chiral Nanotubes

DFT PBE/3ζ study of relative stability of the R- and S-isomers of α-alanine in open carbon nanotubes with chirality indices (5,5), P,M-(5,1) and P,M-(5,2) has shown that the encapsulated molecule of the amino acid notably changes its geometrical and electronic characteristics. Besides, for the clusters α-alanine@nano (5,2) the most stable are practically degenerate in energy adducts S-alanine@P-(5,2) and R-alanine@М-(5,2). All this indicates the ability of chiral nanotubes to recognize encapsulated molecules of the R- and S-isomers.     

10<Emphasis Type="Italic">α</Emphasis>-Hydroxy-<Emphasis Type="Italic">β</Emphasis>-isomorphine,a by-product of the synthesis of 10<Emphasis Type="Italic">α</Emphasis>-hydroxymorphine

Abstract  A new compound was isolated from the reaction mixture after O-demethylation of 6-O-acetyl-10α-acetoxycodeine with boron tribromide. The structure of this compound, 10α-hydroxy-β-isomorphine, was elucidated by spectral data, and its spatial arrangement was deduced from an NOE experiment. Capillary zone electrophoresis was used for separation of morphine and its 10-hydroxy analogues. Graphical abstract        

Synthesis of <Emphasis Type="Italic">α</Emphasis>-chloropyridine derivatives of <Emphasis Type="Italic">γ</Emphasis>-aminobutyric acid

The sodium salt of N-(6-chloronicotinoyl)-γ-aminobutyric acid, a structural analog of the known nootropic and vasidilating drug picamilon, was synthesized via Schotten–Baumann acylation of γ-aminobutyric acid with 6-chloronicotinoyl chloride and subsequent neutralization of the N-(6-chloronicotinoyl)-γ-aminobutyric acid that was obtained in >60% yield.     

An efficient synthesis of <Emphasis Type="Italic">β</Emphasis>-methoxycarbonyl-<Emphasis Type="Italic">γ</Emphasis>-butyrolactones

β-Methoxycarbonyl-γ-butyrolactones bearing a γ-aromatic substituent were prepared via copper-catalyzed reductive aldol addition/lactonization domino reactions of ketones with α,β-unsaturated dicarboxylate esters and a silane under ambient temperature. The reaction has advantage of using readily available reagents, mild conditions and high efficiency.     

Thermophysical properties of <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>-dimеthylacetamide mixtures with <Emphasis Type="Italic">n</Emphasis>-butanol

The refraction, dielectric, viscosity, density, data of the binary mixtures of N,N-dimethylacetamide (DMA) with n-butanol at 308.15 and 313.15 K. The measured parameters used to obtain derived properties like Bruggeman factor, molar refraction and excess static dielectric constant, excess inverse relaxation time, excess molar volume and excess viscosity, excess molar refraction. The variation in magnitude with composition and temperature of these quantities has been used to discuss the type, strength and nature of binary interactions. Results confirm that there are strong hydrogen-bond interactions between unlike molecules of DMA+ n-butanol mixtures and that 1: 1 complexes are formed and strength of intermolecular interaction increases with temperature.     

Specific features of reversible <Emphasis Type="Italic">E</Emphasis>—<Emphasis Type="Italic">Z</Emphasis>-photoisomerization of crown-containing 4-styrylpyridine complexes with various cations

The reversible photochemical E—Z-isomerization of crown-containing 4-styrylpyridine was studied. The reaction was carried out in the presence of alkaline-earth metals capable of forming complexes with the crown-ether fragment and heavy metal perchlorates (Hg²⁺, Cd²⁺) that are able to coordinate the nitrogen atom of the heterocyclic residue. The influence of complex formation on the E—Z-photoisomerization was determined by electronic spectroscopy and ¹H NMR spectroscopy. The studies performed confirm that the E—Z-photoisomerization can be controlled using supramolecular complex formation.     

Study of<Emphasis Type="Italic"> β</Emphasis>–<Emphasis Type="Italic">α</Emphasis> recrystallization of the polypropylene

The crystalline modifications and of polypropylene (PP) were studied by using polarized light microscopy (PLM), wide-angle X-ray diffraction (WAXD), and differential scanning calorimetry (DSC). Typically crystals surrounded by spherulites were observed at low temperature. With increasing temperature the crystals melted and a new crystal appeared. More interestingly, the melting temperature of the new crystal was about 5 ° higher than that of spherulites originally present in the sample formed isothermally. It was assumed that this new crystal was the recrystalline crystal. This assumption was supported by the DSC results. Furthermore, the crystallization kinetics of the PP used was studied on the basis of the traditional Avrami analysis. As a result, the Avrami exponents of crystallization temperature from 120 to 130 °C ranged between 4.21 and 3.60, indicating that the crystallization mechanism of PP order melt was spherulitic growth and random nucleation.     

