bluuebunny/crossref_metadata_2025 huggingface dataset:
Nitration of some polyalkyl-3,5-dicyano-1,4-dihydropyridines and fragmentation of their products by electron impact
Authors: Kurfürst Antonín , Raclová Františka , Kuthan Josef
Published: January 2014

Dihydropyridines I-IV on treatment with nitric acid in acetic acid or acetic anhydride undergo nitration at the 2- or 6-methyl groups. Mass spectra of the products V-XI are interpreted and mechanism of the studied transformations is discussed.
Ionic dimerisation of trifluoropropenenitrile and its addition reactions with methyl trifluoropropenoate
Authors: Svoboda Jiří , Paleta Oldřich , Dědek Václav
Published: January 2014

Dimerisation of trifluoropropenenitrile (I) in the presence of potassium fluoride and tertiary amines afforded a mixture of stereoisomeric perfluoro-4-methyl-pentenedinitriles (II), higher-boiling compounds, and 2,3,3,3-tetrafluoropropanenitrile (III) which arises by proton transfer from the solvent molecule. Under optimum conditions, product II was obtained in about 50% yield. Reaction of the nitrile I with methyl trifluoropropenoate (IV) gave, besides the dimers II and V, the product of addition of the nitrile I to the propenoate, IV, i.e. methyl 4-cyanoperfluoro-2-pentenoate (VI), and the addition product of the propenoate IV to the nitrile I, i.e. methyl 4-cyanoperfluoro-2-methyl-3-butenoate (VII). The relative reactivity if I and IV is discussed. The ratio of stereoisomers in II, V, VI and VII indicates that the magnitude of the steric substituent effect, operating in the reaction mechanism, decreases in the order -CFCF3.(COOCH3) > -CFCF3(CN) > -COOCH3 > -CN.
Ionic dimerisation of methyl trifluoropropenoate
Authors: Paleta Oldřich , Havlů Václav , Dědek Václav
Published: January 2014

Dimerisation of methyl trifluoropropenoate (I) in solvents in the presence of potassium fluoride affords stereoisomeric dimethyl perfluoro-(4-methyl-2-pentene)dioates (III), the ratio of which depends on the reaction conditions. The reaction is accompanied by formation of methyl 2,3,3,3-tetrafluoropropenoate (IV), arising by proton transfer from the solvent to the carbanionic intermediate. Under suitable conditions complete conversion of the propenoate can be achieved and the dimer is obtained in 80-90% yield. Principal steps of the dimerisation were proved and the formation of configurational isomers is discussed in terms of kinetically controlled reaction.
Synthesis and polarographic investigation of 5-phenoxy-2-furaldehydes
Authors: Knoppová Viera , Beňo Anton , Kada Rudolf , Kováč Jaroslav
Published: January 2014

5-(4- Or 3-X-phenoxy)-2-furaldehydes were prepared from 5-bromo-2-furaldehyde and the respective sodium 4- or 3-X-phenolates (X = 4-Cl, 4-Br, 4-NO2, 4-CH3, 3-NO2, 4-CH3O, 4-COOC2H5, 4-SCH3, 3-NHCOCH3 in dimethyl sulfoxide. The transmission effect of a substituent on the reaction centre through oxygen is discussed on the basis of polarographic study of the CHO group.
The role of secondary alcoholic groups of D-galacturonan in its degradation with exo-D-galacturonanase
Authors: Heinrichová Kveta , Kohn Rudolf
Published: January 2014

The effect of exo-D-galacturonanase from carrot on O-acetyl derivatives of pectic acid of variousacetylation degree was studied. Substitution of hydroxyl groups at C(2) and C(3) of D-galactopyranuronic acid units influences the initial rate of degradation, degree of degradation and its maximum rate, the differences being found also in the time of limit degradations of the individual O-acetyl derivatives. Value of the apparent Michaelis constant increases with increase of substitution and value of Vmax changes. O-Acetyl derivatives act as a competitive inhibitor of degradation of D-galacturonan. The extent of the inhibition effect depends on the degree of substitution. The only product of enzymic reaction is D-galactopyranuronic acid, what indicates that no degradation of the terminal substituted unit of O-acetyl derivative of pectic acid takes place. Substitution of hydroxyl groups influences the affinity of the enzyme towards the modified substrate. The results let us presume that hydroxyl groups at C(2) and C(3) of galacturonic unit of pectic acid are essential for formation of the enzyme-substrate complex.
N-Acylated phenylalanine p-nitroanilides: New substrates for chymotrypsin
Authors: Kasafírek Evžen , Bartík Michal
Published: January 2014

Chromogenic substrates of the following types were synthesized: X-Phenylalanine p-nitroanilides, where X = acetyl, hydroxyacetyl, methoxyethoxyacetyl, and 3-carboxy-2-propenoyl, (glycyl)n-phenylalanine p-nitroanilides and 3-carboxypropanoyl(glycyl)n-phenylalanine p-nitroanilides, where n = 1,2,3, (glycyl)n-tyrosine p-nitroanilides and 3-carboxypropanoyl(glycyl)n-tyrosine p-nitroanilides, where n = 0,1,2, and also acetylhistidyl-glycyl-glycyl-phenylalanine p-nitroanilide. The constants Km, kcat and C (i.e. kcat/Km) were estimated for enzymic splitting by chymotrypsin. The greatest kcat values were found for 3-carboxypropanoylglycyl-glycyl-tyrosine p-nitroanilide and 3-carboxypropanoyl-glycyl-glycyl-phenylalanine p-nitroanilide, 40.5 and 16.9, respectively. The smallest Km value, 1.1 x 10-4 (mM) was observed with acetylhistidylglycyl-glycyl-phenylalanine p-nitroanilide, which exhibited also the greatest C constant, 115 000 (M-1 s-1).
Synthesis of analogues of the thyreotropin releasing factor containing 2-oxoimidazolidine-1-carboxylic acid
Authors: Kasafírek Evžen , Felt Vladimír , Krejčí Ivan , Michalský Jiří
Published: January 2014

