bluuebunny/crossref_metadata_2025 huggingface dataset:
Comparison of the kinetics of bisphenol A synthesis on promoted and unpromoted ion exchanger catalysts
Authors: Jeřábek Karel , Hun Li Gwang , Setínek Karel
Published: May 2010

Previously evaluated kinetics of the synthesis of bisphenol A on ion exchanger catalyst modified by partial neutralization of its acidic groups by 2-mercaptoethylamine was compared with kinetics of this reaction on unmodified ion exchanger. Beside the differences in observed reaction rates, there was found only a small influence of the promoter on the form of the kinetics. The effect of 2-mercaptoethylamine as a heterogenized promoter, corrected for the influence of the diminishing of the concentration of acidic groups due to their neutralization by the promoter, was found to be comparable with the effect of ethylmercaptane as a homogeneous promoter.
Kinetics of hydrogenation amination of 2-propanol with aniline on a copper-chromium catalyst
Authors: Dlouhý Jiří , Pašek Josef
Published: May 2010

The kinetics of hydrogenation amination of alcohols in the liquid phase were studied in the presence of a copper(II)-chromium(III) catalyst, 2-propanol and aniline were used as the models. In addition to the kinetic investigation of the model reaction as a whole, the partial reaction steps-dehydrogenation of 2-propanol and condensation of aniline with acetone-were also examined. It was proved that, in the reaction of aniline with 2-propanol on the copper-chromium catalyst, the formation of acetone is equilibrium-controlled. The overall rate of amination of 2-propanol with aniline is determined by both the condensation of acetone with aniline and the hydrogenation of the ketimine intermediate. The amination is accelerated by addition of aluminosilicate to the copper-chromium catalyst, which confirms that the ketimine concentration is not equilibrium-controlled.
Reaction of N-methyl-N-(2,4-dinitrophenyl)glycine methylamide with methoxide
Authors: Macháček Vladimír , Sebránek Miloslav , Štěrba Vojeslav
Published: May 2010

The side reactions of N-methyl-N-(2,4-dinitrophenyl)glycine methylamide with methanolic sodium methoxide reversibly give the spiro adduct (spiro[(1,3-dimethyl-5-imidazolidone)-2,1'-(2',4'-dinitrobenzenide)]) and irreversibly produce N-methyl-2-nitroso-4-nitroaniline which undergoes subsequent reduction. The diazolidine ring of the spiro adduct is opened by action of methanolic hydrogen chloride, whereby the Smiles rearrangement is completed. The rearrangement product-2-methylamino-N-methyl-N-(2,4-dinitrophenyl)acetamide hydrochloride-is present in the form of a mixture of Z and E isomers (ratio 1.9). The equilibrium constant of formation of the spiro adduct from 2-methylamino-N-methyl-N-(2,4-dinitrophenyl)acetamide hydrochloride is by 9 orders of magnitude lower than that found for the analogous trinitrophenylderivative. The rate-limiting step of the transformation of the Z-isomer into the spiro adduct consists in the isomerization Z ⇄ E. The E-isomer is cyclized with a half-life shorter than 1 ms.
Oligophenylene 2,4,6-triarylpyridines and analogous diaza-p-terphenyls, diaza-p-quaterphenyls and diaza-p-quinquephenyls with luminiscent activity
Authors: Kurfürst Antonín , Lhoták Pavel , Petrů Miroslav , Kuthan Josef
Published: May 2010

Cyclocondensation of α,β-unsaturated aromatic ketones V and VIII with quaternary pyridinium salts VI in the presence of ammonium acetate gave 2,4,6-triarylpyridines I, aryl-substituted diaza-p-terphenyls IIa,b, diaza-p-quaterphenyls IIc,d and diaza-p-quinquephenyls IIe,f. All the new polyphenylene compounds exhibit characteristic luminiscence in the visible spectral region.
Isolation and structures of sesquiterpene lactones: Aerial parts of Arctotis grandis THUNB. species
Authors: Buděšínský Miloš , Le Viet Ngoc Phuong  , Perez Souto Nestor , Daniewski Włodzimierz M. , Wawrzuń Andrzej , Gumułka Maria , Vašíčková Soňa , Šaman David , Drożdż Bohdan , Grabarczyk Halina , Rychłewska Urszula , Holub Miroslav
Published: May 2010

Arctolide (I), together with seven other sesquiterpene lactones II, IV-IX, was isolated from aerial parts of Arctotis grandis THUNB. species. Structures, including absolute configuration, have been assigned to the isolated compounds. Compounds VI and VIII were also isolated from Vernonia angusticeps EKM.
Synthetic segments of influenza virus haemagglutinins
Authors: Ježek Jan , Bláha Ivo , Zaoral Milan , Hamšíková Eva , Závadová Hana , Vonka Vladimír
Published: May 2010

Ala97HA-1 (91-108) (I), Met97HA-1 (91-108) (II), HA-2 (1-13) (III), HA-1 (185-200) (IV) segments of influenza virus Victoria/75 (H3N2) haemagglutinins were prepared by solid phase peptide synthesis and conjugated to TT and BSA, respectively. The conjugates were tested for immunogenicity in rabbits.
Crystal structures bonds and reliance in MX (M = La, Ce...Yb and Sc, Ti...Zn; X = S, Se, Te)
Authors: Oudet Xavier
Published: May 2010

Large variations of the molecular volume of the monochalcogenides of rare earths are attributed to cation-cation bond which involves one deep valence electron. Similar results are found with monochalgenides of 3d metals. The phase transformation Ceγ ⇄ Ceα is interpreted in a similar way bearing in mind the existence of compounds such as XeF4. This work introduces the notion of reliance which enlightens the notion of valence and is closely related, to the notion of intermediate and fluctuating valences.
Simple amidinium carboxylates - An MO treatment of molecular geometry and electronic structure
Authors: Krechl Jiří , Böhm Stanislav , Smrčková Svatava , Kuthan Josef
Published: May 2010

