bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and spectral properties of substituted 1,4-dihydropyridines and 1,4,5,6,7,8-hexahydroquinolines
Authors: Čupka Pavol , Bella Juraj , Martvoň Augustin
Published: June 2010

Cyclocondensation of 5-nitrophenyl-2-furaldehydes or 5-nitrophenyl-2-thiophenecarbaldehydes with acetoacetates and ammonia in organic solvents afforded 1,4-dihydropyridine derivatives, with 3-aminocrotonates and dimedone the former yielded 1,4,5,6,7,8-hexahydroquinoline derivatives. Relation between the structure and spectral properties is discussed.
Side-products of acylation of 1-acetoxy-2-phenoxyethane with phenylacetyl chloride
Authors: Lukáč Ivan , Kačuráková Marta , Malík Ľubomír
Published: June 2010

Acylation of 1-acetoxy-2-phenoxyethane with phenylacetyl chloride in the presence of anhydrous aluminium chloride or tin tetrachloride afforded 1-acetoxy-2-(4-phenylacetylphenoxy)ethane (I) as the principal product. In the presence of aluminium chloride 1-[4-(2-acetoxyethoxyphenyl)]-1-chloro-2-phenylethene (II), 1,1-di-[4-(2-acetoxyethoxyphenyl)]-2-phenylethene (III) and 1-[4-(2-hydroxyethoxyphenyl)]-1-chloro-2-phenylethene (IV) were isolated as side-products whereas in the tin tetrachloride-catalyzed reaction only III was detected.
Conversion of thioacetamides, acetamides, and acetonitriles into trimethinium salts under Vilsmeier conditions
Authors: Liebscher Jürgen , Knoll Alexander , Hartmann Horst , Anders Sabine
Published: June 2010

Thioacetamides and N-(3-aminothioacryloyl)formamidines can be transformed to trimethinium salts by the reaction with formamide chlorides. The same products are formed by a modified Vilsmeier-Haack-Arnold reaction of acetamides or acetonitriles. The latter transformations can also be performed in two steps by the isolation of intermediate 2-aza-3-chlorpentamethinium salts.
Esters of arylpropionic acids with 1,2:5,6-di-O-isopropylidene- and 1,2-O-isopropylidene-α-D-glucofuranose
Authors: Svoboda Jiří , Čapek Karel , Paleček Jaroslav
Published: June 2010

On fractional crystallization of 3-O-(2-(2-fluoro-4-biphenylyl)propionyl)-, 3-O-(2-(4-isobutylphenyl)propionyl)- and 3-O-(2-(6-methoxy-2-naphthyl)propionyl)-1,2 :5,6-di-O-isopropylidene-α-D-glucofuranoses V-VII optically pure R-diastereoisomers were isolated. The derivatives of 1,2-O-isopropylidene-α-D-glucofuranose obtained on partial deacetylation of esters V-VII were separated chromatographically to R and S-diastereoisomers. Their hydrolysis or transesterification afforded optically pure arylpropionic acids or their methyl esters, respectively. Kinetic resolution of the acids gives rise to esters V-VII enriched in R-diastereoisomer.
Occurrence of magnoflorine and corytuberine in some wild or cultivated plants of Czechoslovakia
Authors: Slavík Jiří , Bochořáková Jitka , Slavíková Leonora
Published: June 2010

Magnoflorine was isolated for the first time from Adonis vernalis L., Clematis recta L., and Epimedium versicolor MORR., further also from Aquilegia sp., Caltha palustris L., Isopyrum thalictroides L., and Aristolochia clematitis L. It was detected in Adonis aestivalis L., Clematis vitalba L., Consolida regalis GRAY, and Helleborus viridis L. Corytuberine was isolated for the first time from Caltha palustris L. and detected in small amounts in Adonis vernalis, A. aestivalis, Aquilegia sp., Consolida regalis, Clematis recta, Eranthis hiemalis L., Helleborus foetidus L., H. niger L., H. viridis, Isopyrum thalictroides, and Aristolochia clematitis. From Consolida regalis a quaternary alkaloid (iodide C22H34NO2I) was isolated as the main component, probably of diterpenoid type. A small amount of coptisine was isolated from Isopyrum thalictroides and Aquilegia sp.
Transfer of 1,1'-dialkyl-4,4'-bipyridinium dication (viologen) across the water-dichloroethane and water-nitrobenzene interfaces
Authors: Hanzlík Josef , Samec Zdeněk
Published: June 2010

Transfer of viologen dications R2V2+ (R = methyl, ethyl, propyl, butyl, pentyl, heptyl or benzyl) across the water-1,2-dichloroethane and water-nitrobenzene interfaces has been studied by cyclic voltammetry. Effects of the changes in the viologen structure and in the composition of solutions of both phases on the voltammetric behaviour have been inspected. Ion association, in particular that occuring in the organic phase, has a considerable influence on the viologen dication transfer and plays the key role in the proposed charge transfer mechanism. From the conductivity measurements the association constants for viologen tetraphenylborates in nitrobenzene have been evaluated. From the voltammetric measurements the Gibbs energies of transfer of viologen dications across the water-nitrobenzene interface have been determined.
The polarographic and voltammetric determination of congo red
Authors: Barek Jiří , Tietzová Barbara , Zima Jiří
Published: June 2010

The polarographic reduction of the bisazodye congo red has been studied, a mechanism was proposed for this process and optimal conditions were found for determination of this substance by TAST polarography and differential pulse polarography at a dropping mercury electrode and using fast scan differential pulse voltammetry and voltammetry with linearly increasing voltage at a hanging mercury drop electrode. The detection limit for the latter two techniques is about 10-8 mol l-1; a further decrease in the value can be attained by prior accumulation of the determined substance by adsorption on the surface of the working electrode.
A spectrophotometric study of the complexation equilibria and the determination of nickel(II) with 4-(2-pyridylazo)resorcinol, 4-(2-thiazolylazo)resorcinol, and 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol
Authors: Langová Marie , Šimek Zdeněk , Chromá Jitka , Sommer Lumír
Published: June 2010