2-Oxoimidazolidine-1-carbonyl-histidyl-proline amide (I) and 2-oxoimidazolidine-1-carbonyl-histidyl-phenylalanine amide (II) were synthesized by conventional chemical methods. 4,4'-Dimethoxybenzhydryl and 3,3',4,4'-tetramethoxybenzhydryl groups were used for protection of primary amide functions. Both analogues, I and II, did not exhibit the increase in thyroxine (radioimmunoassay) when applied to male rats intraperitoneally.
Decomposition kinetics of cobalt complexes of phenoxy radicals studied by EPR method
Authors: Omelka Ladislav , Tkáč Alexander
Published: January 2014

In bimolecular homolytic substitution reactions type SH2 between coordinated peroxy radicals [Co(III)]RO2 and partially hindered bisphenol 4,4'-thiobis-(3-methyl-6-tert-butylphenol) (an antioxidant with commercial name Santonox R) in non-polar medium at room temperature an equilibrium is established between free and Co(III)-coordinated phenoxy radicals. Increasing temperature shifts the equilibrium in favour of the decomplexed free radicals. The complexation-decomplexation process of phenoxy radicals is practically reversible up to 90°C. Polar coordinating solvents (methanol, H2O, diethyl ether, tetrahydrofurane) displace irreversibly the radicals from the complexes. From their decomposition kinetics at various temperatures activation energy of decomplexation by methanol has been determined (110 ± 8 kJ mol-1). The displaced free partially hindered phenoxy radicals are not sufficiently stable and undergo subsequent radical transformations (dimerization, intramolecular and intermolecular H-transfer) with effective activation energy about 67 kJ mol-1.
13C nuclear magnetic resonance study of cyclodipeptides containing 13C enriched hydrophobic amino acids
Authors: Vičar Jaroslav , Piriou François , Fromageot Pierre , Bláha Karel , Fermandjian Serge
Published: January 2014

The diastereoisomeric pairs of cyclodipeptides cis- and trans-cyclo(Ala-Ala), cyclo(Ala-Phe), cyclo(Val-Val) and cyclo(Leu-Leu) containing 85% 13C enriched amino-acid residues were synthesized and their 13C-13C coupling constants were measured. The combination of 13C-13C and 1H-1H coupling constants enabled to estimate unequivocally the side chain conformation of the valine and leucine residues.
Synthesis of 3-chloro-5-(4-methylpiperazino)-6,7-dihydro-5H-dibenzo[b,g]thiocin, an eight-membered ring homologue of the neuroleptic agent octoclothepin
Authors: Šindelář Karel , Holubek Jiří , Svátek Emil , Protiva Miroslav
Published: January 2014

Alkylation of diethyl malonate with 2-(4-chlorophenylthio)benzyl chloride, the following hydrolysis and decarboxylation gave 3-[2-(4-chlorophenylthio)phenyl]propionic acid (IV); its chloride was cyclized in low yield by treatment with aluminium chloride to 4-(4-chlorophenylthio)indanone (V). The corresponding methylpiperazine derivative VIII was prepared viaintermediates VI and VII. A reaction of 3-(2-mercaptophenyl)propionic acid with 5-chloro-2-iodobenzoic acid and the following esterification resulted in the diester XVI which was cyclized by a Dieckmann reaction using sodium hydride in toluene to give ethyl 3-chloro-5-hydroxy-7H-dibenzo[b,g]thiocin-6-carboxylate (XVII). The acid hydrolysis afforded the ketone XVIII which was transformed via the intermediates XX and XXI to the title compound II. The product has a mild central depressant activity but it lacks the character of a neuroleptic agent.
Neuroleptics of the 8-methylthio-10-piperazino-10,11-dihydrodibenzo[b,f]thiepin series: New compounds and new procedures
Authors: Jílek Jiří , Pomykáček Josef , Dlabač Antonín , Bartošová Marie , Protiva Miroslav
Published: January 2014

Heating of 8-methylthiodibenzo[b,f]thiepin-10(11H)-one with mono-p-toluenesulfonates of 1-methylpiperazine and piperazine in vacuo led in good yields to the enamines IX-XI, the first of which was reduced with zinc and acetic acid to the base I (methiothepin). The ester III(oxyprothepindecanoate) was obtained by reaction of the amino alcohol II (oxyprothepin) with decanoic acid in the presence of N,N'-carbonyldiimidazole and by substitution of 10-chloro-8-methylthio-10,11-dihydrobenzo[b,f]thiepin with 1-(3-decanoyloxypropyl)piperazine. The substitution reaction of the same chloro compound with piperazine gave two stereoisomeric 1,4-disubstituted piperazines V. Reaction of the amino alcohol II with octyl isocyanate afforded the carbamate VI, an isoster of oxyprothepin decanoate (III). This substance showed in the test of antiapomorphine activity in dogs the properties of a long-acting antiemetic. Two new potential metabolites (XII, XIII) of compounds I-III were synthesized and new pharmacological data are given for two further potential metabolites (XIV, XV) of oxyprothepin (II).
10-[4-(3-Hydroxypropyl)piperazino]-8-methylsulfonyl-10,11-dihydrodibenzo[b,f]thiepin and some related potential metabolites of the neuroleptic agents oxyprothepin and methiothepin
Authors: Valenta Vladimír , Dlabač Antonín , Bartošová Marie , Svátek Emil , Protiva Miroslav
Published: January 2014

Substitution reaction of 10-chloro-8-methylsulfonyl-10,11-dihydrodibenzo[b,f]thiepin with 1-(3-hydroxypropyl)piperazine afforded the title compound IV which was transformed by selective oxidation reactions to the sulfoxide X, N-oxide XII and N,S-dioxide XIII. The secondary amine VII was prepared via the carbamate VI and oxidized to the sulfoxide XI. Reaction of 10-chloro-8-methylsulfonyl-10,11-dihydrodibenzo[b,f]thiepin with ethylenediamine gave the diamine XIV which was oxidized to the corresponding sulfoxide XV. Compounds IV, VII and X-XV are potential metabolites of the neuroleptic agent oxyprothepin (II); compounds VII, XI, XIV and XV are potential metabolites of methiothepin (I). Out of the compounds prepared, only the title compound IV preserves the neuroleptic character.
On the synthesis of 4- and 5-pyrimidinyl-diphenyl-(1-imidazolyl)methanes and their antifungal activity
Authors: Buděšínský Zdeněk , Vavřina Josef , Langšádl Leon , Holubek Jiří
Published: January 2014