Spectroscopic and electrical characterization of <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">γ</Emphasis>-bisdiphenylene-<Emphasis Type="Italic">β</Emphasis>-phenylallyl radical as an organic semiconductor

The semiconductor properties of the earliest known stable radical, α,γ-bisdiphenylene-β-phenylallyl radical (Koelsch radical, 1^?) were assessed using spectroscopic and electrical techniques. This radical undergoes reversible redox processes, and it has low redox potentials. In addition, 1^? possesses long wavelength absorption bands, owing to the existence of a singly-occupied molecular orbital whose energy level lies between those of the HOMO and LUMO. A spin-coated thin-film of 1^? displays photocurrent and an electron mobility of 6.3 × 10^?7 cm² V^?1 s^?1 on a trially-fabricated organic field effect transistor.     

Crystal and molecular structure of (±)-2-[(1<Emphasis Type="Italic">S</Emphasis>,3<Emphasis Type="Italic">S</Emphasis>)-3-acetyl-2,2-dimethylcyclobutyl]-N-(<Emphasis Type="Italic">p</Emphasis>-tolyl)acetamide

The structure of (±)-2-[(1S,3S)-3-acetyl-2,2-dimethylcyclobutyl]-N-(p-tolyl)acetamide has been determined by single crystal X-ray diffraction analysis. The crystal belongs to triclinic system, space group P-1, a = 8.8700(18) Å, b = 10.331(2) Å, c = 10.363(2) Å, α = 71.11(3)°, β = 65.06(3)°, γ = 72.18(3)°, V = 798.6(3) ų, Z = 2, formula unit C₁₇H₂₃NO₂. The title compound has a fragment of 2,2-dimethylcyclo-butane and its conformation represents semi-chair. The intermolecular hydrogen bonds N-H...O and C-H...O are revealed.     

Expression of a Glucose-tolerant β-glucosidase from <Emphasis Type="Italic">Humicola grisea</Emphasis> var. <Emphasis Type="Italic">thermoidea</Emphasis> in <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis>

A β-glucosidase gene (bgl4) from Humicola grisea var thermoidea was successfully expressed in Saccharomyces cerevisiae. The recombinant protein (BGL4 ^Sc ) was initially detected associated with yeast cells and later in the culture medium. BGL4 ^Sc showed optimal pH and temperature of 6.0 and 40 °C, respectively, and an apparent molecular mass of 57 kDa. The enzyme showed activity against cellobiose and synthetic substrates, and was inhibited more than 80% by Fe²⁺, Cu²⁺, Zn²⁺, and Al³⁺. Using p-nitrophenyl-β-d-glucopyranoside (pNPG) as substrate, BGL4 ^Sc presented a V _max of 6.72 μmol min⁻¹ mg total protein⁻¹ and a K _m of 0.16 mM under optimal conditions. Most important, BGL4 ^Sc is resistant to inhibition by glucose and the calculated K _i value for this sugar is 70 mM. This feature prompts BLG4 ^Sc as an ideal enzyme to be used in the saccharification process of lignocellulosic materials for ethanol production.     

Complex formation of magnesium and calcium ions with trimethylenediamine-<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>’,<Emphasis Type="Italic">N</Emphasis>’-tetraacetic acid

Stability constants and heat effects of the formation reactions of magnesium and calcium trimethylenediaminetetraacetates at 298.15 K and ionic strength of 0.1, 0.5, and 1.0 (mol/L KNO₃) have been determined by means of potentiometry and calorimetry. Standard thermodynamic parameters (log K⁰, Δ_rG⁰, Δ_rH⁰, and Δ_rS⁰) of the studied equilibriums have been determined.     

Theoretical and experimental NMR studies of the Swern oxidation of methyl 6<Emphasis Type="Italic">α</Emphasis>,7<Emphasis Type="Italic">β</Emphasis>-dihydroxyvouacapan-17<Emphasis Type="Italic">β</Emphasis>-oate

This work describes the synthesis of new derivatives of 6α,7β-dihydroxyvouacapan-17β-oic acid (1) employing the Swern method for the oxidation of C-6 and C-7 of methyl 6α,7β-di-hydroxyvouacapan-17β-oate (2) and the formation of methyl 6,7-dioxovouacapan-17β-oate (3). NMR structural studies associated with theoretical calculations of reaction intermediates and products are also reported. The mixture of methyl 7β-hydroxy-6-oxovouacapan-17β-oate (4; 21%) and methyl 6α-hydroxy-7-oxovouacapan-17β-oate (5; 79%) was the product from the first step of the oxidation of 2. The lower energy of 5, calculated by HF/6-31G* and DFT/BLYP/6-31G* methods, reinforces the thermodynamic control proposed for the reaction. After further Swern oxidation of the mixture of 4 and 5, the isomeric form methyl 6-hydroxy-7-oxovouacap-5-en-17β-oate (6) was obtained. Theoretical calculations indicate a lower energy for the mono-enol 6 than the 1,2-diketo 3 and the other mono-enol methyl 7-hydroxy-6-oxovouacap-7-en-17β-oate (7).     