The complexation equilibria of Ni(II) with 4-(2-pyridylazo)resorcinol (PAR) and 4-(2-thiazolylazo)resorcinol (TAR) in 30 vol.% ethanol and with 2-(5-bromo-2-pyridylazo)-5-(diethylamino)phenol (BrPADAP) in 10 vol.% ethanol containing 0·1% BRIJ-35 tenside were studied spectrophotometrically. The absorbance data were processed by the SPEFO 8, HALTAFALL SPEFO and SQUAD-G programs. The working procedures for the determination of Ni(II) with the reagents in pure solutions were optimized and statistically evaluated, and PAR was applied to the determination of Ni(II) in drinking water.
The crystal and molecular structure of cobalt(III) sym-fac-N-(2-aminoethyl)-1,3-diaminopropane-(S)-aspartate perchlorate, sym-fac-[Co-(aepn)(S)-Asp]ClO4
Authors: Kratochvíl Bohumil , Ondráček Jan , Ondráčková Jana , Soldánová Jiřina , Jursík František , Hájek Bohumil
Published: June 2010

The crystal and molecular structure of sym-fac-[Co-(aepn) (S)-Asp]ClO4 was solved by the heavy atom method. The positions of the nonhydrogen atoms and their anisotropic temperature factors were refined. On the basis of 1 514 observed reflection intensities, a final reliability factor value of R = 0.096 was obtained (wR = 0.101). The substance crystallizes in the orthorhombic system in the P212121 space group. The elementary cell contains four formula units and has dimensions of a = 704.0(6), b = 939.4(7), c = 2 369(2) pm. The secondary nitrogen atom of the triamine has S confuguration. The five-membered ring has the λ conformation and the six-membered ring the flattened chair conformation. Selected structural parameters indicate that facial coordination of N-2-aminoethyl-1,3-diaminopropane leads to decreased strain in the coordinated, slightly deformed octahedron than meridional coordination and also that the chelate rings of the triamine are conformationally dependent. The bond lengths and angles of the part formed by (S)-aspartic acid agree with the corresponding values in [Co-((S)-Asp)2]-.
The synthesis and reactions of trisubstituted N-(X-2-benzothiazolyl)formamidines
Authors: Lácová Margita , Nga Nguyen Thi
Published: June 2010

The modified Vilsmeier-Haack reagent ANC(O)H-ClSO2C6H5 (A = (CH3)2, (C2H5)2, (CH2)5, CH2CH2OCH2CH2) reacts with 2-amino-X-benzothiazole in pyridine and ether to give three types of products in high yields depending on the character of substituents A and X. Isolated were: N,N-dialkyl-N'-(X-2-benzothiazolyl)formamidines, N,N'-bis(X-2-benzothiazolyl)formamidines, and N,N-dialkyl-N',N´´-bis(X-2-benzothiazolyl)triaminomethanes. Investigated were the conditions and reaction products of N,N-dialkyl-N',N´´-bis(X-2-benzothiazolyl)triaminomethanes with phenylethanoyl, phenoxyethanoyl, 4-chlorophenoxyethanoyl, and N-phthalimidoethanoyl chlorides either in ether or in pyridine. Mutual transformations of the individual products are described.
Preparation of 3β-hydroxy-21,26,27-trinorcholesta-5,23-dien-25→22-olide and 3β-hydroxy-20-(2-furyl)-21-nor-5-pregnene derivatives
Authors: Pouzar Vladimír , Černý Ivan , Drašar Pavel , Vašíčková Soňa , Havel Miroslav
Published: June 2010

A mixture of 22R- and 22S-isomers of 3β-methoxymethoxy-21,26,27-trinorcholesta-5,23-dien-25→22-olide (IX) was prepared from ester I by two synthetic pathways. Lactone IX was converted into hemisuccinate XII via the intermediates X and XI. The isomer ratio in compounds IX-XII was determined by 1H NMR and CD spectra. Lactone IX was converted into 20-(2-furyl)-3β-methoxymethoxy-21-nor-5-pregnene (XIII) and further, via intermediates XIV and XV, to the β-D-glucoside XVI.
4-Substituted 1-(1-(2-(arylthio)-5-halogenophenyl)ethyl)piperazines; Synthesis and biological screening
Authors: Valenta Vladimír , Holubek Jiří , Protiva Miroslav
Published: June 2010

Reactions of 2,5-dichloroacetophenone and 2,5-dibromoacetophenone with a series of thiophenols gave the 2-(arylthio)-5-halogenoacetophenones VII and VIII which were reduced with sodium borohydride in ethanol to the secondary alcohols IX and X. Treatment with thionyl chloride afforded the chloro compounds XI and XII which were transformed by substitution reactions with correspondingly monosubstituted piperazines by two methods to the title compounds I-V. Their salts (maleates and hydrochlorides) showed in addition to antitussic activity some anthelmintic effects towards a series of the helminth species.
Ratio of lyate ions activities in two-components protogenic solvents
Authors: Mollin Jiří , Pavelek Zdeněk , Kašpárek František
Published: June 2010

Kinetic method for the evaluation of lyate ions activities in two-component protogenic solvents has been discussed. Spectral methods for the measurement of equilibria between alkoxide and hydroxide ions have been compared. A correlation between dissociation constants of water and of weak organic acids in solvent mixtures has been found. By means of this correlation, ratios of lyate ions activities in water-ethanol and water-2-propanol mixtures have been calculated. These activity ratios, together with the known composition of reaction products, have been used to evaluate the selectivity of the neutral and alkaline solvolysis of phthalic anhydride and benzyl chloride in solvent mixtures quoted above.
A dual site growth model of gallium arsenide epitaxial layers from the gas phase
Authors: Erdös Emerich , Leitner Jindřich , Voňka Petr , Stejskal Josef , Klíma Přemysl
Published: June 2010