On reaction of phenylmagnesium bromide with ethyl ester of 5-chloro-2-methyl-, 5-chloro-2-methylthio-, 5-bromo-2-methylthio-4-pyrimidinecarboxylic acid and 2,4-dimethyl-5-pyrimidinecarboxylic acid (IIa, IIb, IIc, V) corresponding 4-pyrimidinyl- or 5-pyrimidinyl-diphenylmethanols (IIIa, IIIb, IIIc, VI) were obtained. On reaction of thionyl-bis-imidazole with these methanols (4- or 5-pyrimidinyl)-diphenyl-(1-imidazolyl)-methanes IVa, IVb, IVc and VII were prepared. Phenylmagnesium bromide reacted with ethyl 4-methyl-2-methylthio-5-pyrimidinecarboxylate (VIII) under formation of dihydro derivative IX. We were unable to prepare Grignard's reagent from 5-bromo-2-methylthiopyrimidine and magnesium; it reacted with ethylmagnesium bromide under formation of dihydro derivative I. 5-Chloro-2-methylthio-4-pyrimidinecarboxylic acid when heated with NaOH in dimethyl sulfoxide gave 5-hydroxy-2-methylsulfinyl-4-pyrimidinecarboxylic acid. Compounds IVb and IVc prevented the growth of Candida albicans in vitro at almost the same concentrations as clotrimazole.
Participation of 19-substituents in electrophilic additions to 6,7-unsaturated 5α-cholestane and B-homo 5α-cholestane derivatives; A case of competition between the participation of an ambident neighboring group and external nucleophile attack
Authors: Kočovský Pavel , Kohout Ladislav , Černý Václav
Published: January 2014

Hypobromous acid action upon the 6,7-unsaturated 19-substituted 5α-cholestans Va-Vc results in the formation of two types of products, the cyclic ethers IX as products of 5(O)n participation of the 19-substituent, and the bromohydrins X. All these compounds are formed from the 6α,7α-bromonium ions Va'-Vc'. Under the same conditions the B-homo-5α-cholestane derivatives VIIa-VIIc afforded solely the cyclic ethers XIV as products of 5(O)n participation of the 19-substituent in the cleavage of the bromonium ions VIIa'-VIIc'. Acid cleavage of the 6α,7α-epoxides VIb and VIc with aqueous perchloric acid or hydrobromic acid gave two types of products, i.e. the cyclic ethers XI and the diols XII or bromohydrines XIII. The cyclic ethers XI arise by 5(O)n participation of the 19-substituent. The B-homo-6α, 7α-epoxide VIIIc on cleavage with aqueous perchloric acid have solely the cyclic ether XVc and by treatment with hydrobromic acid VIIIc afforded the mixture of XVc, as the main product, and of the bromohydrin XVIc. Discussed is the similarity of the bromonium ion cleavage with the fission of the corresponding epoxides, the mechanism of these reactions and the difference in the behaviour of the isomeric olefins Ia-c, IIIa-c, Va-c and VIIa-c and epoxides IIb,c, IVb,c, VIb,c and VIIIb,c. The competition between ambident neighbouring group participation and external nucleophile attack is discussed as well as the dependence of the products ratio on the nucleophilicity of the attacking species.
Solvolysis of 5,6β-cyclopropano-5β-cholestane-3β,19-diol 3-acetate 19-p-toluenesulphonate
Authors: Fajkoš Jan , Joska Jiří , Tureček František
Published: January 2014

Acetolysis of 5,6β-cyclopropano-5β-cholestane-3β,19-diol 3-acetate 19-ptoluenesulphonate afforded 5,6β-cyclopropano-5(10)a-homo-19-nor-5β-cholest-1(10)-ene-3β-ol 3-acetate and 7β,19-cyclo-B-homo-5α-cholestane-3β,5-diol 3,5-diacetate.The structures of these products were established by spectral and chemical means.
Reaction of nucleosides with thionyl chloride; Preparation of the deoxy derivatives of cytidine and adenosine
Authors: Hřebabecký Hubert , Brokeš Josef , Beránek Jiří
Published: January 2014

On reaction of thionyl chloride with cytidine and adenosine in refluxing acetonitrile, the 5' -chloro-2',3' -sulphinyl derivatives I and VII are formed in a quantitative yield. On heating in dimethyl-formamide, compound I affords 5' -chloro-5' -deoxycyclocytidine (II) which is hydrolyzed in alkali to the arabinosyl derivative III; reduction of III with tributyltin hydride gives the 5' -deoxyarabinosyl derivative IV. The sulphinyl derivative I is hydrolyzed to 5' -chloro-5' -deoxycytidine (V) which is reduced to 5' -deoxycytidine (VI). Analogously, the sulphinyl derivative VII affords 5' -chloro-5' -deoxyadenosine (VIII) and the reduction of VIII gives 5' -deoxyadenosine (IX). Of these compounds, the 5' -chloro-5' -deoxyarabinosyl derivative as the only one shows an inhibitory effect towards the L1210 cell growth.
Synthesis of conjugates of 5'-O-carboxymethyl-5-halogeno-2'-deoxyuridines and 5'-O-carboxymethyl-5-halogenouridines with proteins
Authors: Pischel Helmut , Holý Antonín , Wagner Günther
Published: January 2014

