An Inorganic-Organic Hybrid Supramolecular Hydrogen-Bonding and π-π Stacking Network Containing Ge4S4− 10 Cluster: Synthesis and Characterization of (H2bipy)2Ge4S10⋅(bipy)⋅7H2O (bipy=4,4′-bipy)

The reactions of TMA₄Ge₄S₁₀ (TMA=tetramethylammonium), Cu(NO₃)₂3H₂Oand 4,4-bipy under hydrothermal environment result in the formation of (H₂bipy)₂Ge₄S₁₀(bipy)7H₂O (1), which has been structurally characterized by single crystal X-ray analysis. The 3-D structure of 1 can be viewed as an inorganic-organic hybrid supramolecular hydrogen-bonding (hydrogen bonds: O–HO, N–HN, C–HO, N–HO, and O–HS) and - stacking network containing Ge₄S^4– ₁₀ clusters and novel [H₂bipybipyH₂bipy] trimers.     

Reaction of 2-methyl-4,5-dihydrofuran with hydrogen chloride

Reaction of 2-methyl-4,5-dihydrofuran with HCl at 0°C yields 5-chloro-2-pentanone (13%) and 1-(2-methyltetrahydrofuryl-2)-5-chloro-2-pentanone (27%) and at 200° 5-chloro-2-pentanone exclusively.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. I. M. Gubkin State Petroleum and Gas Academy, 117917 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 9, pp. 2188–2191, September, 1992.     

Synthesis of some 5′-O-amino acid derivatives of uridine as potential inhibitors ofUDP-glucuronosyltransferase

Summary In an attempt to develop potential inhibitors ofUDP-glucuronosyltransferase, some 5-O-amino acid derivatives of uridine were synthesized. N-protectedL-amino acids were coupled at the 5-O-position of 2,3-O-isopropylideneuridine by esterification employing the method of symmetrical anhydrides in presence of 4-dimethylaminopyridine, 5-O-(N-benzyloxycarbonyl-O-tert.butyl-L-threonl)-23-O-isopropylideneuridine (1), 5-O-(N-tert.butyloxycarbonyl-O-benzyl-L-seryl)-2,3-O-isopropylideneuridine and (2), 5-O-(N-tert.butyloxycarbonyl-L-valyl)-2,3-O-isopropylideneuridine (3), and 5-O-(N-tert.butyloxycarbonyl-L-valyl)-2,3-O-isopropylideneuridine (4) were obtained in good yield after column chromatography on silica gel. The treatment of2 withTFA/CH₂Cl₂ (6:1) at room temperature for 30 min led to a selective removal of theBoc group without deblocking of the 2,3-O-isopropylidene group of uridine. Treatment of2 withTFA/H₂O (5:1) at room temperature for 1 h, however, released bothBoc and 2,3-isopropylidene groups. TheZ group of1 was deprotected by catalytic hydrogenolysis over 10% Pd/C/ammonium formate.

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Synthese von 5-O-Aminosäurederivaten des Uridins als potentielle Inhibitoren derUDP-Glukuronosyl-Transferase

Zusammenfassung In einem Versuch, potentielle Inhibitoren derUDP-Glukuronosyl-Transferase zu entwickeln, wurden einige 5-O-Aminosäurederivate des Uridins synthetisiert. N-GeschützteL-Aminosäuren wurden durch Veresterung mit der 5-O-Position des 2,3-isopropylidenuridins gekuppelt (Methode der symmetrischen Anhydride in der Gegenwart von 5-Dimethylaminopyridin). Solcherweise wurden 5-O-(N-Benzyloxycarbonyl-O-tert.butyl-L-threonly)-2,3-O-isopropylidenuridin (1), 5-O-(N-tert.Butyloxycarbonyl-O-benzyl-L-seryl)-2,3-O-isopropylidenuridin (2), 5-O-(N-tert.Butyloxycarbonyl-L-leucyl)-2,3-O-isopropylidenuridin (3) und 5-O-(N-tert.Butyloxycarbonyl-L-valyl)-2,3-O-isopropylidenuridine (4) nach Säulenchromatographie (Kieselgel) in guter Ausbeute hergestellt. Die Behandlung von2 mitTFA/CH₂Cl₂ (6:1) bei Zimmertemperatur (30 min) führte zu einer selektiven Abspaltung derBoc-Gruppe ohne Deblockierung der 2,3-O-Isopropylidengruppe des Uridins. Eine Behandlung von2 mitTFA/H₂O (5:1) bei Zimmertemperatur für 1 Stunde führte hingegen zur Abspaltung sowohl derBoc als auch der 2,3-O-Isopropylidengruppe. DieZ-Gruppe von1 wurde durch katalytische Hydrogenolyse auf 10% Pd/C/Ammoniumformiat abgespalten.