For a quantitative description of the epitaxial growth rate of gallium arsenide, a model is proposed including two rate controlling steps. One of these steps is the diffusion of gaseous components between the gas phase and the epitaxial layer surface, and the other step is of chemical nature, i.e. either the surface reaction or adsorption or desorption of one of the gaseous components. In the model considered, an active dual site is involved in the second rate controlling step, and twelve mechanisms are proposed for which the pertinent rate equations are derived. The individual mechanisms differ one from the other not only by the kind of the rate controlling step but also by the occupation of the dual site, viz. in the both direct and reversed direction. The proposed model is confronted with the dependences of the growth rate on partial pressures of components in the feed found by experiment. The results are discussed with regard to the possibility of individual mechanisms and of the model as a whole, and also with respect to their applicability and to the direction of further investigations.
Possibilities of determining the polymodal pore-size distribution from physical adsorption of nitrogen
Authors: Tomanová Dagmar , Schneider Petr
Published: June 2010

It is shown, on the basis of experimentally determined adsorption isotherms of physical adsorption of nitrogen on two- and three-component mixtures of fine grained porous glasses with narrow pore-size distributions, that the polymodal mesopore-size distribution curves can be evaluated in case that the porous sample contains groups of mesopores differing rather significantly in size. The differentiation of groups of pores gets worse with wider pores where the demands on the accuracy of the relative pressure measurement grow stronger.
The height of expansion in bubbling fluidized beds
Authors: Hartman Miloslav , Veselý Václav , Trnka Otakar , Svoboda Karel
Published: June 2010

A theory of bubble growth due to coalescence in gas fluidized beds was employed to predict the bed expansion. Using the semi-empirical correlation of bubble size by Mori and Wen, an equation for the height of expanded beds has been developed and verified by experiment. Predictions of the proposed formula were compared with the predictions of recent bed expansion correlations.
A study of the structure stability of natural natrolite during its long-run heating
Authors: Rykl Drahoš , Pechar František
Published: June 2010

The structure stability of natrolite heated at 310, 350, 400, and 500 °C for a time from 7.5 min to 8 192 h was studied by weight loss measurements, infrared spectroscopic investigation and evaluation of powder X-ray diffraction data. No substantial structure changes other than partial dehydration were observed. The dehydration process is only associated with the formation of structural hydroxide groups and with short-range changes in the crystal structure arrangement.
A new route to copper(II) μ4–oxo complexes Cu4OHal6I4
Authors: Vít Zdeněk
Published: June 2010

A novel procedure is suggested for the preparation of tetranuclear copper(II) μ4–oxo complexes Cu4OHal6L4 with N-heterocycles as ligands, consisting of the oxidation of piperidine or morpholine complexes of copper(I) halides with organic polyhalo compounds in the presence of water. The reaction proceeds readily even at room temperature giving the product in a high yield (up to 88%).
Quasielastic light scattering from poly(styrene)-dibutyl phthalate solutions
Authors: Štěpánek Petr , Koňák Čestmír
Published: June 2010

Temperature and concentration behaviour of the dynamic structure factor of poly(styrene) was measured in a marginal solvent (dibutyl phthalate) by quasielastic light scattering. Both the concentration and temperature dependences of the hydrodynamic radius of the polymer coil and of the hydrodynamic blob size were found to follow the scaling laws predicted by theory. A relation m + b = -1 between exponents m and b for the concentration and temperature dependence of the blob size in semidilute solutions has been derived, and its validity was checked experimentally.
Conformation of dimethylaminoethanol, its methyl ether and of the corresponding trimethylammonium iodides. NMR and vibrational spectra
Authors: Štokr Jan , Schneider Bohdan , Doskočilová Danica , Ševčík Stanislav , Přádný Martin
Published: June 2010

By analysis of fully coupled 13C NMR spectra and of 1H NMR spectra of dimethylaminoethanol, its methyl ether, and of the corresponding trimethylammonium iodides, populations of isomers generated by rotation about the bonds N-CH2, CH2-CH2, and CH2-O in these compounds in solution were determined. By analysis of Raman and infrared spectra of these compounds in the solid and liquid states it was found that in the crystalline state these compounds form structures with parallel N-CH3 and O-CH2 bonds, which are also preferred in the liquid state.
Addition of esters of chloroacetic acids to 1,3-butadiene catalysed by copper complexes
Authors: Vít Zdeněk , Hájek Milan
Published: June 2010

The addition of alkyl trichloro- and dichloroacetates to 1,3-butadiene catalysed by copper complexes has been studied. The reactivity of the chloroacetates increased with increasing number of chlorine atoms in their molecule and with decreasing number of the carbon atoms of the alkyl of their ester group. The addition of trichloroacetates gave the products (1 : 1 adducts) in around 80 percent yields while the less reactive dichloroacetates afforded the adducts in 35% yields. The 1 : 1 adducts were the products of both 1,4- and 1,2-addition, the relative proportion of which depended especially on the type of the ligand of copper complexes.
Synthesis of elastin-like peptides using the liquid phase method
Authors: Younes M. E. , Rahman S. Abdel , Hattaba A.
Published: June 2010

Elastin-like peptides were synthesized by the liquid-phase method using poly(ethylene glycol) monomethyl ether (PEGM) (m.w. 5 000) as solubilizing support which provides an alternative possibility for conformational studies and spectroscopic measurements in solution. The following sequences were synthesized: Boc-Ala-Pro-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM, Boc-Ala-Pro-Gly-Val-Gly-Val-Ala-Pro-Gly-Val-Gly-Val-APEGM.
Spectrocoulometry – a new spectro-electrochemical technique
Authors: Mocák Ján , Németh Michal , Lapkowski Mieczyslaw , Strojek Jerzy W.
Published: June 2010