Carboxylates of amidines (I, II), substituted guanidine (III) and iso(thio)ureas (IV, V) were prepared. Nonempirical quantum chemical treatment of the electronic structure of simple compounds I-V, based on total molecular geometry optimization, their preparation and physico-chemical data are reported. Interaction between the two amidinium nitrogens and carboxylate oxygens is mediated by hydrogen bonds and alternation of charge distribution.
Atriopeptins. I. Synthesis of C-terminal fragments
Authors: Ovchinnikov Mikhail V. , Bespalova Zhanna D. , Molokoedov Aleksandr S. , Revenko Inna V. , Sepetov Nikolai F. , Isakova Olga L. , Titov Mikhail I.
Published: May 2010

Peptides, corresponding to the C-terminal sequence in atriopeptins, have been synthesized using classical methods of peptide synthesis in solution and chracterized by various physicochemical methods. The synthetic strategy and methods are discussed.
Hydrophobized proteins penetrating lipid membranes
Authors: Kabanov Alexander V. , Levashov Andrei V. , Alakhov Valeri Yu. , Kravtsova Tatiyana N. , Martinek Karel
Published: May 2010

Article without abstract.
13C NMR study of the mixture MBBA/EBBA/decane: The influence of decane on the molecular ordering in the nematic phase
Authors: Šebek Josef , Teeaar Raivo
Published: May 2010

Influence of various amounts of decane dissolved in the eutectic nematic mixture in methoxybenzylidenebutylaniline and ethoxybenzylidenebutylaniline (MBBA/EBBA) on the ordering and structure of mesomorphic molecules has been determined employing high-resolution proton enhanced 13C NMR spectroscopy. The obtained results are compared with temperature behaviour of the ordering and structure of EBBA studied by means of the same technique. Slight differences in the ordering of the phenyl parts of molecules in the dependence on temperature and on decane concentration have been observed. This contrasts with great differences observed in the behaviour of the butyl parts of mesogenic molecules. Two possible explanation of the behaviour of butyl chain atoms in the dependence on decane concentration are presented. According to one approach, conformational order parameters of the first butyl carbons increase with the increasing decane concentration. Another possibility is that decane increases the correlation between the whole molecule rotation and the internal rotation around the first butyl bond.
Infrared spectroscopic study of the hydration of porous glass
Authors: Ivanek Ondřej , Schmidt Pavel , Schneider Bohdan
Published: May 2010

Infrared spectra of mesoporous and macroporous siliceous glasses were measured in the native state and after silylation, at various contents of H2O and D2O. By analysis of these spectra it was found that water is bound to the glass surface by strong hydrogen bonds between the water molecules and isolated Si-OH groups; capillary condensation was observed only in native mesoporous glasses.
On the electroreduction mechanism of halobenzenes: The special case of 1,2-dibromobenzene
Authors: Casado Juan , Ortega Manuel , Gallardo Iluminada
Published: May 2010

Reinvestigation of the electrochemical reduction of 1,2-dibromobenzene by polarography, cyclic voltammetry, rotating ring-disk electrode voltammetry and controlled potential electrolysis, as well as theoretical calculations, leads to the proposal of a stepwise mechanism. Experimental results for bromobenzene and 1,3-dibromobenzene are also reported for comparison.
Reactivity ratios and UV spectral characteristics of copolymers of vinyl or isopropenyl derivatives of 2-(2-hydroxyphenyl)-2H-benzotriazoles
Authors: Borsig Eberhard , Kárpátyová Angela , Vogl Otto
Published: May 2010

The preparation of polymeric UV stabilizers by copolymerization of polymerizable UV stabilizers like 2-(2-hydroxy-5-vinylphenyl)-2H-benzotriazole (2H5V) and 2-(2-hydroxy-5-isopropenylphenyl)-2H-benzotriazole (2H5P) with styrene (S), methyl methacrylate (MMA), and butyl acrylate (BA) was studied. Copolymerization parameters for six pairs of monomers, i.e. 2H5V-S, 2H5V-MMA, 2H5V-BA, 2H5P-S, 2H5P-MMA, and 2H5P-BA and UV spectra of the 2H5P copolymers were determined. The effect of stiffness of the polymer chain on UV spectra of copolymers studied is discussed.
Conversion of betulin into careyagenolide (2α,3β-dihydroxy-18α,19βH-ursan-28,20β-olide)
Authors: Sejbal Jan , Klinotová Eva , Bludská Markéta , Klinot Jiří , Buděšínský Miloš
Published: May 2010

Careyagenolide (I) and its respective 2β,3α- and 2β,3β-isomers XVII and XIV were prepared from 3-oxo-18α,19βH-ursan-28,20β-olide (IX), accessible from betulin (II). The key step of the synthesis was hydroxylation of ketones IX and X with 3-chloroperoxybenzoic acid and reduction of ketones XI-XIII.
Bis(monoazacrown ethers) with an electron-donating substituent at the hinge: A pronounced participation of hydroxyl group in formation of sodium ion sandwich complexes
Authors: Závada Jiří , Koudelka Juraj , Holý Petr , Bělohradský Martin , Stibor Ivan
Published: May 2010

Sodium ion complex formation has been investigated potentiometrically in four homologous bis(crown) series I-IV differing by the nature of substituent placed at the linking trimethylene chain (X = OH, OCH3, OCH2C6H5 and H respectively). A marked enhancement of the complex stability has been observed in the bis(crown) series I and attributed to participation of the lateral hydroxyl group in the sandwich complex formation. Evidence in support of the sandwich structure has been provided (i) by analysis of the potentiometric data indicating a 1:1 complex stoichiometry and (ii) by a comparison of the complex stability data from the bis(crown) series I with the corresponding values from related monocyclic ligand series V, VI and VII revealing a pronounced cooperation of both macrorings in the sodium ion-bis(crown) I complex formation.
13C NMR of study of entrapping proteins (α-chymotrypsin) into reversed micelles of surfactants (aerosol OT) in organic solvents (n-octane)
Authors: Shapiro Yurii E. , Budanov Nikolai A. , Levashov Andrei V. , Klyachko Nataliya L. , Khmelnitsky Yurii L. , Martinek Karel
Published: May 2010