5'-O-Carboxymethyl-2'-deoxyuridine (Ia), its 5-fluoro, 5-bromo and 5-iodo derivatives Ib-Id, and 5'-O-carboxymethyluridine (IIa) and its 5-halogeno derivatives IIb-IId, on reaction with isobutyl chloroformate and tri-n-butylamine afforded mixed anhydrides IIIa-IIId and IVa-IVd. Condensation of III and IV with human serum albumin or bovine gamma-globulin at pH 8.0 gave conjugates Va-Vd to VIIIa-VIIId, the yield of the covalently bound haptene being 28 to 43%.
Ribonuclease a catalyzed preparative synthesis of dinucleoside monophosphates containing uridine analogues
Authors: Kavunenko Antonina P. , Holý Antonín
Published: January 2014

Preparative synthesis of dinucleoside monophosphates, catalyzed by ribonuclease A, is described. Uridine 2',3' -cyclic phosphate was used as a donor, the acceptors being uridine (Ia), N3-methyl-uridine (Ib), 5-methyluridine (Ic), 6-methyluridine (Id), 3-(β-D-ribofuranosyl)uracil (IIa), 1-methyl-3-(β-D-ribofuranosyl)uracil (IIb), 6-azauridine (III) and 6-methyl-2'-deoxyuridine (IV). The obtained compounds of the type UpN (where N is the nucleoside moiety I-IV) were characterized by paper chromatography, electrophoresis and UV-spectra.
Investigation of recrystallization of collagen (I) employing contraction and statistical conformation properties
Authors: Galatík Antonín , Blažej Anton
Published: January 2014

The ability of collagen (I) to recrystallize by cooling after a thermal denaturation was attempted by a method of concentration energy and theoretical statistical conformation analysis. Contraction energy of the native collagen was 1.96 ± 0.6 J/g; that of denaturated collagen after cooling in contracted state 0.036 J/g and in the stretched state 0.45 ± 0.1 J/g. This corresponds to a 1.8 and 22.8% of recrystallization, respectively.

Theoretic calculation of the probable conformation of the whole sequence of α1(I) chain showed that approximately only 60% of sequences have the ability to form spontaneously stretched polypyrrolidine conformation, whereas approximately 34% of the chain was randomized. About 5% of amino acid sequences had a preferred α-helical conformation and terminal peptides, especially the C-tail have a high probability of extended conformation of a β-pleated sheat type. The collagen chain reveals a significant tendency to form reverse turn. Statistical conformation properties are compared with those of some model polypeptides.
Mechanism of inhibition of succinate oxidase by products of oxidation of o-dihydroxycoumarins
Authors: Zbořil Petr
Published: January 2014

Semiquinone is an intermediary product of the oxidation of daphnetin (7,8-dihydroxycoumarin) and esculetin (6,7-dihydroxycoumarin) by diphenol oxidase; its concentration rapidly decreases. When the oxidation is effected by ferricytochrome c, the concentration of the semiquinone remains practically constant for a long period. Similarly, the ability of the products of daphnetin oxidation by diphenol oxidase to inhibit succinate oxidase activity in mitochondrial fragments rapidly decreases with time; the decrease is considerably slower in the case of cytochrome c. The inhibitory activity of the product decreases with time also during esculetin oxidation by ferricyanide. This indicates that the inhibitory effects must be ascribed predominantly to the semiquinone, the quinone is less efficient. The inhibition of succinate oxidase or succinate dehydrogenase was strongly decreased when the enzyme preparation of Keilin and Hartree was incubated with esculetin and ferricyanide in the presence of KCN or under anaerobic conditions. This demonstrates that the reaction of the inhibitor with the enzyme either involves subsequent oxidations or that the inhibitor preferentially reacts with the oxidized form of the sensitive component of the respiratory chain. The second alternative is very little probable since there is no correlation between the degree of inhibition and the binding of the inhibitor to mitochondrial fragments.
Mode of effect of Ostruthin, a phenolic coumarin on respiration and oxidative phosphorylation of rat liver mitochondria
Authors: Dadák Vladimír , Zbořil Petr , Šanek Josef , Svoboda Augustin
Published: January 2014

Ostruthin (6-genaryl-7-hydroxycoumarin) in concentration of 5-30 nmol/mg protein behaves as an uncoupler. It eliminates the respiratory control in liver mitochondria, decreases the ratioof ADP/O uptake, and stimulates ATPase activity. It also acts as an inhibitor of the exchange reaction between 32Pi and ATP. Higher concentrations induce the swelling of mitochondria, bring about changes in the permeability of the membrane, and significantly alter the ultrastructure of mitochondria. A considerable quantity of mitochondrial proteins and a part of the phosphorus compounds are released into solution during this process. The investigation of the distribution of typical enzymes of membranes and matrix (monoamine oxidase, cytochrome oxidase, succinate dehydrogenase, and malate dehydrogenase) has shown that the mitochondrial components released come from matrix. Ostruthin concentrations higher than 50 nmol/mg protein cause fragmentation of membranes observable in ultrathin slices in the electron microscope. Fragmentation of both the inner and the outer mitochondrial membrane was demonstrated by the method of freeze etching.
Effect of temperature on catalytic hydrogen currents of native and modified bovine serum albumin
Authors: Kolthoff Izaak Maurits , Kihara S.
Published: January 2014

The effect of temperature has been studied on three different catalytic hydrogen currents observed voltammetrically and on two of them polarographically with serum albumin and modified products of albumin adsorbed on mercury. The so-called "active cobalt catalytic current", ic and "presodium current", ips increase with increasing temperature. The temperature effect on the so-called Brdi_ka currents. i1 and i2 was found to be quite different from that on ic or ips. In ammoniacal buffer (pH = 9.3) in the presence of cobalt(III) or (II) i1 has been found virtually the same at temperature between 4° and 40°C, whereas i2 greatly decreases with increasing temperature. Evidence has been presented that in the presence of Co(III) or Co(II) and at 4°C all disulfide groups in the protein used are reduced to sulfhydryl at potentials at which i1 and i2 are observed. It has been concluded that the ligands of the protein which complex with Co(III) or Co(II) or Co(0) are different at potentials at which i1 is observed than at which i2 is observed. In order to account for the abnormal temperature effect on i2 it has been proposed that the area of the section of protein which is the seat of i2 is being detached from the surface with increasing temperature and that this process is reversible.
Contribution to the application of scaled particle theory to prediction of the salting coefficient
Authors: Šír Zdeněk , Strnadová Ludmila , Rod Vladimír
Published: January 2014