A spectrocoulometric macrocell with a direct-view optical probe was designed and constructed, where the optical signal is transferred by light-conducting glass or quartz fibres permitting to work at wavelengths above 410 or 300 nm. The method of measurement on the proposed equipment is described; it was tested in the study of the mechanism and kinetics of oxidation of Fe(bipy)32+ ions (bipy = 2,2'-bipyridyl) with the use of potentiostatic coulometric electrolysis with open-circuit relaxation at a suitable time. The primary product of electrolysis, Fe(bipy)33+, undergoes a follow-up hydrolytic reaction with the formation of a binuclear complex. The rate constant of the reaction of the first order involves the contributions, kBi, from all bases present in solution; the corresponding values for H2O, OH-, bipy, and CH3COO- ions at a ionic strength 0·5 mol dm-3 and 25 °C were determined as kOH = (5·0 ± 0·6) . 105 mol-1 dm3 s-1, kbipy = (1·3 ± 0·2) . 10-1 mol-1 dm3 s-1, kAc = (5·8 ± 1·0) . 10-2 mol-1 dm3 s-1, and kH2O is not significant with respect to experimental errors.
Separation of the main components of raw acetonine by normal-phase liquid chromatography
Authors: Vespalcová Milena , Vespalec Radim
Published: June 2010

The separation procedure of raw acetonine, that is unstable at the room temperature, has been worked out. Alumina was used as the stationary phase. The mixture of an aliphatic hydrocarbon with an alcohol saturated with the concentrated aqueous solution of ammonium hydroxide was used as the mobile phase. It has been proved that the result of the analysis at the room temperature was not affected by the spontaneous decomposition of the sample provided that the analysis did not exceed 30 min. Raw acetonine was found to contain ten components, four of which were identified.
Influence of crystallographic orientation on the potential of aluminium during reaction with aqueous NaOH solution
Authors: Miadoková Milica , Šiška Josef
Published: June 2010

In addition to kinetic measurements, the authors followed the potential of three oriented sections of Al monocrystal during its reaction with aqueous NaOH solution. The time dependences showed a shift of the potential to more positive values; the difference between the stationary, Est, and initial, E0, values was dependent on the orientation of the section and was related to its reactivity. Potential oscillations were observed on the (110) crystal face in the concentration region from 2 to 8 mol dm-3 NaOH, and their period and amplitude were measured. The stationary potential was a parabolic function of the reaction rate at concentrations of NaOH from 0 to 5 mol dm-3.
The formation of fluorooxogermanates in alkali metal nitrate melts
Authors: Drátovský Milan , Uchytilová Marcela
Published: June 2010

Attempts were made to isolate fluorooxogermanates, whose formation in nitrate melts was indicated potentiometrically. The stability of fluorooxogermanates in nitrate melts depends on the melt temperature and on the effect of the cation. In addition to the already known compound, K4[Ge2F10O], a new compound, Na2[GeF4O], was also obtained from nitrate melts. In addition, conditions were found for the formation of both the tetragonal and of the hexagonal modification of GeO2 in nitrate melts.
Acryloyloxy and methacryloyloxy derivatives of phenylacetic acid and their polymers
Authors: Hrabák František , Bezděk Milan , Lokaj Jan , Pivcová Hana , Kubánek Vladimír
Published: June 2010

2-Methacryloyloxy-2-phenylacetic acid (I), 2-acryloyloxy-2-phenylacetic acid (II), 4-methacryloyloxyphenylacetic acid (III), and 4-acryloyloxyphenylacetic acid (IV), ethyl 4-methacryloyloxyphenylacetate (V) and ethyl 4-acryloyloxyphenylacetate (VI) were prepared. The new monomers were characterized by their melting points, IR, 1H and 13C NMR spectra; their polymerization was also examined.
Pyrolysis of methylcyclohexane
Authors: Králíková Ulrika , Bajus Martin , Baxa Jozef
Published: June 2010

The kinetics of pyrolysis of methylcyclohexane was investigated from the viewpoint of coke formation in a steel tubular reactor (S/V = 6·65 cm-1) at 0·1 MPa, 700 to 820 °C and residence time 0·01 to 0·24 s. Decomposition of methylcyclohexane proceeds as a first order reaction with a frequency factor 6·31 . 1015 s-1 and activation energy 251·2 kJ mol-1. The course of secondary reactions associated with the formation of coke is discussed. Investigation of coke formation showed a greater tendency of methylcyclohexane to coking in comparison with heptane. A prominent role plays the course of dehydrogenation of cycloalkane radicals up to aromates, this being reflected by the overall conversion of methylcyclohexane, and, on the other hand the thus formed aromates enter the consecutive reactions leading to coke.
Nitriles in organic synthesis: A novel synthesis of 2-thienylbiaryls
Authors: Elagamey Abdel Ghani A. , Sofan Mamdouh A. , Kandeel Zaghloul E. , Elnagdi Mohamed H.
Published: June 2010

A novel synthesis of 2-thienylbiaryls via the reaction of the 2-cyano-3-(2-thienyl)crotononitrile with cinnamonitriles is reported. The same products were also obtained from the reaction of 1,1-dicyano-2-thienyl-4-arylbuta-1,3-dienes with malononitrile or ethyl cyanoacetate.
5'-O-Alkyl-5-fluorouridines: Synthesis and biological activity
Authors: Holý Antonín , König Joachim , Veselý Jiří , Cech Dieter , Votruba Ivan , De Clercq Erik
Published: June 2010

Methyl 2,3-O-isopropylidene-D-ribofuranoside (IV) was alkylated with alkyl halides in the presence of sodium hydride and the products were transformed by acid hydrolysis and glycosylation into methyl 5-O-alkyl-D-ribofuranosides VII. Benzoylation of VII followed by acetolysis afforded 1-O-acetyl-2,3-di-O-benzoyl-5-O-alkyl-D-ribofuranoses IX which on reaction with 2,4-bis(trimethylsilyloxy)pyrimidine in the presence of tin tetrachloride in acetonitrile and subsequent hydrolysis gave 5'-O-alkyl-2',3'-di-O-benzoyluridines XIa-XIe. Methanolysis of compounds XI furnished 5'-O-alkyluridines III. The 5-O-allyl derivative XII was hydroxylated in the presence OsO4 and transformed further to 5'-O-(RS)-(2,3-dihydroxypropyl)uridine (IIIg) and its tetrabenzoate XVI. Compounds XI and XVI on reaction with elemental fluorine in acetic acid afforded benzoyl derivatives of 5'-O-alkyl-5-fluorouridines XVIIa-XVIIe and XIX which were methanolyzed to give 5'-O-alkyl-5-fluorouridines II. This procedure afforded 5'-O-methyl (IIa), ethyl (IIb), n-butyl (IIc), n-hexyl (IId), n-octyl (IIe), and (RS)-(2,3-dihydroxypropyl) (IIf) derivatives of 5-fluorouridine. None of the compounds II exhibited antibacterial effect on Escherichia coli B or antiviral activity against HSV-1, HSV-2, vaccinia virus or vesicular stomatitis viruses. Compounds IIc,d,e suppressed the growth of L 1210 mice leukemic cells at concentrations of 10-5 to 10-6 mol l-1; the 5'-O-n-butyl derivative IIc has the highest activity (ID50 2·8 μmol l-1) but does not prolong the life span of L 1210 leukemia bearing mice following repeated daily doses of 80 mg/kg.
Role of amino acid residues in chromogenic substrates cleaved by pancreatic elastase
Authors: Kasafírek Evžen , Frič Přemysl , Slabý Jan
Published: June 2010