Hydrated reversed micelles of Aerosol OT (AOT) in octane have been studied by 13C NMR spectroscopy. The changes of spin-lattice relaxation times (T1) for individual segments of the AOT molecule, induced by entrapping a protein (α-chymotrypsin) into the micelle, have been determined by the inversion-recovery technique. The dramatic (three-fold) increase of T1 found for the α-CH2 groups in the AOT molecules indicates that (unlike in the unfilled micelle) in the protein-containing micelle the boundary of the water cavity is shifted outward (0.5-0.7 nm, under the given experimental conditions), the alkyl chains of the surfactant being “flooded” by water molecules. This observation explains why the outer size of the reversed micelle does not change on insertion of a bulky protein molecule.
Crystal structure of (E)-1,2-bis(butylsulfonyl)ethylene
Authors: Podlaha Jaroslav , Podlahová Jana , Hašek Jindřich
Published: May 2010

The title compound is orthorhombic, space group Pbca, a = 8.523(1), b = 17.467(3), c = 9.449(1) Å, Z = 4, R = 0 052 for 878 observed reflections. The molecule is centrosymmetric with inversion at the middle of the double bond. The characteristic feature of the structure is an almost exactly planar O-S-C(H)=C'(H')-S'-O' moiety with the H···O' and H'···O distances of 2.55 Å, indicating much more weaker intramolecular hydrogen bonds than in the related ethylsulfonyl derivative studied earlier.
Antiandrogenic A-homo-B,19-dinor-analogues of androgens from 6β-chloro-5-methyl-19-nor-5β-androst-9-enes
Authors: Kasal Alexander
Published: May 2010

6β-Chloro derivatives of 5-methyl-19-nor-5β-androst-9-enes (Westphalen diol type) with oxygen functionalities in positions 3 and 17 were converted into diene VI by treatment with lithium aluminium hydride. The lipophilic product of hydrogenation of VI was shown to be 4aα-methyl-A-homo-B,19-dinor-5β,10α-androstane-3β,17β-diol (IX). Various paths leading to dihydrotestosteron analogues, e.g. selective acylation or oxidation of diol IX and partial hydrolysis of diacetate X, have been realized. 17β-Hydroxy-4aα-methyl-A-homo-B,19-dinor-5β,10α-androstan-3-one (XVI) has been found to exhibit antiandrogenic activity.
Synthesis and spectral properties of pyrrolo[3',4':5,6]-4H-pyrano[2,3-d]pyrimidine derivatives
Authors: Marchalín Štefan , Pavlíková Františka , Ilavský Dušan
Published: May 2010

The starting 2-amino-5-ethoxycarbonyl-6-chloromethyl-4-(2-furyl)-3-cyano-4H-pyran (I) afforded on condensation with triethoxymethane 2-ethoxymethylenamino-4H-pyran II; treatment of the latter with ammonia yielded 2-formamidino-3-cyano-4H-pyran III, which, when heated in dilute ethanol, cyclized to 4-amino-6-ethoxycarbonyl-5-(2-furyl)-7-chloromethyl-4H-pyrano[2,3-d]pyrimidine (IV). Compound IV reacted with alkyl- or arylamines to give substituted 5H,6H,8H-pyrrolo[3',4':5,6]-4H-pyrano[2,3-d]pyrimidines VI, one of which (VIb, R = p-CH3C6H4) was alternatively obtained from 2-formamidino-4H-pyrano derivative III. The structures of new tricyclic heterocycles were corroborated by analysis of the NMR spectral data.
A modification of the Redlich-Kwong-Soave equation of state and the determination of its parameters on the basis of saturated vapour pressures and second virial coefficients of pure substances
Authors: Voňka Petr , Dittrich Pavel , Novák Josef P.
Published: May 2010

The temperature dependence of parameter a = a(Tr) of the Redlich-Kwong-Soave equation of state was modified. To calculate the corresponding individual parameters, an effective algorithm applying the Newton method was proposed. The parameters were determined for 60 substances, and the new modification correlates saturated vapour pressures from the values of pr = 0.001 to pr = 1.0 with the accuracy which is usually better than 0.2% and is comparable with that attained in terms of the Wagner equation. The modification proposed is utilized above all when applying the equation of state to the calculation of vapour-liquid equilibrium.
Electrical and electrochemical chracteristics of a new type of polyacetylene films
Authors: Pfleger Jiří , Kmínek Ivan , Nešpůrek Stanislav , Papež Vítězslav , Novák Petr
Published: May 2010

The morphology, electrochemical and electrical properties of polyacetylene films, prepared with a catalytic system titanium tetrabutoxide/ethylmagnesium bromide in two forms–non-dried porous and dried compact ones–were studied. The properties of non-dried porous films as positive electrodes in lithium cells were characterized by means of cyclic voltammetry, electrochemical impedance measurements, galvanostatic cycling and “in situ” resistance measurements. The electrical conductivity of undoped dried compact films was 10-7 to 10-6 S m-1 depending on the oxygen content. Iodine doping increased the conductivity of these films up to σ = 7·6.103 S m-1, the conductivity of the trans-isomer (CHI0.27)x increased up to σ = 3.3.103 S m-1. From the temperature dependence of the electrical conductivity we have concluded that the transport of charge carriers is due presumably to the variable-range, phonon-assisted hopping of carriers between localized states, the density distribution function of which is not constant around the Fermi level.
Measurements of specific copper surface area by a pulse chromatographic technique
Authors: Dvořák Bohumír , Hudec Antonín , Pašek Josef
Published: May 2010

The method for determination of specific copper area by decompositive adsorption of N2O has been investigated using pulse chromatographic technique. The reaction is accompanied by activated adsorption of oxygen. The amount of oxygen adsorbed depends linearly upon the temperature in the range of -20 to +90 °C. The existence of an oxygen monolayer in the temperature range from 90 to 120 °C has been proved. On the surface, the Cu:O ratio is equal to 2. The rate of decompositive N2O adsorption is very high. The weakly bonded oxygen can be desorbed at 100 °C into a stream of inert gas and the rate of oxygen desorption depends on the temperature of decompositive N2O adsorption. An improved procedure for measuring copper surface area by pulse chromatographic technique have been suggested.
The polarographic and voltammetric determination of the 4'-haloderivatives of N,N-dimethyl-4-aminoazobenzene
Authors: Barek Jiří , Haladová-Bláhová Helena , Zima Jiří
Published: May 2010