     

1H-NMR Investigation of the Binding of 2-Methylnaphthalene to α-Cyclodextrin in D2O Solutions

As -cyclodextrin (-CD) was added to D₂Osolutions of 2-methylnaphthalene, its proton signals shifted to lower fieldsat low concentrations of -CD. At 2.0 × 10^-2 moldm^-3 of -CD, however, a reverse, higher-field shift wasobserved for the H-8 signal, indicating the formation of 1 : 1 and 2 : 1-CD–2-methylnaphthalene inclusion complexes. Intrinsic chemicalshift differences of all the protons in 2-methylnaphthalene have beenevaluated for both the 1 : 1 and the 2 : 1-CD–2-methylnaphthalene inclusion complexes. These intrinsicchemical shift differences suggest that the first -CD molecule has noselectivity in accommodating one end of uncomplexed 2-methylnaphthalene;-CD binds to a methyl group, as well as a naphthalene ring-end havingno methyl group, to form the 1 : 1 inclusion complex, resulting in theformation of two kinds of 1 : 1 complexes.     

Isomerization of (Het)arylbenzoins in Basic Media

The isomerization of the hetaryl analogs of unsymmetrical benzoins on heating in basic media is a convenient preparative method for the production of -hydroxyacyl derivatives of -excessive heterocycles. The motivating force here for the isomerization is the formation of a thermodynamically more stable product. It was established that isomerization is promoted by increase in the difference between the electron-donating characteristics of the (het)aryl residues     

Ab initio studies of the low-lying π-states of borazine

Self-consistent-field and configuration-interaction studies were performed on borazine, using a double-zeta basis set augmented by six diffuse -functions. Low-lying singlet and triplet states of the A ₁ , A ₂ and E species were calculated, corresponding to ^* excited valence and Rydberg states. A selection out of singly and doubly excited configurations relative to a set of reference configurations was made for each species. Calculated vertical excitation energies (in eV) are 7.12 for ¹ A ₂(V), 8.45 for ¹ E (3p-R), 8.57 for ¹ A ₁(V), 8.9 for ¹ E(V-R), 9.55 for ¹ E(3d-R), 6.98 for ³ A ₁(_V), 7.27 for ³ E(V), 7.82 for ³ A ₂(V), 8.30 for ³ E(3p-R), and 9.5 for ³ E(3d-R), where V and R refer to valence or Rydberg character. The results are compared with experimental excitation energies, previous ab initio studies of borazine, and with recent ab initio studies of benzene.Dedicated to Professor Dr. H. Hartmann on the occasion of his 65th birthday.     

Die Acetalgruppe, 1. Mitt. Acetale von Halogenmethyl-arylcarbinolen

Several halomethyl-arylcarbinols were prepared, and the influence of substituents on enantiomer selectivity in the acetalisation reaction with [2S-(2,3a,4,7,7a)]-octahydro-7,8,8-trimethyl-4,7-methanobenzofuran-2-ol was examined.

Unserem sehr verehrten Lehrer, Herrn Prof. Dr.Otto Hromatka, mit den besten Wünschen zum 80. Geburtstag gewidmet.     

Cross Aldolization Between Benzaldehyde and n-Heptaldehyde to α-Pentylcinnamaldehyde Overcalcined mg-al Hydrotalcites

Calcined Mg-Al hydrotalcites (CHT) with various Mg/Al atomic ratios were prepared and characterized by XRD, BET and TPD of carbon dioxide. The CHT catalysts were utilized for the synthesis of -pentylcinnamaldehyde (-P_c) from benzaldehyde and n-heptaldehyde in a stirred batch autoclave reactor. An increase of Mg/Al atomic ratio of CHT samples results in the apparent enhancement of catalyst basicity with concomitant decrease of surface areas. Both the catalytic activity and the -P_c selectivity increase with the catalyst basicity and the reaction temperature.     