Anionic chromogenic substrates, 3-carboxypropionyl tripeptide p-nitroanilides modified with glycine, β-alanine, alanine, leucine and proline in positions P1, P2, and P3 were synthesized. The substrates were digested with pancreatic elastase and the values of Km, kcat, and kcat/Km were determined. Alanine plays a decisive role in position P1, substrates with glycine or β-alanine in this position are not cleaved. The substitution in P2 is dominant for proline; next follow alanine, leucine, and glycine. The substitution in P3 is the least specific one.
Alkaloids of Papaver nudicaule SUBSP. xanthopetalum (TRAUTV.) FEDDE and P. nudicaule SUBSP. album (REGEL) FEDDE from the section Scapiflora REICHB.
Authors: Věžník František , Táborská Eva , Bochořáková Hana , Tureček František , Hanuš Vladimír , Slavík Jiří
Published: June 2010

The alkaloidal composition in the two title taxa differs only quantitatively. Both contain amurine as the main alkaloid. P. nudicaule ssp. xanthopetalum contains muramine, protopine and alkaloid PN1 (probably identical with (±)-nudaurine (Ia)) as dominant alkaloids; further were isolated amurensine, epialpinine, cryptopine, mecambridine and alpinigenine. Allocryptopine, papaverrubines A, B, D and G, palmatine and coptisine were detected chromatographically. The quaternary alkaloid fraction afforded cis-N-methylstylopinium hydroxide (as the iodide II) which was isolated for the first time from P. nudicaule. In P. nudicaule ssp. album the alkaloid PN1, epialpinine, amurensine and muramine represented the dominant alkaloids, accompanied with mecambridine, protopine, cryptopine, allocryptopine and alpinigenine. Among the quaternary alkaloids N-methylstylopinium hydroxide was found.
The principle of ionic additivity and interaction parameters for the systems water-salt
Authors: Horsák Ivan , Sláma Ivo
Published: June 2010

A theoretical approach to the evaluation of water-salt phase diagrams has been developed which leads to the concentration dependence of the activity coefficient of water. Literature data for water-alkali halide systems were used to evaluate these dependences in an empirical manner and by using an equation derived from the lattice model of electrolytes. As an alternative, a joint evaluation of all the data was made by invoking the applicability of the principle of ionic additivity to the interaction parameters. In this way, an economical prototype of a data bank of interaction parameters of electrolyte systems has been established. The approach adopted represents a significant step forward in the generalization and prediction of solid-liquid phase equilibria in the systems water-salt.
Modelling of mass transport and chemical reaction in a diaphragm
Authors: Schleiff Martin , Lefeld Günther , Matschiner Hermann , Špalek Otomar
Published: June 2010

A mathematical model was proposed for the transport of ions in a diaphragm separating an acidic and an alkaline electrolyte. Besides an approximate analytical solution, a more exact numerical one was presented. The model permits the calculation of the position of the neutralization zone in the diaphragm, rates of transport of ions, and potential in the diaphragm. The dependence of the position of the neutralization zone on the composition of both electrolytes and on the current density was calculated for two technically important cases.
An advantageous synthesis of S-(2-propenyl) N-acylmonothiocarbamates by [3,3]-sigmatropic rearrangement of O-(2-propenyl) N-acylmonothiocarbamates
Authors: Kutschy Peter , Dzurilla Milan , Koščík Dušan , Kristian Pavol
Published: June 2010

Reaction of acetyl, benzoyl, 2-chlorobenzoyl, 3-phenylpropenoyl, 2-naphthoyl, and 3-chloro-2-benzo[b]thienocarbonyl isothiocyanate with 2-propen-1-ol afforded the corresponding O-(2-propenyl) N-acylmonothiocarbamates which underwent [3,3]-sigmatropic rearrangement on heating in boiling benzene. The reaction represents a simple method for preparation of S-(2-propenyl) N-acylmonothiocarbamates in yields ranging from 50% to 98%.
Fluorinated tricyclic neuroleptics with prolonged action: derivatives and analogues of 2-(4-(7-fluoro-2-isopropyl-10,11-dihydrodibenzo[b,f]thiepin-11-yl)-piperazine-1-yl)ethanol
Authors: Protiva Miroslav , Jílek Jiří , Rajšner Miroslav , Šindelář Karel , Bártl Václav , Ryska Miroslav , Koruna Ivan , Holubek Jiří , Svátek Emil , Metyšová Jiřina , Dlabač Antonín , Pomykáček Josef , Mikšík František
Published: June 2010