The polarographic reduction of 4-haloderivatives of N,N-dimethyl-4-aminoazobenzene has been studied in mixed water-methanol medium, a mechanism has been proposed and optimal conditions have been found for determination of these substances by TAST polarography with a determination limit of about 1.10-6 mol l-1, by differential pulse polarography with a determination limit of about 1.10-7 mol l-1 and linear scan voltammetry with a determination limit of about 5.10-8 mol l-1. In the latter technique, the determined substance was accumulated by adsorption on the surface of a hanging mercury drop electrode to decrease the determination limit below 1.10-8 mol l-1.
Synthesis of poly[N5-(2-hydroxyethyl)-L-glutamines] with modified side chain
Authors: Pytela Jindřich , Rypáček František , Metalová Marie , Drobník Jaroslav
Published: May 2010

The procedure for synthesis of water-soluble polymers on the basis of poly[N5-(2-hydroxyethyl)-L-glutamine] was developed. It allows binding of various groups of interest (reactive spacers, biologically active compounds, tracers etc.) to these polymers using side chains modifications. A multi-step procedure involves partial debenzylation of poly(γ-benzyl-L-glutamate), conversion of resulting carboxyl groups to reactive succinimido ester groups, which in turn are aminolyzed by the compound of interest. The final step of the synthesis, viz., aminolysis of residual benzyl ester groups with 2-aminoethanol, leads to water-soluble modified poly[N5-(2-hydroxyethyl)-L-glutamines].
On reactivity of 2,6-dichloro-3,5-diformyl-1,4,4-trimethyl-1,4-dihydropyridine
Authors: Kurfürst Antonín , Šebek Pavel
Published: May 2010

2,6-Dichloro-3,5-diformyl-4,4-dimethyl-1,4-dihydropyridines IIb-IId have been prepared by the Vilsmeier-Haack reaction of glutarimides I, and possible chemical transformations of the trimethyl derivative IIc have been examined. The bis-oxime IVa and bis-(2,4-dinitrophenylhydrazone) Vb are formed by the respective reactions of the formyl groups. The nucleophilic substitutions of chlorine give the corresponding derivatives IX-XII. The cyclocondensation reaction of compound IIc with the respective reagents gives the condensed heterocyclic derivatives VI, XIII, and XIV. The physico-chemical characteristics of the II-XIV compounds prepared are described.
Application of cellulose paper as support material in simultaneous solid phase peptide synthesis
Authors: Eichler Jutta , Beyermann Michael , Bienert Michael
Published: May 2010

Cellulose paper was esterified with Nα-Fmoc-protected amino acid chlorides providing a chemically stable segmental support, the utility of which for simultaneous solid phase peptide synthesis was demonstrated by the synthesis of several sets of model peptides following different synthetic strategies.
Oxygen absorption into Ellis liquid in a bead column
Authors: Potůček František , Stejskal Jiří
Published: May 2010

Liquid side mass transfer coefficient was measured for absorption of oxygen in non-Newtonian liquids. The experiments were carried out in a laboratory absorption bead column in which the liquid flowed over a single vertical row of spheres without vertical spaces between elements and/or with spaces of 0.2 cm between elements. The results were described by correlation equations involving dimensionless groups modified for Ellis flow model.
Kinetics of alkaline hydrolysis and correlation studies of m- and p-substituted piperidinoethyl phenylcarbamates
Authors: Stankovičová Mária , Čižmárik Jozef
Published: May 2010

Kinetics of alkaline hydrolysis have been studied with a series of 15 m- and p-substituted piperidinoethyl phenylcarbamates. The rate constants have been determined at 70, 60, 50, and 40 °C and the activation parameters have been calculated. These values have been correlated with the substituent constants σ, F, R, F, R, π. Validity of the Hammett equation and the Swain-Lupton equation has been confirmed in the series studied and for the p-derivatives, respectively. The lipophilicity parameter π does not correlate with the values found.
Alkylation of 2,4,4,6-tetraphenyl-1,4-dihydropyridine
Authors: Schwarz Marián , Kuthan Josef
Published: May 2010

A series of photochromic N-methyl derivatives IIIa-IIIh was synthesized by alkylation of 1-sodio-2,4,4,6-tetraphenyl-1,4-dihydropyridine (II) in an inert atmosphere. On the other hand, the starting material II afforded products IVa and IVb in the presence of atmospheric oxygen. Mechanisms of acidobasic transformations of compounds IVa and IVb are discussed and spectral characteristics of new compounds are interpreted.
Synthesis of 2-propynyl ethers of steroid alcohols
Authors: Pouzar Vladimír , Schneiderová Lenka , Drašar Pavel , Štrouf Oldřich , Havel Miroslav
Published: May 2010

2-propynyl ethers, derived from steroid alcohols with hydroxyl in position 3β, 17 or 20, were prepared by reaction with propargyl bromide and sodium hydroxide under conditions of phase transfer catalysis. Other hydroxy groups in the steroid molecule were protected with the methoxymethyl or 2-tetrahydropyranyl group.
Conformation of 6-amino-6-deoxyhexonolactams
Authors: Kefurt Karel , Kefurtová Zdeňka , Trška Petr , Bláha Karel , Frič Ivo , Jarý Jiří
Published: May 2010

Eight configurational isomers of 6-amino-6-deoxyhexonolactam Ia-VIIIa and their tetra-O-acetyl derivatives Ib-VIIIb were studied using NMR and CD spectroscopy. For all the compounds most values of chemical shifts of the 1H and 13C nuclei as well as of vicinal coupling constants were obtained. Comparison of the observed values with 3J(H,H) values, calculated for various conformations of the studied compounds by a modified Karplus relationship, led to assignment of predominant conformation 1,NC4(D) or 4C1,N(D) to the lactams Ia-VIIIa and Ib-VIIIb in solution. For the measured set of compounds, the decisive conformation-determining requirement seems to be the equatorial position of substituent on the carbon next to the carbonyl group. The CD spectra of the lactams Ia-VIIIa in water, interpreted according to the currently used rules, in six cases agreed and in two cases disagreed, with the NMR results. The reasons of this discrepancy are discussed.
Synthesis of some 1-aryl-1,4-dihydro-4-oxoquinoline-3-carboxylic acids and their antibacterial activity
Authors: Rádl Stanislav , Zikán Viktor
Published: May 2010