The possibility of the extension of the scaled particle theory to nonelectrolytes moderately soluble in water and to aqueous electrolytes of various concentrations containing combinations of H+, K+, Na+, NH+4, Mg2+, OH-, Cl-, Br-, and SO2-4 ions was verified. Cyclohexanone, n-hexanol and benzene served as nonelectrolytes. The elaborated mathematical model was tested on the basis of experimental data published earlier.
Redox catalytic activity and stability of sulphonated polymers containing quinone groups
Authors: Blažek Václav , Prokop Zdeněk , Setínek Karel
Published: January 2014

In connection with the study of polymer redox catalysts, the properties of condensation products of hydroquinone with chloromethylated styrene-divinylbenzene copolymers have been examined in more detail. It was found that only part of the hydroquinone bonded is capable of electron exchange in aqueous medium and only this part is likely catalytically active for reaction in gaseous phase. The effect of reagents and temperature during preparation of polymers containing hydroquinone functional groups leads to destruction of macromolecules to form carbon clusters which have the same catalytic activity as functional hydroquinone groups. Only part of these clusters is, however, capable of electron exchange in aqueous medium. The higher the catalytic activity, the lower the thermal stability of the polymer.
The effect of composition of cobalt-molybdenum catalysts on their surface acidity and isomerisation activity
Authors: Vyskočil Vlastimil , Zdražil Miroslav
Published: January 2014

Kinetics of isomerisation of cyclohexene to methylcyclopentene proceeding as parallel reaction to hydrogenation of cyclohexene to cyclohexane on cobalt-molybdenum catalysts of different composition has been measured. The surface acidity of these catalysts was estimated from the difference in the adsorption of toluene and heptane which was measured by chromatographic method. In a series of catalysts containing molybdenum the acidity parallels isomerisation activity. Cobalt on alumina catalysts and alumina itself have greater acidity but exhibit lower isomerisation activity compared to the catalysts containing molybdenum.
Determination of microquantities of Fe, Mg, Ca, Cu, and Pb in lanthanoid minerals by atomic absorption spectrophotometry
Authors: Sopková Anna , Radváková Katarína
Published: January 2014

The decomposition of two lanthanoid minerals, viz fluorocarbonate bastnasite and phosphate monazite, is described. Iron present in the solution obtained is removed on anion exchanger. Atomic absorption spectrophotometry was applied to the determination of the minor elements present in the mineral, viz. copper, lead, calcium and magnesium. The measurement conditions for the determination of these elements in microquantities were established by using model solutions, and the accuracy and precision of determination were evaluated.
The use of coumarin derivatives in the preparation of fluorescence-labelled poly[N-(2-hydroxypropyl)methacrylamide]
Authors: Krejčoves Jiří , Drobník Jaroslav , Kálal Jaroslav
Published: January 2014

The possibilities of preparation of fluorescence-labelled poly[N-(2-hydroxypropyl)methacrylamide] by using 7-substituted 2H-1-benzopyran-2-ones (coumarins) in radical processes were investigated.
Study of reaction of thiourea with ethyl 3-oxobutanoate
Authors: Kaválek Jaromír , El-Bahaie Said , Macháček Vladimír , Štěrba Vojeslav
Published: January 2014

Base-catalyzed formation of 6-methyl-2-thiouracil (III) by reaction of thiourea (I) with ethyl 3-oxobutanoate (II) involves N-(3-oxobutanoyl)thiourea (XI) as the reaction intermediate. In acid medium the compounds I and II do not react. In contrast to literature data, base-catalyzed cyclization of ethyl 3-thioureido-2-butenoate (IV) does not produce the compound III, but produces 2-amino-4-methyl-6-oxo-1,3-thiazine.
Transformation of chlorofluoroethyldiethylamines to N,N-diethyldifluoroacetamide
Authors: Liška František , Hampl František , Dědek Václav
Published: January 2014

Hydrolysis of 2-chloro-1,1,2-trifluoroethyldiethylamine (I) and 2,2-dichloro-1,1-difluoroethyl-diethylamine (II) in the presence of triethylamine afforded N,N-diethylchlorofluoroacetamide (VII) and N.N-diethyldichloroacetamide (VIII), respectively. Triethylamine hydrofluoride, arising in the reaction, was used for fluorination and transformation of the amides VII and VIII to N,N-diethyldifluoroacetamide (VI). The C-Cl bond of the CHClF group in VII proved to be more reactive in nucleophilic substitution with fluoride ion than the corresponding bond in the CHCl2 group of VIII.
Some condensation products of ergoline - I Derivatives with ketones
Authors: Křepelka Jiří , Holubek Jiří , Semonský Miroslav
Published: January 2014

Monotopic bis-ergolin-2-yl derivatives of alkanes and cycloalkanes (I-VIII) were prepared on reaction of derivatives of ergoline-I (XI-XIV) with ketones in the presence of sulfuric acid or p-toluenesulfonic acid. Esterification of compound XV with cyclohexanol under catalysis with-p-toluenesulfonic acid gave condensation product IX after previous separation of cyclohexyl ester XVI. The condensation products did not exhibit prolactin inhibiting effect.
Naphthacenequinone derivatives from a mutant strain of Streptomyces coeruleorubidus
Authors: Jizba Josef V. , Sedmera Petr , Vokoun Jindřich , Blumauerová Margita , Vaněk Zdenko
Published: January 2014

Five metabolites were isolated from a mutant strain of Streptomyces coeruleorubidus. Structures IX-XIII were proposed on the basis of their 1H and 13C-NMR, IR, UV/VIS and mass spectra.
Activation of vasopressin hormonogens by kidney aminoacylarylamidase; Study in vitro
Authors: Hauzer Karel , Barth Tomislav , Jošt Karel
Published: January 2014