Synthesis of 2,3-disubstituted 4-oxo-3,4,5,6-tetrahydrospiro-(benzo[h]quinazoline-5,1′-cyclopentanes)

3-Substituted 4-oxo-2-thioxo-1,2,3,4,5,6-hexahydrospiro(benzo[h]quinazoline-5,1-cyclopentanes) were obtained by the reaction of 4-amino-3-ethoxycarbonyl-1,2-dihydrospiro(naphthalene-2,1-cyclopentane) with methyl, phenyl, and benzyl isothiocyanates and cyclization of the obtained thioureas. Condensation of the products with various halides gave 2,3-substituted 4-oxo-3,4,5,6-tetrahydrospiro(benzo[h]quinazoline-5,1-cyclopentanes). The reaction of 4-oxo-2-thioxo-1,2,3,4,5,6-hexahydrospiro(benzo[h]quinazoline-5,1-cyclopentane) with 1,2-dibromoethane and 1,3-dibromopropane led to 6-oxo-7,8-dihydrospiro(benzo[h]thiazolidino[2,3-b]quinazoline-7,1-cyclopentane) and 7-oxo-8,9-dihydrospiro(benzo[h]-perhydrothiazino[2,3-b]quinazoline-8,1-cyclopentane) respectively.A. L. Mndzhoyan Institute of Fine Organic Chemistry, National Academy of Sciences of the Republic of Armenia, Erevan. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 663–667, May, 2000.     

Synthesis and X-Ray Crystal Structure Study of ]2-Methyl-4-(2-methylbenzoyl)-phenoxy] Acetic Acid Hydrazide

Benzophenone analog 3 has been synthesized and characterized by the X-ray diffraction (XRD) method. The compound crystallizes in a monoclinic space group P2₁/c with cell parameters a = 7.701(8) Å, b = 7.151(5) Å, c= 28.323(3) Å, = 104.639(4)°, Z = 4. The structure exhibits intra- and intermolecular hydrogen bonding of the type N–HO, C–HO, and N–HN. The molecules are interlinked through hydrogen bonds forming an infinite chain. This polymeric-like structure may play an important role in biological activity.     

Synthesis of a Calix[4]arene Containing 'Hard' and 'Soft' Metal Ion Binding Sites

Co-receptor 1,3-calix[4]-di(aza-benzo)crown-crown-6 (1-H) designed with one calix[4]arene in a 1,3-alternate conformation and hard and soft metal ion binding sites has been prepared according to three pathways (A-C). Pathway B, consisting of two different 1 + 1 condensations with ditosylate derivatives, was shown to be the most efficient.     

Extraction-spectrophotometric determination of iron with 2-(2′-benzothiazolylazo)-4,6-dimethylphenol

An extraction-spectrophotometric method for the determination of trace amounts of iron based on its extraction into chloroform with 2-(2-benzothiazolylazo)-4,6-dimethylphenol (BTADMP) from a pH 6.5 medium has been developed. The extracted 12 FeBTADMP complex species allow the determination of 4–30gmg of iron (=3.92×10⁴1·mol^–1·cm^–1 at 790 nm). The method is highly selective and has been applied to the determination of iron in polymineral-polyvitamin pharmaceutical products.     

The electronic structure of molecules by a many-body approach

The vertical valence ionization potentials of cyclopropane, ethylene oxide and ethylene imine are calculated by a many-body Green's function method. For C₃H₆ the ordering of the ionization potentials is 2e(), 1e(), 2a₁(), 1a₂(), 1e(). The assignment of the 2a₁ and the 1a₂ ionization potentials which has been controversial is thus clarified. The ordering is in agreement with the result obtained via Koopmans' theorem. For ethylene oxide and ethylene imine Koopmans' theorem fails in predicting the correct order of ionic states. For C₂H₄O the ordering of the ionization potentials is 2b ₁(), 4a ₁, 1a ₂(), 2b ₂,3a ₁, 1b ₁(), 1b ₂, 2a ₁ and for C₂H₅N 6a, 5a, 3a, 2a, 4a, 3a, 1a, 2a. The agreement of the computed ionization potentials with the experimental values is very satisfactory.     