1,4-Dihydro-4-oxoquinoline-3-carboxylic acids VIIIc and VIIId were prepared via their ethyl esters VIIIa and VIIIb, which were obtained by a direct arylation of ethyl 7-chloro-6-fluoro-1,4-dihydro-4-oxoquinoline-3-carboxylate (VIa). When treated with piperazine or N-methylpiperazine compound VIIId yields VIIIe or VIIIf, respectively. Reduction of VIIId, VIIIe, and VIIIf with ferrous sulfate yields VIIIg, VIIIh, and VIIIi, respectively. Diazotization and introduction of fluorine into VIIIg using hydrogen fluoride-pyridine yields VIIIj. The compounds prepared were tested for their antimicrobial activity in vitro.
Synthesis of N-(2-phosphonylmethoxyethyl) derivatives of heterocyclic bases
Authors: Holý Antonín , Rosenberg Ivan , Dvořáková Hana
Published: May 2010

The preparation of N-(2-phosphonylmethoxyethyl) derivatives of purine and pyrimidine bases, IV, as analogs of the antiviral 9-(2-phosphonylmethoxyethyl)adenine (PMEA, I), is described. The synthesis consists in alkylation of alkali metal salts of heterocyclic bases or their N- or O-substituted derivatives with diethyl 2-p-toluenesulfonyloxyethoxymethylphosphonate (IIa), 2-chloroethoxymethylphosphonate (IIb) or 2-bromoethoxymethylphosphonate (IIc). The obtained N-(2-diethoxyphosphonylmethoxyethyl) derivatives of heterocyclic bases (III) were treated with bromotrimethylsilane to give phosphonic acids IV. Compounds IV were prepared from pyrimidines (uracil, cytosine and their 5-methyl derivatives), purines (adenine and its N6- and C(2)-substituted derivatives, hypoxanthine, guanine, 6-hydrazinopurine and 6-methylthiopurine etc.) and their analogs (3-deazaadenine etc.).
An alternative route to 2α,3α-diols from 2,3-unsaturated 5α-steroids avoiding the use of osmium tetroxide
Authors: Černý Václav
Published: May 2010

A method for preparation of 2α,3α-dihydroxy-5α-steroids from 2,3-unsaturated 5α-steroids without the use of OsO4 is described. It involves the sequence of epoxidation, cleavage of the oxirane ring by HI, acetylation, oxidative replacement of iodine by hydroxyl and alkaline hydrolysis (I → VI) without purification of the intermediates. The presence of a 6-keto group does not decrease the yields. The yields are comparable with those obtained by osmylation and the method can find general use, particularly in the synthesis of brassinolide analogs.
Antiandrogenic A-homo-B,19-dinorandrostanes from 5β-methyl-19-norandrost-9-enes with different substituents in positions 3 and 17
Authors: Kasal Alexander
Published: May 2010

Westphalen-type derivatives II, IV and VIII were converted into derivatives of 4a-methyleno-A-homo-B,19-dinor-5β-androst-9-ene with different substituents in positions 3 and 17 (compounds XII, XIII and XV) which were utilized for the preparation of the antiandrogenic 17β-hydroxy-4aα-methyl-A-homo-B,19-dinor-5β,10α-androstan-3-one (I).
Studies on stereochemistry of thionuphlutine and neothiobinupharidine methiodides and their products of Hofmann degradation
Authors: Wróbel Jerzy T. , Scholl-Aleksandrowicz Anna , Cybulski Jacek , Wojtasiewicz Krystyna
Published: May 2010

Degradation of tetrahydrothiophene ring in two isomeric Nuphar alkaloids–thionuphlutine and neothiobinupharidine has been observed during methylation under thermodynamic control. The C-S bond has been cleaved and the double bond formed in the products of methylation. The structure and stereochemistry of methiodides and their products of Hofmann degradation have been determined by 13C NMR spectroscopy.
Potential antidepressants: 4-(Thioaryloxy)piperidines
Authors: Šindelář Karel , Hrubantová Marta , Svátek Emil , Matoušová Oluše , Metyšová Jiřina , Valchář Martin , Protiva Miroslav
Published: May 2010

Nucleophilic substitution reactions of a series of thio-substituted fluoroarenes with 1-methyl-4-piperidinol, 1-benzyl-4-piperidinol, and 1-methyl-4-phenyl-4-piperidinol in the presence of sodium hydride in dimethylformamide gave the title compounds V-XI and XIII. The salts of these bases were pharmacologically tested and salts of compounds V, XI, and XIII showed in behavioural tests properties which are indicative of antidepressant activity.
Potential anticonvulsants: 3-Chlorobenzophenone derivatives
Authors: Jílek Jiří , Urban Jiří , Kmoníček Vojtěch , Pomykáček Josef , Holubek Jiří , Svátek Emil , Matoušová Oluše , Metyš Jan , Valchář Martin , Wildt Stanislav , Protiva Miroslav
Published: May 2010

Reactions of 2-(2-iodoacetamido)-5-chlorobenzophenone with 2-amino-2-phenylethanol, 2-amino-1-phenylethanol, 3-amino-2-phenylpropanol, D-(+)-norpseudoephedrine, and 2-aminopropane-2-carbonitrile gave the 2-substituted N-(2-benzoyl-4-chlorophenyl)acetamides X-XIV. 2,3'-Dichlorobenzhydrol (XVI) and 2,3'-dichlorobenzhydryl chloride (XIX) were transformed to the ethers XVII and XVIII and to the amines XXI-XXIV. Compound XVI was oxidized to the ketone XXV which was transformed via the oxime XXVI to compound XXVII. The basic products were converted to salts which were pharmacologically tested. Compounds X, XVII, XXIII, and XXVII showed anticonvulsant effects and some other neurotropic activities.
Preparation and characterization of new analogues of Dalargin
Authors: Pospíšek Jan , Barth Tomislav , Bespalova Zhanna D. , Titov Mikhail I. , Mašková Hana P. , Molokoedov Alexander S. , Sepetov Nikolai F.
Published: May 2010