The preparation of 4-fluoro-2-nitrobenzonitrile (V), an intermediate in the synthesis of the title compound I, from 4-fluoro-2-nitroaniline via 5-fluoro-2-iodonitrobenzene (VII) was elaborated. Syntheses of 1,1,1,3,3,3-hexadeutero-2-propyl (XX) and 1,3,4-trideutero (XXVIII) analogues of compound I from hexadeuteroacetone, and pentadeuterobromobenzene, respectively, were carried out. Compound I was esterified with acetic anhydride, decanoic acid and 3,4,5-trimethoxybenzoyl chloride to give the esters II-IV. Acylation of compound XXX with acetyl chloride, 4-fluorophenoxyacetyl chloride and (4-fluorophenylthio)acetyl chloride and the following reduction of the amides with lithium aluminium hydride gave compounds XXXII, XXXIX and XL. Substitution reactions of 11-chloro-7-fluoro-2-isopropyl-10,11-dihydrodibenzo[b,f]thiepin with the corresponding N-monosubstituted piperazines resulted in compounds XXXIII-XXXV, XXXVII, XXXVIII, XLI and XLII. Alkylation of XXX with 2-(2-chloroethyl)-1,3-dioxolane afforded compound XXXVI. Pharmacological testing of the new compounds, derivatives and analogues of the neuroleptic agent isofloxythepin (I), for discoordinating and cataleptic activities, showed especially for compounds II, XXXIV and XXXVI very intensive and long-lasting effects. The decanoate III has properties of a depot neuroleptic agent.
1-(4-Cyclopentylphenyl)piperazine and its 4-substituted derivatives; Synthesis and biological screening
Authors: Vejdělek Zdeněk , Protiva Miroslav
Published: June 2010

Heating the hydrochlorides of 4-cyclopentylaniline and diethanolamine to 250 °C gave 1-(4-cyclopentylphenyl)piperazine (I). Acylation of I with ethyl formate and the corresponding acyl chlorides gave the amides II, VI, and VII which were reduced with lithium aluminium hydride to the piperazines III, VIII, and IX. Treatment of I with benzyl chloride and with 4-chloro-1-(4-fluorophenyl)butan-1-one under different conditions led to compounds IX and XI. Addition reaction of I to 1,2-epoxybutane resulted in the amino alcohol V. The products showed marginal tranquillizing activity (especially compound VIII), some antimicrobial activity in vitro and some anthelmintic activity.
Three cyclohexapeptides modelling the oxytocin ring moiety: Synthesis and circular dichroism
Authors: Hlaváček Jan , Frič Ivo , Maloň Petr , Jošt Karel , Bláha Karel
Published: June 2010

A series of cyclic disulfides cysteinyl-triglycyl-asparaginyl-cysteine (Ib), cysteinyl-diglycyl-glutaminyl-asparaginyl-cysteine (Ic), and cysteinyl-glycyl-isoleucyl-glutaminyl-asparaginyl-cysteine (Id) has been prepared. The effect of gradual attachment of side chains to the ring on the peptide backbone and the disulfide group conformation has been studied using circular dichroism. Introduction of side chains reduces substantially the conformational mobility of the backbone , but not enough to let any conformational β-turn type predominate (in polar solvents). Conformation of the disulfide group is essentially independent of the peptide moiety of the molecule and is influenced by specific solvation.
Effect of modification of certain amino acid residues on enzyme activity of D-3-hydroxybutyrate dehydrogenase from bacterium Paracoccus denitrificans
Authors: Kovář Jan , Matysková Ivana
Published: June 2010

We examined the effect of several modifying reagents on the activity of the title enzyme. The results show that one histidine residue participates in the interaction of the enzyme with the substrate; one cysteine residue binds near to the nicotine amide moiety of the coenzyme molecule and its role is to induce conformational changes leading to the formation of enzyme aggregates with an increased catalytic power. The enzyme does not contain essential tyrosine and tryptophan residues. The results of the experiments with the modification of additional amino acid residues permit us to make preliminary conclusions only based on the knowledge of the protective effect of the individual ligands: One arginine residue may be involved in the binding of the coenzyme, the residues of lysine and serine may be localized in the substrate binding site.
Quantum chemical study of phenylcarbamates possessing local anaesthetic activity. Effect of hydration on stable conformations of 1-[2-(2-methoxyphenylcarbamoyloxy)ethyl]piperidine and its cation
Authors: Remko Milan , Sekerka Ivan
Published: June 2010

The PCILO quantum chemical method was applied to the study of 1-[2-(2-methoxyphenylcarbamoyloxy)ethyl]piperidine (B), its cation (BH+), and hydrofluoride (BHF). For B and BH+, their principal hydration sites were established. Conformation maps of the hydrated molecules were plotted based on the “supermolecule” concept and compared with those of the isolated species. As compared to the nonhydrated molecules, the hydrated B and BH+ have a considerably smaller tendency to assume one preferred conformation. The preferred conformation of isolated molecule of BHF as obtained by the PCILO calculation agrees well with crystal structure data of the structurally related heptacaine hydrochloride.
Pulse dynamic measurements of oxygen chemisorption on sulphided Co-Mo/Al2O3 catalyst – Effect of experimental conditions
Authors: Zahradníková Hana , Beránek Ludvík
Published: June 2010

The effect of temperature and time regime of individual steps of the methodic procedure (i.e. catalyst drying, sulphidation, purification of the sulphided surface by inert gas, and chemisorption) on pulse dynamic measurements of oxygen chemisorption of commercial sulphided Co-Mo/Al2O3 catalyst have been studied. The strongest effect was exerted by the chemisorption temperature and by the temperature and time of purification of the surface of sulphided catalyst. Optimum experimental conditions for testing catalysts of this type by the described chemisorption method are proposed.
Kinetics of acid-catalyzed cyclization of substituted hydantoinamides to substituted hydantoins
Authors: Kaválek Jaromír , Macháček Vladimír , Svobodová Gabriela , Štěrba Vojeslav
Published: June 2010

The kinetics of acid-catalyzed cyclization of the hydantoinamides type R3-N(5)H-CO-N(3)R2-CH2-CO-N(1)HR1 (R1, R2, R3 = H and/or CH3) has been studied in 0·5 to 5 mol l-1 hydrochloric acid. The cyclization rate is limited by the rate of the attack of nitrogen atom N(5) on the carbon atom of the protonated amide group. The dissociation constants of the protonated hydantoinamides and rate constants of their cyclizations have been determined. Replacement of hydrogen atom by methyl group at the N(5) nitrogen atom accelerates the cyclization about two times., the same substitution at N(3) accelerates about 50x, whereas at N(1) it results in a 300 fold retardation. With the hydantoinamides having R3 = CH3, the cyclization rate of the protonated hydantoinamide increases with increasing concentration of hydrochloric acid, whereas with the other derivatives this value is independent of the acid concentration.
Model reactions for the study of hydrogenation and acidic activity of palladium catalysts
Authors: Červený Libor , Du Nguyen Thi , Paseka Ivo
Published: June 2010