Under conditions in vitro the mammalian kidney aminoacylarylamidase splits off the individual glycine residues from the hormonogens of vasopressin and its analogs of the triglycyl-vasopressin type (triglycyl[8-lysine]vasopressin, triglycyl[8-ornithine]vasopressin and des-glycineamide triglycyl[8-lysine]vasopressin) generating consequently the hormone or its analogues. The time course of the reaction was followed by the biological method (pressoric assy) and by determing the concentration of the liberated glycine. The generated hormone or its analogues are resistant to the action of the enzyme used.
Study of nickel-molybdenum catalysts for methanation of carbon monoxide
Authors: Taras Petr , Pospíšil Milan
Published: January 2014

Catalytic activity of nickel-molybdenum catalysts for methanation of carbon monoxide and hydrogen was studied by means of differential scanning calorimetry. The activity of NiMoOx systems exceeds that of carrier-free nickel if x < 2, and is conditioned by the oxidation degree of molybdenum, changing in dependence on the composition in the region Mo-MoO2. The activity of the catalysts is adversely affected by irradiation by fast neutrons, dose 28.1 Gy, or by γ rays using doses in the region 0.8-52 kGy. The system is most susceptible to irradiation in the region of low concentrations of the minor component (about 1 mol.%). The dependence of changes in catalytic activity of γ-irradiated samples on the dose exhibits a maximum in the range of 2-5 kGy. The changes in catalytic activity are stimulated by the change of reactivity of the starting mixed oxides, leading to different kinetics of their reduction and modification of their adsorption properties. The irradiation of the catalysts results in lowered concentration of the active centres for the methanation reaction.
The electronic spectra of nickel(II) bis(dithiocarbamate) chelates
Authors: Oktavec Drahomír , Síleš Bohumil , Štefanec Jozef , Korgová Elena , Garaj Ján
Published: January 2014

The synthesis and electronic spectra of the chelates of nickel(II) dithiocarbamates with ligands derived from dimethyl-, diethyl-, dipropyl-, dibutyl-, dipentyl-, dihexyl-, diheptyl-, dioctyl-, diisopropyl-, methylisopropylamine, piperidine, morpholine and piperazine are discussed. The absorption bands in the chelate spectra around 220 and 245 nm are assigned to absorption localized primarily in the S-C=S and N-C=S ligand groups. The analytically most important band with λmax around 330 nm assigned to M-L charge transfer is affected by alkyl substituents on the nitrogen atom and by the solvent polarity. The lengthening of the alkyl chain causes the increase in the intensity of the band and red-shift of its λmax; the increase of the polarity of the solvent leads to an increase in the band intensity and a blue shift.
Study of reaction of 5-hydroxy-6-(2-hydroxy-5-sulfophenylazo)benzo(a)-phenazine with vanadates in the presence of Septonex
Authors: Son Nguyen Truong , Kotouček Milan , Ružička Eduard
Published: January 2014

Reaction of 5-hydroxy-6-(2-hydroxy-5-sulfophenylazo)benzo(a)phenazine with vanadates in aqueous medium was studied in the presence and in the absence of the tenside Septonex. In acidic medium (pH 2-6), the complex VO2L is formed in both cases. The equilibrium constants for the equilibria studied were calculated and a procedure was suggested for spectrophotometric determination of vanadium.
Model of drying mechanism of the chloroprene latex foil and its relation to experimental results
Authors: Langfelder Ivan , Beňa Ján
Published: January 2014

Theoretical model of convective drying is proposed for the chloroprene latex foil, which is the intermediate product in the production of chloroprene rubber. The model is based on the assumption that drying of this material takes place as evaporation from the free bed surface as steadily decreasing evaporation surface. This assumption is in agreement with the fact that drying at the beginning of the process takes place in the period of decreasing velocity but, nevertheless, it is effected by external hydrodynamic conditions. Theoretical and experimental results are compared and the suitability of the model is discussed. It is possible to expect that drying of latex foils, coats and films of another origin has a similar mechanism and that the obtained results have a large variety of application.
Preparation of higher adamantane homologues by reaction of adamantan-1-ol with heptenes in sulfuric acid
Authors: Vodička Luděk , Burkhard Jiří , Janků Josef
Published: January 2014

Reaction of adamantan-1-ol with heptenes in conc. sulfuric acid affords a complicated mixture of hydrocarbons, containing heptyladamantanes, diheptyladamantanes, tetradecyladamantanes, diadamantylheptanes and adamantyl-heptyladamantylheptanes. The reaction mixture can be separated into narrower fractions containing hydrocarbons of approximately equal molecular weight. The method can be utilized for the preparation of technical mixtures of high-boiling alkyladamantanes.
Substituent effects in electronic spectroscopy: Correlations with Platt spectroscopic moments
Authors: Exner Otto
Published: January 2014

Two correlation equations for the intensity of the 1Lb band in benzene derivatives were tested: the classic theory of Platt, Eq. (1), and the linear modification suggested by Ballester, Eq. (2). A systematic and statistically correct comparison of mono- and disubstituted derivatives revealed that Eq. (1) holds for substituents which are not conjugated or only slightly conjugated with the benzene ring, both in the ground and in the excited state (alkyls, Cl, Br, I, CH2X, CHal3). Some symmetrical properties of the substituents might be also of importance but their spectral properties (the spectroscopic moment itself, or the spectral shift) are not decisive. The conjugated substituents deviate from Eq. (1) in such a sense that the cumulative substituent effect is less than predicted; a part of the deviation may be approximately described by Eq. (2) but an exact range of validity cannot be determined. The spectroscopic moments depend mainly on the mesomeric effect of the substituent and quite little on its inductive effect; they cannot, however, be expressed only by a combination of these two effects as determined from the ground state properties. This was demonstrated on the series of compounds C6H5CH2X since the correlation with σI constants revealed only a general trend.
The electronic effect of silyl groups in different XYZSi-R systems
Authors: Pola Josef , Chvalovský Václav
Published: January 2014