Tert-butyloxycarbonyl-O-tert-butyloxycarbonyl-L-tyrosyl-D-alanyl-glycyl-L-phenylalanyl-DL-neopentylglycyl-L-arginine was prepared by means of fragment condensation in solution. Protecting groups were removed with trifluoroacetic acid and the diastereoisomeric peptides were separated employing high-performance liquid chromatography (HPLC) and the absolute configuration of neopentylglycine in each diastereomer was determined by two different methods: analysis of enzymatic degradation with carboxypeptidase B and 1H NMR spectroscopic data. The hexapeptide with L-neopentylglycine in position 5 exhibited a 20 times higher activity in a standard test on isolated guinea-pig ileum (GPI). The hexapeptide with D-neopentylglycine in position 5 exhibited a 4 times higher activity than Dalargin in the GPI test but its effect was prolonged in comparison to the analog with L-neopentylglycine and Dalargin.
A network thermodynamic model for transient effects in electrokinetic energy conversion
Authors: González-Fernández Carlos F. , Horno José , González-Caballero Fernando
Published: May 2010

A network model is proposed allowing the transient effects in electrokinetic phenomena to be studied in terms of the network thermodynamics concept. Relaxation times for the build-up of electroosmotic pressure and streaming potential, time required for the electrokinetic energy conversion to reach its maximum efficiency and the optimum outforce for the energy conversion are readily obtained by this method.
4H-Benzo[4,5]cyclohepta[1,2-b]thiophenes and 9,10-dihydro derivatives - Sulfonium analogues of pizotifen and ketotifen; Chirality of ketotifen; Synthesis of the 2-bromo derivative of ketotifen
Authors: Polívka Zdeněk , Buděšínský Miloš , Holubek Jiří , Schneider Bohdan , Šedivý Zdeněk , Svátek Emil , Matoušová Oluše , Metyš Jan , Valchář Martin , Souček Radomír , Protiva Miroslav
Published: May 2010

Reaction of ketone IX with 4-tetrahydrothiopyranylmagnesium bromide and the following dehydration with thionyl chloride afforded the sulfide III which was transformed to the methiodide II (sulfonium analogue of pizotifen). Similar sequence starting from the ketone XXIV and concluded by dehydration of the alcohol XX, cleavage of the enol ether, and by treatment with methyl iodide resulted in the formation of the sulfonium analogue of ketotifen (V). Three modified routes leading to ketotifen (IV) are being described. The chirality of ketotifen was proven by 1H NMR spectroscopy with the help of the optically active NMR shift reagent. The resolution of racemic ketotifen (IV) was achieved by crystallization of salts with optically active O,O'-diacyltartaric acids and homogeneous enantiomers were obtained. The X-ray crystallographic analysis of (+)-IV (-)-O,O'-di(p-toluoyl)-(R)-tartarate led to the three-dimensional structure of the molecule of (+)-ketotifen which enabled to determine its absolute configuration to be (R). One of the products of bromination of the ketone IX, the following methanolysis and dehydrobromination, identified as XXVII, was transformed by reaction with 1-methyl-4-piperidylmagnesium chloride, by the following acid-catalyzed dehydration, and cleavage of the enol ether to the 2-bromo derivative of ketotifen XXXIV. (R) (+)-Ketotifen (IV) was found to be the more active ketotifen enantiomer but the stereoselectivity of its action is only a partial one. The 2-bromo derivative of ketotifen (XXXIV) is much less active than ketotifen in the line of antihistamine activity.
Activity and selectivity of carbon-supported transition metal sulfides in simultaneous hydrodearomatization and hydrodesulfurization
Authors: Hillerová Eva , Zdražil Miroslav
Published: May 2010

Hydrodesulfurization (HDS) and hydrodearomatization (HYD) activities of carbon-supported sulfides of V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Ru, Rh, Pd, W, Re, Ir, and Pt, and of the commercial Co-Mo/Al2O3 catalysts were evaluated. Simultaneous hydrodesulfurization of benzothiophene and hydrogenation of naphthalene to tetralin at pressure of 2 MPa were used as the model reaction. Platinum group metal sulfides and Re sulfide exhibited the highest HDS activity and Pd and Rh sulfides reached the activity of a good commercial Ni-Mo catalyst. Tha catalysts strongly differed in the selectivity of dihydrobenzothiophene formation during HDS; up to 55% of dihydrobenzothiophene was obtained over W sulfide, while Rh, Ni, Co-Mo and Ni-Mo catalysts produced less than 8% of it. The highest HYD activity exhibited platinum group metal sulfides; the best were Ir and Pt sulfides which were four times and three times more active than the commercial Ni-Mo catalyst, respectively. The selectivity HDA/HDS depend strongly on the type of transition metal. The sulfides of W, Ir and Pt were much more selective for HYD than the Ni-Mo catalyst, and the Co-Mo sample showed by far the lowest HDA/HDS selectivity.
Synthesis and characterization of mixed anhydrides of O-benzylbenzohydroximic acid
Authors: Sharma Namita , Misra Bhupendra Nath
Published: May 2010

Mixed anhydrides of O-benzylbenzohydroximic acid have been prepared by acylation and sulfonylation of O-benzylbenzohydroxamic acid using a variety of acyl and sulfonyl halides in the presence of trimethylamine and pyridine in dioxane and benzene. Structure elucidation of the resulting products was performed by chemical and spectroscopic methods. All evidences indicate that the products have the mixed anhydride structure with (Z)-configuration. Corresponding (E)-isomer and the isomeric N-acylated or sulfonylated products, if formed, could not be isolated. Several mixed anhydrides showed antiparasitic activity.
Stereoselective synthesis of (±)-threo-2-amino-1-(4-nitrophenyl)-1,3-propanediol
Authors: Červinka Otakar , Dudek Václav , Fábryová Anna , Kolář Jiří , Lukáč Juraj , Šimon Jan , Viktorin Martin
Published: May 2010