Palladium catalysts have been used to study the hydrogenation of 1-phenyl-2-butene-1-ol which is accompanied by several side reactions considered to be acid-catalysed. Another model reaction studied was dehydration and subsequent hydrogenation or hydrogenolysis of 1-phenyl-1,3-propanediol to 3-phenyl-1-propanol, accompanied by formation of propylbenzene. The dehydration and propylbenzene formation can be again classified as acid-catalysed reactions. Another one is methanolysis of styrene oxide taking place under conditions of liquid phase hydrogenation due to the acid properties of Pd-H systems. Hydrogenation activity of Pd catalysts was tested by hydrogenation of cyclohexene. Sixteen Pd catalysts on different supports and with different content of active component were used, their activity and selectivity was determined and the effect of variable parameters in the synthesis of these catalysts on the activity and selectivity is discussed.
2',3'-O-Carbonyl derivatives of 6-azauridine in the synthesis of its 5-substituted and 5'-deoxy derivatives
Authors: Drašar Pavel , Beránek Jiří
Published: June 2010

Preparation of 2',3'-O-carbonyl derivatives of 5'-deoxy-6-azauridine and 6-azauridine using 1,1'-carbonyldiimidazole has been elaborated. 5'-Chloro and 5'-bromo derivatives were prepared by treatment of the 5'-O-mesyl derivative with quaternary ammonium halides, 5'-chloro derivatives also by direct halogenation with thionyl chloride in hexamethylphosphortriamide or with tetrachloromethane, triphenyl phosphine, and dimethylformamide. Derivatives of 5'-bromo-6-azauridine were reduced with tributyltin hydride to 5'-deoxy-6-azauridine compounds. 6-Azauridine 2',3'-carbonate (IVa) and its 5'-derivatives IVc and IVe on treatment with imidazole in dimethylformamide afforded 2,2'-anhydronucleosides IIIa-IIIc. The 2,2'-anhydro-5'-deoxy compound IIIc underwent alkaline hydrolysis to 5'-deoxy-1-β-D-arabino-pentofuranosyl-6-azauracil (VIa). Treatment of 2,2'-anhydro-5'-deoxy-5'-chloro derivative IIIb with hydrogen chloride led to 2',5'-dichloro derivative If.
Acylated thioamides and related compounds as potential antituberculotics
Authors: Mollin Jiří , Polášková Kateřina , Odlerová Želimíra , Bekárek Vojtěch
Published: June 2010

Some N-acylthioamides, thiobenzoylthioureas, and thiobenzoylureas were synthesized. The substances prepared were tested for their in vitro antimycobacterial activity. The structure of thiobenzoylureas was studied by synthetic and spectral methods.
Potential neuroleptics of the orthopramide series; Synthesis of N-substituted 5-(aminosulfonyl)-2-methoxybenzamides
Authors: Valenta Vladimír , Protiva Miroslav
Published: June 2010

The mixed anhydride of 5-(aminosulfonyl)-2-methoxybenzoic acid (VII) and monoethyl carbonate reacted with benzylamine, 1-methylpiperazine, and 1-benzylpiperazine to give the 5-(aminosulfonyl)-2-methoxybenzamides II, IV, and V. Heating the ethyl ester X with 4-amino-1-methyl-piperidine resulted in the amide III. Reaction of 5-(chlorosulfonyl)-2-methoxybenzoyl chloride (XI) with 1-benzylpiperazine afforded 5-(4-benzylpiperazinosulfonyl)-2-methoxybenzoic acid 4-benzylpiperazide (VI). Compounds II-VI are analogues of the antidopaminergic and antiemetic agent sulpiride (I) but only benzylpiperazides V and VI showed indications of psychotropic activity of the neuroleptic type.
Effect of heterocyclic compounds and 2-mercaptoethanol on rape alcohol dehydrogenase
Authors: Stiborová Marie , Leblová Sylva
Published: June 2010

Rape alcohol dehydrogenase (ADH) is inhibited by heterocyclic compounds with a five- to six-membered ring (imidazole, pyrazole, 4-methylpyrazole, 3-methylpyrazole, pyridine, nicotine amide) and by o-phenanthroline, a heterocyclic, polycyclic compound. Pyrazole and its derivatives, imidazole and pyridine, are competitive inhibitors with respect to ethanol. Nicotine amide and o-phenanthroline behave as mixed inhibitors (competitive – noncompetitive) with respect to the substrate. The addition of Zn2+-ions to the reaction medium interferes with the competition by o-phenanthroline. 4-Methylpyrazole and pyrazole are the strongest inhibitors of rape ADH. 2-Mercaptoethanol is an inhibitor of rape ADH which competes with ethanol and the coenzyme. The reversible inhibition by mercaptoethanol changes into the irreversible inactivation of the enzyme. The binding of inhibitors to the zinc atom present in the molecule of rape ADH and the localization of the metal in the enzyme protein have been studied.
Theory of direction sensitive probes for electrodiffusion measurement of wall velocity gradients
Authors: Wein Ondřej , Sobolík Václav
Published: June 2010

Theory of segmented circular electrodes for electrodiffusion measurements is developed in the diffusion layer approximation. A fast subroutine is given for handling the data supplied by three-segment circular electrode.
Reactions of macroions with ester and carboxylic groups of polymers
Authors: Kučera Miloslav , Kimmer Dušan , Majerová Karla , Majer Josef
Published: June 2010