The electronic effect parameter σ for XYZSi-R compounds as silyl hydrides XYZSiH, alkoxysilanes XYZSiOL (L = alkyl or substituted alkyl) and α-carbofunctional silanes XYZSiCH2Y (Y = Cl and OL) having X, Y and Z substituents of various electron-donating and electronaccepting ability has been established by a linear regression analysis of the IR and NQR data on these compounds. It is shown that no universal scale of the σ constant for silyl XYZSi-groups can be established. The electronic effect transmission of the X, Y and Z substituents through the silicon depends on the type of the intramolecular interaction between the silicon and the R group and the electronic effect parameter of silyl groups should be treated as a variable whose exact value depends on the nature of the particular molecule.
Influence of nitrogen ligands on synergic effect of metal catalysts in oxidation of alkylaromatic compounds
Authors: Hronec Milan , Holotík Štefan , Ilavský Ján
Published: January 2014

Synergic effect of metal mixtures Co-Mn, Co-Ce and Co-U in oxidation of 1,2,4- and 1,3,5-trimethylbenzenes dissolved in acetic acid has been studied in dependence of the presence of nitrogen ligands 2,2',2''-nitrilotrisethanol, 1,6-hexanediamine and pyridine. The complex CoBr2Py2 and its equimolar mixture with the complex MnBr2Py2 are highly active in oxidation of alkyl-aromatic derivatives containing other alkyl than methyl. Their activity has been tested experimentally in oxidations of ethylbenzene, 1,3- and 1,2-dimethylbenzenes, 1-ethyl-4-methylbenzene, (1-methylethyl)benzene, propylbenzene, 1-methyl-4-(1-methylethyl)benzene, dodecylbenzene, 1,3-diethylbenzene and 4-octyl-1,1'-biphenyl.
Stereoselective photochemical addition of acetaldehyde to the products of Clauson-Kaas reaction
Authors: Šrogl Jan , Janda Miroslav , Liška František , Stibor Ivan
Published: January 2014

Photochemical addition of acetaldehyde to 2,5-dimethoxy-2,5-dihydrofuran (I) (and the pure stereoisomers Ia and Ib), methyl 2,5-dimethoxy-2,5-dihydrofuran-2-carboxylate (II), methyl 2,5-dimethoxy-2,5-dihydrofuran-3-carboxylate (III) and cis-2-hydroxymethyl-2,5-dimethoxy-2,5-dihydrofuran (IV) was studied. The acetyl group enters into the position 4 of the arising tetrahydrofuran system, trans relative to the ester or hydroxymethyl group in the position 2.
Esters of 1-p-chlorobenzoyl-5-methoxy-2-methyl-3-indolylacetic acid
Authors: Fišnerová Ludmila , Rábek Vlastimil , Němeček Oldřich
Published: January 2014

Reactions of imidazolide of 1-p-chlorobenzoyl-5-methoxy-2-methyl-3-indolylacetic acid, prepared from the acid and N,N'-carbonyldiimidazole, with the optically active forms of 2-phenyl-3-hydroxypropane acid and with the inactive forms of p-chloro-, p-isopropyl-, and p-isobutyl-2-phenyl-3-hydroxypropane acids gave the corresponding esters. The compounds were tested for antiinflammatory activity.
Synthesis of 14-deoxy-14α-strophanthidol
Authors: Kočovský Pavel , Černý Václav
Published: January 2014

A thirteen-step synthesis of 3β,5,19-trihydroxy-5β, 14α-card-20(22)-enolide (I, title compound) from 3β-acetoxy-5-pregnen-20-one (V) is described. A characteristic feature of this approach is the introduction of the 5β-hydroxyl group by hypobromous acid addition to the 5,6-unsaturated-19-acetoxy derivative XV which proceeds with 6(O)π n participation of the acetoxy group (XV(r)XVI(r)XVII).
Synthesis of some nucleolipids
Authors: Smrt Jiří , Hynie Sixtus
Published: January 2014

Adenosine 5'-phosphate P-(2-oleamidoethyl) ester (I), P-(2-palmitamidoethyl) ester (II), P-(1-hexadecyl ester (III), P-(1-octadecyl) ester (IV) and P-(1-adamantyl) ester (V) were prepared by the reaction of N, O2', O3'-triacetyladenosine 5'-phosphate with appropriate hydroxy derivative in the presence of N,N'-dicyclohexylcarbodiimide followed by the action of ammonia. 2', 3'-O-Ethoxymethyleneadenosine 5'-phosphate P-(2-palmitamidoethyl) ester (IX) was prepared by the reaction of 2-chloro-4,5-dimethyl-2-oxo-1,3,2-dioxaphosphole (VI) with N-(2-hydroxyethyl)palmitamide (VII) and 2',3'-O-ethoxymethyleneadenosine (VIII) followed by the action of aqueous triethylamine. Adenosine 5'-phospho-(1-decyl)amidate (X) and adenosine 5'-phospho-(1-pentadecyl)amidate (XI) were prepared by the action of 1-decylamine and 1-pentadecylamine resp. on adenosine 5'-phosphate in the presence of N,N'-dicyclohexylcarbodiimide. The compounds I-VIII are not degraded by shake venom diesterase. The inhibition of the activity of adenylate cyclase is dependent on the length of the aliphatic chain involved.
Conformation of branched polypeptides based on poly(L-lysine): Circular dichroism study
Authors: Votavová Hana , Hudecz Ferenc , Kajtár Judit , Szekerke Mária , Šponar Jaroslav , Bláha Karel
Published: January 2014

Circular dichroism (CD) spectra of branched (multichain) polypeptides based on poly(L-lysine) with DL-alanine and other amino-acid residues in the side chain have been measured under various conditions of pH. The spectra were interpreted using spectra of poly(L-lysine) as standard. No straightforward correlation between polypeptide CD spectra and their structure could be detected. The contribution of the side chain CD to that of the main chain is additive in some cases, but in other cases qualitatively different CD spectra arise. The reason for this CD behavior is discussed.
Conversion of monosaccharides into their corresponding 2-glycosuloses by intact cells of the basidiomycete Oudemansiella mucida
Authors: Volc Jindřich , Sedmera Petr , Musílek Vladimír
Published: January 2014