Influence of the force interaction on accumulation of macroscopic correlations in elementary reaction <Emphasis Type="Italic">A</Emphasis> + <Emphasis Type="Italic">B</Emphasis> → <Emphasis Type="Italic">C</Emphasis>

The applicability of the Encounter Theory (ET) (the prototype of the Collision Theory) concepts for widely occurring diffusion assisted irreversible bulk reaction A + B →C (for example, radical reaction) in dilute solutions taking account of initial microscopic correlations and force interactions between reactants has been treated theoretically with modern many-particle method for the derivation of non-Markovian binary kinetic equations. The method shows that taking into consideration initial correlations and force interactions leads to the redefinition of the Markovian rate constant only in the expressions derived earlier. Thus, just as in the reaction A + A →C and the reaction A + B →C neglecting force and initial correlations, the Modified Encounter Theory (MET), when reduced to equations of a Regular Form, both extends the time applicability range of ET homogeneous rate equation, and yields the inhomogeneous equation of the Generalized Encounter Theory (GET). It reveals macroscopic correlations induced by the encounters in the reservoir of free walks in full agreement with physical considerations. Time accumulation of macroscopic correlations obeys the same time law as in the previously considered case neglecting force interactions. Just the rate of the process will change, according to traditional redefinition of the steady-state constant of the reaction.     

Oxidation of reaction products of <Emphasis Type="Italic">p</Emphasis>-aryl-<Emphasis Type="Italic">С</Emphasis>,<Emphasis Type="Italic">С</Emphasis>-disubstituted nitrones and dimethyl 3-methylenecyclopropane-1,2-dicarboxylate

Oxidation with 2,3-dichloro-4,5-dicyanobenzoquinone of 2,4-dihydro-1Н-azeto[1,2-a]quinoline-3,4 -dicarboxylates obtained in the reaction of N-aryl-С,С-disubstituted nitrones with Feist’s acid ester resulted in the formation of 2-vinylquinoline-3,4-dicarboxylates in good yields.     

Phase Diagrams of the <Emphasis Type="Italic">n</Emphasis>-Decane–<Emphasis Type="Italic">n</Emphasis>-Hexadecane–Cyclododecane, <Emphasis Type="Italic">n</Emphasis>-Decane–Cyclododecane,and <Emphasis Type="Italic">n</Emphasis>-Hexadecane–Cyclododecane Systems

The n-decane–n-hexadecane–cyclododecane, n-decane–cyclododecane, and n-hexadecane–cyclododecane systems are studied by means of low-temperature differential thermal analysis using a differential scanning heat flow calorimeter. It is noted that all studied systems belong to the eutectic type. It is concluded that in the n-decane–n-hexadecane–cyclododecane system, the eutectic composition contains 85.0 wt % n-С₁₀Н₂₂, 4.0 wt % n-С₁₆Н₃₄, and 11.0 wt % С₁₂Н₂₄. It has a melting point of ?35.0°C.     

Determination of the <Emphasis Type="Italic">R</Emphasis> ⇄ <Emphasis Type="Italic">S</Emphasis> enantiomerization barrier in 5,6-dihydrobenzoimidazo[1,2-<Emphasis Type="Italic">c</Emphasis>]quinazolines

Chiral imidazoquinazolines undergoing thermally induced reversible R ⇄ S enantiomerization have been synthesized by the interaction of 2-(o-aminophenyl)benzimidazoles with aldehydes and ketones. The benzimidazole fragment has been used for the first time as an indicator group in temperature-dependent ¹H NMR spectra for determining the energy barrier of this rearrangement. The effects of nearby substituents on the kinetic and activation parameters, and on the recyclization mechanism have been investigated.     

New “s<Emphasis Type="Italic">p</Emphasis><Superscript><Emphasis Type="Italic">2</Emphasis></Superscript>-bonded” carbanucleosides

By reaction of 2,3-dichloro-, 2,3,5-trichloro-, 2,5-dichloro-3-phenylsulfonyl-, 2-chloro-3-phenylsulfonyl-4,4-ethylenedioxycyclopent-2-en-1-ones with uracyl 3- and 2-uracyl derivatives were obtained of the corresponding chlorocyclopentenone.