In the reaction of dianions with poly(methyl methacrylate), only an insignificant amount of insoluble crosslinked product is obtained. If, however, the concentration of grafting dianions approaches that of ester groups, the amount of poly(methyl methacrylate) which may thus be crosslinked becomes quite significant. Dications, too, can bring about crosslinking of only an insignificant number of poly(methyl methacrylate) chains. Carboxylic groups in poly(acrylic acid) react with dianions and dications in an anhydrous medium similarly to ester groups. On the other hand, in the presence of a cocatalytic amount of water dications are more readily bound to carboxylic groups, forming a covalent bond. The relatively highest efficiency was observed in the bond formation between dication and the poly[styrene-alt-(maleic anhydride)], both in an anhydrous medium and in the presence of H2O.
Kinetics and mechanism of acid catalyzed decomposition of substituted 1,3-diphenyltriazenes
Authors: Svoboda Petr , Pytela Oldřich , Večeřa Miroslav
Published: June 2010

The kinetics of acid catalyzed decomposition of 3-substituted and 1,3-disubstituted 1,3-diphenyl-3-methyltriazenes have been studied in 40% aqueous ethanolic buffers at 25 °C. The reaction constant for substitution of the phenyl ring at the 3 position of the triazene chain has been determined and the reaction constants of the protonation and bond splitting between the nitrogen atoms 2 and 3 have been estimated. By the covariance analysis it has been found that the standard constants of the Hammett relation are better than the constants determined in the media of organic solvents. Also estimated were the values of the slope β1g of the linear relation between the rate constants and the equilibrium between the diazonium salt and diazotate. The A-SE2 mechanism is suggested as probable, the bond between nitrogen atoms of triazene chain being more than half split in the transition state and the nitrogen-proton bond formation being more advanced than the nitrogen-nitrogen bond splitting.
A new method for preparation of 1-(4-substituted phenyl)-6-phenyl-2-thiouracils via cyclization of N-(4-substituted phenyl)-N'-3-phenylpropenoylthioureas and Dimroth rearrangement of 2-(4-substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones
Authors: Dzurilla Milan , Kutschy Peter , Koščík Dušan
Published: June 2010

N-(4-Substituted phenyl)-N'-3-phenylpropenoylthioureas treated with lithium hydride afforded 1-(4-substituted phenyl)-6-phenyl-2-thiouracils; these could also be obtained by Dimroth rearrangement of 2-(4-substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones under the same reaction conditions. 2-(4-Substituted phenylimino)-6-phenyl-5,6-dihydro-4H-1,3-thiazin-4-ones were synthesized from the corresponding thioureas under catalysis of boron trifluoride in chloroform.
Conformation of diastereoisomeric cyclo(neopentylglycyl-prolyls): NMR, X-ray, and CD studies
Authors: Bláha Karel , Buděšínský Miloš , Frič Ivo , Pospíšek Jan , Symerský Jindřich
Published: June 2010

Conformation of diastereoisomeric cyclo(L-neopentylglycyl-L-prolyl) (IV) and cyclo(D-neopentylglycyl-L-prolyl) (VIII) in solution was studied by 1H and 13C NMR spectroscopy. Both compounds have approximately the same conformation of the bicyclic moiety in which the 2,5-piperazinedione ring exists in the boat form with pseudoaxial proline H(α) atom, and the proline ring is in the C(γ)-exo conformation. Rotation of the neopentyl side chain is markedly hindered. In the trans-derivative VIII the side chain occupies a pseudoaxial position with staggered rotamer about the C(α)-C(β) bond, the tert-butyl group pointing from the ring in the direction of the nitrogen atom. The preferred rotamer of the cis-isomer markedly deviates from this staggered conformation in the exo-direction relative to the piperazine ring. X-Ray diffraction analysis shows that crystal conformation of the trans-isomer VIII is very similar to that in solution. According to CD measurements, steric interactions of the acyclic side chain with the dioxopiperazine ring lead to twisted boat conformations of this ring with non-planar amide groups. From comparison with other proline-containing cyclodipeptides it follows that the effect of these interactions depends on the side chain structure. The neopentyl side chain flattens the boat conformation and reduces the deviation of the amide groups from planarity.
Papain-catalyzed synthesis of 2-naphthylamides of N-acylamino acids and dipeptides
Authors: Čeřovský Václav , Saks Taťána , Jošt Karel
Published: June 2010

2-Naphthylamides of several N-acylamino acids were prepared by papain-catalyzed condensation reaction in acidic medium. Under the same conditions, papain catalyzed the synthesis of peptide bond between benzyloxycarbonylglycine and phenylalanine 2-naphthylamide and between benzyloxycarbonylserine and tyrosine 2-naphthylamide. Phenylalanine 2-naphthylamide was also acylated with benzyloxycarbonyl glycine methyl ester in an alkaline medium. For comparison, papain-catalyzed condensations of benzyloxycarbonyl-S-benzylcysteine or benzyloxycarbonylalanine with aniline and its derivatives, benzylamine, phenylhydrazine, cyclohexylamine and 1-naphthylamine, were studied.
Belousov–Zhabotinskii type oscillation reaction with glycerol and kinetics of reactions between the system components
Authors: Adamčíková Ľubica , Ševčík Peter
Published: June 2010

Glycerol causes chemical oscillations in Belousov-Zhabotinskii reaction in a closed system as well as in a reaction solution bubbled with nitrogen. Since the oxidation of glycerol with bromate ions does not proceed autocatalytically and bromine in the oxidation state 0 or +1 in the absence of light does not react with glycerol, hydrolysis of bromine is the probable source of bromide ions in the studied oscillation system.
Outer-sphere interaction of (S)-asparagine and (S)-glutamine with [Co(NH3)6]3+ ion and its possible role in ligand substitution
Authors: Jursík František
Published: June 2010

Optical activity of the achiral cation [Co(NH3)6]3+ is induced both by (S)-AsnONa and (S)-GlnONa, as shown by a negative Cotton effect in the 1A1g → 1T1g transition region. An outer-sphere interaction by three-point attachment of the amides can explain the fact that substitution reaction of [Co(NH3)6]3+ with the mentioned amides in an alkaline medium is unusually slow as compared with other amino acids.