Natural product chemistry. Part 121. Synthesis of dicoumarinyl ethers with the structures proposed for fatagarine and oreojasmine

Synthesis of the 7,8-dicoumarinyl ethers: 7-methoxy-7,8-oxydicoumarin and 6,7-dimethoxy-7,8-oxydicoumarin, established that the structures of fatagarine and oreojasmine for which these two structures have been proposed, have to be revised. Synthesis of 7-methoxy-5,7-oxydicoumarin and 8-methoxy-7,7-oxydicoumarin exclude the possibility of these dicoumarinyl ether structures for fatagarine.

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Naturstoffchemie. 121. Mitt.: Synthese von Dicumarinylethern mit den für das Fatagarin und das Oreojasmin vorgeschlagenen Strukturen

Zusammenfassung Durch die Synthese der 7,8-Dicumarinylether: 7-Methoxy-7,8-oxydicumarin und 6,7-Dimethoxy-7,8-oxydicumarin, ließ sich nachweisen, daß die für das Fatagarin und Oreojasmin vorgeschlagenen Strukturen revidiert werden müssen. Die Darstellung des 8-Methoxy-7,7-oxydicoumarin und 7-Methoxy-5,7-oxydicumarin schließen die Möglichkeit dieser Strukturen für das Fatagarin aus.

     

Electrochemical oxidation of tetramethyl esters of α,α,ω,ω-alcaneteracarboxylic acids

Cyclization of esters of butane-1,1,4,4- and pentane-1,1,5,5-tetracarboxylic acids during electrolysis in methanol in the presence of Nal produces, with a yield of 95%, the esters of cyclobutane-1,1,2,2- and cyclopentane-1,1,2,2-tetracarboxylic acids. Under similar conditions, esters of the highest ,,,-alkanetetracarboxylic acids undergo iodation and hydroxymethylation due to electrical oxidation of methanol to formaldehyde. During electrolysis in methanol in the presence of NaOAc, the esters of ,,,-alkanetetracarboxylic acids undergo effective hydroxymethylation, followed by cyclization into substituted five- and six-member lactones, or tetrahydrofurans when structurally possible.N. D. Zelinskii Institute of Organic Chemistry, Russian Academy of Sciences, 117913 Moscow. Translated from Izvestiya Akademii Nauk, Seriya Khimicheskaya, No. 10, pp. 2332–2339, October, 1992.     

Kinetics and mechanism of the hydrolysis of sodium carboxymethylcellulose (Na-CMC) by a cellulase complex

TheSomogyi-Nelson colorimetric method is applied in a new manner more suitable for evaluating the kinetics of the enzyme hydrolysis of sodium carboxymethylcellulose (Na-CMC) catalyzed by the cellulase complex. By means of selective inhibition of a chosen enzyme from the cellulase complex it became possible to trace the effect of the other enzymes included in its composition.

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Kinetik und Mechanismus der Hydrolyse von Natriumcarboxymethylcellulose (Na-CMC) durch einen Cellulase-Komplex

Zusammenfassung Die kolorimetrische Methode nachSomogyi undNelson wird nach einem neuen Verfahren zur Verfolgung der Kinetik der hydrolytischen Spaltung von Natriumcarboxymethylcellulose (Na-CMC), katalysiert durch den Cellulase-Komplex, angewandt. Durch selektive Inhibierung eines bestimmten Enzyms des Cellulase-Komplexes kann man die Wirkung der anderen zu seiner gesamten Zusammensetzung gehörenden Enzyme verfolgen.