Addition of hypobromic acid to styrene afforded styrene bromohydrin (I) which was dehydrated to ω-bromostyrene (II). Prince reaction of II with aqueous formaldehyde gave 5-bromo-4-phenyl-1,3-dioxane (III). The bromine atom in III was replaced with amino group by treatment with methanolic ammonia at 150°C and 6–8 MPa and the obtained threo-5-amino-4-phenyl-1,3-dioxane (IVa) was hydrolyzed to give (±)-threo-2-amino-1-phenyl-1,3-propanediol (V). Suitably chosen method of nitration converted the free base IVa or its N-acetyl derivative IVb into 5-amino-4-(4-nitrophenyl)-1,3-dioxane (VIa) or its N-acetyl derivative VIb which without isolation were hydrolyzed to threo-2-amino-1-(4-nitrophenyl)-1,3-propanediol (VII), isolated as hydrochloride. The liberated base was resolved into enantiomers and dichloracetylated in the known manner to give D-(-)-threo-2-dichloracetylamino-1-(4-nitrophenyl)-1,3-propanediol (chloramphenicol).
Synthesis and use of an aminoquinolinone derivative for the fluorometric determination of oxytocinase
Authors: Mašková Hana P. , Kokotos George , Tzougraki Chryssa , Barth Tomislav
Published: May 2010

A new fluorogenic substrate for the determination of the activity of human serum oxytocinase-cystine aminopeptidase (EC 3.4.11.3), H-Cys(Bzl)-NH-Meq, has been synthesized. The affinity of H-Cys(Bzl)-NH-Meq to oxytocinase was by two orders higher than that of the usually employed chromogenic substrates. The Michaelis constant of oxytocinase for this substrate was within the range of the optimum pH (7.0–7.5) 2.3.10-6 mol l-1, i.e. in the region of the affinity of the natural substrate, oxytocin. The concentration of dimethylsulfoxide used for the solubilization of H-Cys(Byl)-NH-Meq (<0.4%) did not influence adversely the course of the enzyme reaction as in the case of chromogenic substrates, where the concentrations of the organic solvent exceeded 3%.
Temperature dependence of saturated vapour pressures of methyl isobutyl ketone, diisobutyl ketone, 1,1-difluorotetrachloroethane, and 1,2-difluorotetrachloroethane
Authors: Svoboda Václav , Adamcová Zdena , Kubeš Vladimír
Published: May 2010

Temperature dependence of saturated vapour pressures of methyl isobutyl ketone, diisobutyl ketone, 1,1-difluorotetrachloroethane, and 1,2-diflurotetrachloethane was measured. A static method was used, and the measurements were carried out in the temperature range of 261 to 353 K and in the pressure range of 0.5-49 kPa.
A simple perturbation method for electrolyte solutions
Authors: Sýs Jan , Malijevský Anatol , Labík Stanislav
Published: May 2010

The first order perturbation expansion of the Helmholtz free energy was used to calculate the thermodynamic properties of aqueous electrolytes. The restricted primitive model was used as the reference system. Its properties were determined using semiempirical formulae consistent with simulated Monte Carlo data. A simple expression with two adjustable parameters was chosen for the perturbation potential. Integral heats of dilution and osmotic coefficients of alkaline halides and tetraalkylamonium bromides were calculated. An excellent agreement with the tabulated data was found up to the concentrations of 2-3mol/dm3.
Permeation and sorption methods for the determination of transport parameters of gases and vapours through flat membranes
Authors: Hodek Jiří , Šípek Milan , Šlechta Oskar
Published: May 2010

New relations were derived for the determination of diffusion coefficients, coefficients of permeability, and sorption coefficients of gases and vapours through flat membranes by means of the permeation and sorption methods. To verify these relations, a polyurethane filled with silicium oxide (Silica) was chosen as a model system. Transport parameters of water vapours at the temperature of 25 °C were determined of this system by the sorption and permeation methods. Both the methods yield practically the same transport parameters especially after evacuating the membrane before the measurement by the permeation technique.
Segmented electrodiffusion probes: Simultaneous measurement of shear rate and normal flow component
Authors: Wein Ondřej , Sobolík Václav
Published: May 2010

The existing theory of direction-sensitive electrodiffusion probes for the wall shear rate measurement is extended by including normal flow effects.
Influence of substituents on electrochemical reduction potentials of benzenediazonium salts
Authors: Janderka Pavel , Cejpek Igor
Published: May 2010

TAST polarography, differential pulse polarography, and cyclic voltammetry on a hanging mercury drop and on a platinum disc were employed to measure the electrochemical reduction potentials of nine para substituted benzenediazonium salts in dimethylformamide. A satisfactory linear correlation was obtained between the potentials of the adsorption prewave and the substituent constants σ+p. The influence of substituents on some structural parameters was studied by using the CNDO/2 method for both a closed and a opened shell.
Theory of segmented electrodiffusion probes: The effect of insulating insertions
Authors: Wein Ondřej , Wichterle Kamil
Published: May 2010

Simple formulae are given for the calculation of limiting diffusion currents to a series of three strip electrodes separated by insulating insertions.
Coordination compounds of nickel and cobalt with the Schiff base derived from thiosemicarbazide and diacetylmonooxime
Authors: Březina František , Šindelář Zdeněk , Pastorek Richard , Lasovský Jan
Published: May 2010

Coordination compounds with the compositions [Ni(H2TSD)2]Cl2, [Co(H2TSD)2]Cl2, [NiH2O(TSD)], [CoH2O(TSD)] and [Co(TSD)(HTSD)].2H2O were prepared, where H2TSD = HON=C(CH3)C(CH3)=N.NH.CS.NH2. Cyclic voltammetry indicated that [NiH2O(TSD)] can be oxidized and reaction of this compound with bromine yielded the nickel compound with the composition [Ni(TSD)Br]. The properties of the ligand that make it useful for stabilizing the higher oxidation states of nickel are discussed.
Injury-prevention priorities according to playing position in professional rugby union players
Authors: Brooks J H M , Kemp S P T
Published: May 2010

Objective

To examine the match injury profile of professional rugby union players by individual playing position.