The production of D-arabino, D-lyxo, and D-ribo-2-hexosuloses and D-threo-2-pentosuloses from their respective aldoses was demonstrated with washed mycelium suspensions of the basidiomycete Oudemansiella mucida. L-Sorbose was shown to be converted into D-threo-2,5-hexodiulose. The dicarbonyl sugar produced were isolated as their hydrazones, whose structures were inferred from spectroscopic evidence and the method of preparation.
Pseudobase formation in 2-methylpapaverinium cations and their biotransformation by enzymes of rat liver homogenates in vitro
Authors: Walterová Daniela , Preininger Vladimír , Dolejš Ladislav , Grambal František , Kyselý Miroslav , Válka Ivo , Šimánek Vilím
Published: January 2014

2-Methylpapaverinium iodide (I), 2'-hydroxymethyl-2-methylpapaverinium iodide (IX), and 2-methyl-3,4-dihydropapaverinium iodide (X. CH3I) form pseudobase by addition of hydroxide ions to the C(1)=N(+) bond. 2'-Hydroxymethyl-2-methyl-3,4-dihydropapaverinium iodide (XV) and 2'-hydroxymethyl-2-methyl-9-oxo-3,4-dihydropapaverinium iodide (XVI) react with hydroxide ions in aqueous medium under formation of cyclic pseudobases XVII and XVIII. The equilibrium constants (KR+) of pseudobase formation have been measured in aqueous ethanol (1 : 1 w/w, 25°C, ionic strength 0.1). The quaternary papaverinium derivatives are metabolized to isoquinilones and carbonyl compounds by means of rat liver enzymes. The role of pseudobases in these biotransformations has been discussed and biogenetic conclusions have been drawn.
Equation of state of a Lennard-Jones 12-6 pairwise additive fluid
Authors: Sýs Jan , Malijevský Anatol
Published: January 2014

An empirical equation of state was proposed, which is based on pseudoexperimental data on the state behaviour. The equation can be used at reduced temperatures from the range 0.7-100.0 and reduced densities up to 2. Calculated compressibility factors and critical properties agree well with available literature data.
Studies on rotational barriers in alkyl halogenides by means of vibrational spectroscopy
Authors: Bureš Michal , Černý Čestmír
Published: January 2014

A simple model describing the influence of the neighbouring molecules on the mechanism of the internal rotation in a given molecule has been proposed which allows the calculation of the barrier hindering the internal rotation in the ideal gaseous state from the temperature dependencyof the infrared spectra. To ascertain its adequacy, the kinetics of conformational transitions in seven halogenated alkanes has been investigated, and values of the activation enthalpies accompanying the internal rotation in a solution as well as the rotational barriers in the ideal gaseous state have been determined.
Calculation of the dynamics of concentration profile in a reactor simulated by a stagewise model
Authors: Košuth Jaroslav , Ilavský Ján
Published: January 2014

Dynamics has been examined of the concentration profile in a reactor simulated by the stagewise model under the isothermal conditions. Appropriate set of nonlinear differential equations has been solved iteratively using the Newton-Raphson method. Computed results have been compared with experimental data.
Mechanism of the propagation step in the anionic polymerization of styrene
Authors: Kašpar Miroslav , Trekoval Jiří
Published: January 2014

The paper is dealing with an investigation of the kinetic dependence of the propagation step in the anionic coordination polymerization of styrene in benzene at 303 K with "living" oligostyryllithium as initiator at the onset of the reaction. A short but distinct induction period was found, indicating a preceding slow reaction leading to the formation of a reactive intermediate, which behaves as the initiator of the reaction. Using results obtained in the first paper of this series, a new mechanism of propagation has been suggested, the mathematical solution of which is correlated with experimental data.
Quantum-chemical study of substituent effects in meta and para substituted phenyl isothiocyanates in π-electronic approximation
Authors: Danihel Ivan , Kristian Pavol , Kuthan Josef , Minčíková Mária
Published: January 2014

HMO and PPP calculations of a series of meta and para substituted phenyl isothiocyanates have been carried out with the aim of study of the substituent effects on the reaction centre of these compounds. The transition state of nucleophilic addition reaction of phenyl isothiocyanates has been approximated by two models, and the calculated localization energies at the carbon atom of NCS group have been investigated with respect to logarithms of rate constants of the nucleophilic reaction and to σ constants. Whereas in the former relation (i.e. localization energies vs log k) rough trends only have been found, the latter one (i.e. localization energies or π-electron densities vs σ) shows statistically significant linear correlations.
Velocity of rearrangement of ortho-substituted 3-(X-benzal)phthalides into 2-(X-phenyl)-1,3-indanediones and study of ortho-effect
Authors: Krasnec Ľudovít , Hrnčiar Pavol , Gáplovský Anton
Published: January 2014

Velocity of the second order rearrangement of ortho-substituted 3-(X-benzal)phthalides into respective 2-(X-phenyl)-1,3-indanediones by action of methanolic sodium methoxide has been studied spectrophotometrically. The values of logarithm of the rate constant obtained by extrapolation of the concentration dependences to zero concentration of methoxide have been correlated with σ, σ0, σ+, F, R, and Es constants of the substituents and with the Charton ν constant for the ortho-substituted derivatives. The obtained dependences log k vs the mentioned constants have been compared with the corresponding dependences of the rearrangement of the meta- and para-substituted 3-(X-benzal)phthalides into the respective 3-(X-phenyl)-1,3-indanediones. Transmission of the substituent effect on the reaction centre is almost the same from ortho and from para position. Possible ortho-effect and steric hindrance of the substituents have been followed.
Synthesis of substituted 4-anilinoquinazolines
Authors: Stankovský Štefan , Martvoň Augustin
Published: January 2014

Synthesis of substituted 4-anilinoquinazolines by means of a reaction of amidinoyl isothiocyanates with aromatic isothiocyanates is described. The probable mechanism of the reaction is discussed and characteristic spectral data of the prepared substances are presented.