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Symbols Used E enzyme (E—cellulase;E—exo-cellobiohydrolase;E—-glucosidase) - [E] _w weight concentration of enzymeE - S substrate (Na-CMC—sodium carboxymethylcellulose) - [S]₀ weight concentration of substrateS - I inhibitor (I—lactose;I—calcium chloride;I—condurrite-B-epoxide) - P product (P—oligosaccharides;P—cellobiose;P—D-glucose) - P end product (K , K , K ) - DP degree of polymerization - DS degree of substitution - ES enzyme-substrate complex (E S, E S, E S) - EP enzyme-product complex (E P, E P) - EI enzyme-inhibitor complex (E I, E I, E I) - M _s molecular mass of substrateS - K _s substrate constant (K _s , K _s , K _s ) - K _I inhibitor constant (K _I , K _I , K _I ) - K _m Michaelis-Menten constant - k ₊₁,k ₊₂ (k ₊₂ ,k ₊₂ ,k ₊₂ ) forward rate constants - k _–1 reverse rate constant - ₀ initial rate of reaction - V maximal reaction rate - A change in absorbance - molar absorption coefficient - wavelength Herrn Prof. Dr.Hans Tuppy zum 60. Geburtstag herzlichst gewidmet.     

Solvent/water partitioning of dimethylmethylphosphonate (DMMP) as a probe of solvent acidity

Experimentally determined partition coefficients for DMMP between NaCl-saturated water and 20 solvents were correlated using the solvatochromic parameters , , and ^*. An inverted LSER was then used to predict for 7 additional solvents. The new cohesion parameters and ^*2 were found to be more representative of cavity formation than _H ² . Most importantly, it was essential to include either or _H ² in the LSER. The partition method appears to be a useful adjunct to solvatochromic techniques in refining and extending the scale of solvent acidity and could be used to rationalize solvent selection in extraction processes.     

Membrane transport of dicarboxylic and α-hydroxy carboxylic acids induced by α-amino phosphonates

New -amino phosphonates containing different alkyl and aryl substituents at the -carbon atom were synthesized in high yields by the Kabachnik—Fields and Pudovik reactions. These compounds were studied as carriers of several -hydroxy carboxylic and dicarboxylic acids through liquid impregnated membranes. These -amino phosphonates studied are capable of molecular recognition of oxalic acid among structurally similar -hydroxy carboxylic and dicarboxylic acids. The efficiency and selectivity of mass transfer of oxalic acid increase with an increase in the lipophilicity of the -amino phosphonate.     

Solid-Phase Extraction and Spectrophotometric Determination of Trace Amounts of Mercury in Natural Samples

A sensitive and selective solid phase spectrophotometric method for the determination of trace amounts of inorganic mercury is described. Hg²⁺ was sorbed on a silica gel-packed column as an Hg²⁺–N,N-bis(2-mercaptophenyl)ethanediamide (H₂L) complex. The Hg²⁺ complex was eluted from the column using 7mL of acetone. Various parameters including pH, column flow rate, and ligand concentration were optimized. The complex was found to obey Beers law from 2.3 to 73.7µgmL^–1 within the optimum range when the preconcentration factor was two. The effective molar absorption coefficient at 523nm was 1.17×10³Lmol^–1cm^–1 at 523nm. The concentration limits in Beers law dropped from 0.09 to 2.95µgmL^–1 within the optimum range when the preconcentration factor was 50. The relative standard deviation at a concentration level of 5µgmL^–1 Hg²⁺ (9 repetitive determinations) was 1.6%. The detection limits are 0.34µgmL^–1 and 0.015µgmL^–1 when the preconcentration factors are 2 and 50, respectively. The method has been used for routine determination of trace levels of Hg²⁺ in natural waters. The potential application of this method for the removal of Hg²⁺ from natural samples (sea water and lake water) spiked with 100ngmL^–1 of Hg²⁺ was studied. In order to validate the proposed method, LGC 6156 (harbour sediment – extractable metals) was analysed by this method. The results proved that excellent extraction of Hg²⁺ from both natural water samples was obtained by solid phase extraction using N,N-bis(2-mercaptophenyl) ethanediamide.     

Diffraction and XPS studies of Cu complexes of intercalated compounds of α-zirconium phosphate. I: Derivation of structural models from powder diffraction data

Reasonable structural models are proposed for the Cu complexes of two intercalated compounds of -Zr(HPO₄)₂·H₂O (-ZrP): one with 1,10-phenanthroline (A) and the other with 2,2-bipyridyl (B). The models are derived from considerations of the unit-cell geometry changes undergone by -ZrP upon insertion of, first, the organic molecules and then copper, in accordance with a set of general criteria of structural analysis called the comparison method.