Design

4-season prospective cohort design.

Setting

14 English Premiership clubs.

Participants

899 professional players.

Main outcome measure

Incidence of match injury (recorded as the number of injuries/1000 player-hours of match exposure), severity of injury (recorded as the number of days of absence) and days of absence due to injury per 1000 player-hours of match exposure.

Assessment of risk factors

Injury diagnosis and individual playing position during a match.

Results

2484 injuries were reported. While there were no significant differences in the total days of absence as a result of injury between different positions in the forwards and the backs, there were a number of significant differences in injury profile for players in individual playing positions. Although three common body locations caused a high proportion of days of absence due to match injury for forwards (shoulder, knee, ankle/heel) and backs (shoulder, hamstring, knee), there were significant differences in injury profile between individual positions.

Conclusions

The results clearly demonstrate the need for individual position-specific injury-prevention programmes in rugby union. When devising such programmes, a player's previous injury history should also be taken into account.
Reliability and validity testing of a single-item physical activity measure
Authors: Milton K , Bull F C , Bauman A
Published: May 2010

Objective

To develop and test a new single-item physical activity screening tool, suitable for assessing respondents' eligibility for behaviour change interventions.

Design

Two single-item assessment tools were developed, one using a “past week” recall period, the other using a “past month” recall period. A quota sampling system was used to recruit 480 adults from across England, Scotland and Wales. Half the sample completed the past-week question and half completed the past-month version. Test–retest reliability was assessed over a 2- to 5-day period. Concurrent validity was assessed using the Global Physical Activity Questionnaire and the UK Active People Survey. All surveys were completed via telephone interviews.

Results

Both versions of the single-item instrument demonstrated strong reproducibility (r=0.72–0.82), using Spearman's rank correlation coefficients. The past-week recall question showed strong agreement in the classification of respondents meeting the current physical activity recommendation (kappa=0.63, 95% CI 0.54 to 0.72).Concurrent validity over the past week compared to the Global Physical Activity Questionnaire was modest (r=0.53) and slightly weaker for the past month compared to the Active People Survey (r=0.33–0.48).

Conclusion

Both versions of the new single-item measure performed as well as other short physical activity tools in terms of reliability and concurrent validity. Criterion validity testing of the single-item measure is recommended to establish its ability to assess objectively measured physical activity levels. In addition, further research to assess the responsiveness of the single-item measure in detecting changes in physical activity will inform its usefulness in programme evaluation.
The effects of fasting on metabolism and performance
Authors: Maughan R J , Fallah J , Coyle E F
Published: May 2010

An overnight fast of 8–10 h is normal for most people. Fasting is characterised by a coordinated set of metabolic changes designed to spare carbohydrate and increase reliance on fat as a substrate for energy supply. As well as sparing the limited endogenous carbohydrate, and increased rate of gluconeogenesis from amino acids, glycerol and ketone bodies help maintain the supply of carbohydrate. Many individuals undergo periodic fasts for health, religious or cultural reasons. Ramadan fasting, involving 1 month of abstention from food and fluid intake during daylight hours, is practised by a large part of the world population. This period involves a shift in the pattern of intake from daytime to the hours of darkness. There seems to be little effect on overall daily dietary intake and only small metabolic effects, but there may be implications for both physical and cognitive function. The limited evidence suggests that effects of Ramadan-style fasting on exercise performance are generally small. This needs to be balanced, however, against the observation that small differences in performance are critical in determining the outcomes of sporting events. Studies involving challenging sporting events (prolonged sustained or intermittent high-intensity events, hot and humid environments) are needed. Increases in subjective sensations of fatigue may be the result of loss of sleep or disruption of normal sleep patterns. Modifications to the competition timetable may minimise or even eliminate any effect on performance in sport, but there may be negative effects on performance in some events.
Ingestion of sodium citrate suppresses aldosterone level in blood at rest and during exercise
Authors: Ööpik Vahur , Timpmann Saima , Hackney Anthony C. , Kadak Kadri , Medijainen Luule , Karelson Kalle
Published: May 2010

The purpose of this study was to determine if the ingestion of sodium citrate (CIT) alters blood levels of fluid and electrolyte regulatory hormones at rest and during exercise. Using a randomized, double-blinded, crossover design, 13 young, male well-trained runners performed continuous incremental running tests to volitional exhaustion on a treadmill 2 h after ingestion of 0.5 g·kg–1 body mass of CIT or placebo (PLC) in 1000 mL of solution. These trials were separated by 2 weeks. Baseline (before ingestion) aldosterone concentration did not differ between the 2 trials; however, it was 36.5% (p = 0.003) lower in the CIT trial compared with the PLC trial before the running test (i.e., after ingestion). The extent of the running-induced increase in aldosterone was 33% (p = 0.009) smaller in the CIT trial. There were no between-trial differences in the levels of adrenocorticotropic hormone, N-terminal pro-B-type natriuretic peptide, or renin activity at any stage of the study. However, a greater relative increase in plasma volume (mean ± SD, 6.41% ± 3.78% vs. 4.08% ± 3.33%; p = 0.042) was observed after administering the CIT compared with the PLC drink. Serum Na+ concentration increased (by 3.1 ± 1.2 mmol·L–1; p < 0.0001) after ingestion of the CIT but not the PLC drink. A higher Na+ level was observed in the CIT trial than in the PLC trial (142.4 ± 1.6 vs. 139.3 ± 1.4 mmol·L–1, p = 0.00001) after completion of the run. In conclusion, pre-exercise ingestion of CIT induces a decrease in serum aldosterone concentration in the resting condition and a blunting of the aldosterone response during incremental running exercise to volitional exhaustion. The observed effect of CIT on the serum aldosterone level may be mediated by an acute increase in plasma volume and serum Na+ concentration alterations.