bluuebunny/crossref_metadata_2025 huggingface dataset:
Certain problems with the application of stochastic diffusion processes for description of chemical engineering phenomena; Diffusion equations in curvilinear coordinates
Authors: Kudrna Vladimír
Published: August 2009

Parabolic partial differential equations used in chemical engineering for the description of mass transport and heat transfer and analogous relationship derived in stochastic processes theory are given. A standard transformation procedure is applied, allowing these relations to be generally written in curvilinear coordinates and particular expressions for cylindrical and spherical coordinates to be derived. The relation between the probability density for the position of a discernible particle and the concentration of a set of such particles is discussed.
Palladium-catalyzed carbonylation of 1,5-cyclooctadiene. Effects of temperature and pressure
Authors: Anderson Curtis B. , Marković Rade
Published: August 2009

The influence of temperature and carbon monoxide pressure on the course of oxidative carbonylation reaction of 1,5-cyclooctadiene in the presence of the palladium(II) salts as a catalyst, was investigated.
Synthesis and application of some new furoquinolinediones as bactericides
Authors: Yanni Amal S. , Khalil Zarif H.
Published: August 2009

Furo[3,2-g]quinoline-4,9-diones were prepared through the reaction of active methylene compounds with 6,7-dichloroquinoline-5,8-dione, either by one step or two step method. Benzo[b]- and naphtol[1,2-b or 2,1-b]furo[3,2-g]quinolinediones were also prepared through the reaction of 6,7-dichloroquinoline-5,8-dione with phenols and naphtols in presence of pyridine. The structure of the synthesized compounds was determined by elemental and spectral analysis.
Beryllium and magnesium hydroxides and fluorides
Authors: Zahradník Rudolf , Brázda Ota , Hess B. Andes
Published: August 2009

A theoretical study of the reactivity of BeF2, Be(OH)2, BeF(OH), MgF2, Mg(OH)2 and MgF(OH) was carried out at the MPn (n = 2, 3, 4)/6-31G**//SCF/6-31G** and CCD/6-31G**//SCF//6-31G** levels. Geometries and harmonic frequencies of the normal vibrational modes of the studied molecules are tabulated. Reaction energies and heats of reaction of MF2 + OH- MF(OH) + F- and MF(OH) + OH- MF(OH)2 + F- (M = Be, Mg) have been calculated and estimates for analogous processes involving calcium have been provided.
A simple method for estimating vaporization properties of pheromone-like acetates from their molecular structures
Authors: Koutek Bohumír , Hoskovec Michal , Vrkoč Jan
Published: August 2009

A simple computational method has been developed to determine vapor pressures of pheromone-like acetates, This input parameters required, i.e. critical temperatures and critical pressures are obtained from the known molecular structures by using group contribution methods. Subsequently, the vapor pressures are estimated by the three parameter corresponding states equation of Lee and Kesler. The validity of this approach was tested on a homogeneous experimental material (eleven C10 to C16 acetates) by standard methods of statistical analysis, as well as by comparison of the results with corresponding experimental data. When compared with GC based experimental values, the estimated vapor pressures show mean relative error ±10%, achieving thus a better accuracy than other experimental methods when compared among themselves. A close correlation, viz. In t1/2 = -0.294 In P + 1.82 (r = 0.9986) has been found between first order half-lives for evaporative loss of acetates from rubber septa and calculated vapor pressures.
Spectrophotometric study of the effect of sodium dodecyl sulphate on the acid-base behaviour of 4-(2-pyridylazo)-resorcinol
Authors: Bílý Jiří , Čermáková Ludmila , Knapp Jiří
Published: August 2009

The values of the apparent dissociation constants of the azo dye 4-(2-pyridylazo)-resorcinol (PAR) have been found in the presence of sub- and supercritical concentrations of the anionogenic tenside sodium dodecyl sulphate (SDS) and the effects of the strong electrolytes NaCl and NaNO3 were also evaluated. In both electrolytes, the pKan values initially are independent of the SDS concentration and then increase. Spectrophotometric and surface tension measurements were employed to determine the critical micelle concentration (cmc) of SDS alone and in the presence of PAR and the given electrolytes. The determined cmc values were in the range 0.20–3.02 mmol l-1 and dependent on the type and concentration of the particular additive.
Structure of a copper(II) complex with a non-symmetrical tetradentate Schiff base
Authors: Kratochvíl Bohumil , Ondráček Jan , Novotný Jiří , Haber Václav
Published: August 2009

The structure of (1-phenyl-3-{2-[(2-aminoethyl)amino]ethylimino}-1-buten-1-olato-O,N, N’,N”)-copper(II) perchlorate, [Cu(baden)]ClO4 was solved by Patterson and Fourier techniques and refined anisotropically to R = 0.066 for 2 205 unique observed reflections. The title complex (C14H20ClCuN3O5) crystallizes in the P21/c space group with the lattice parameters a = 10.435(1), b = 20.745(2), c = 8.457(1) Å, β = 108.56(1)°, Z = 4. The complex cation including the baden ligand contains two five-membered and one six-membered chelate rings, and the phenyl ring. The perchlorate anion is disordered. Two perchlorate oxygen positions, O22A and O33B, each with one half occupation factor value and four N3O donor atoms from the baden ligand complete the coordination geometry about the Cu atom on the square pyramid [Cu-O22A = 2.655(11)Å and Cu-O33B = 2.855(10)Å]. Weak hydrogen bonds among cations and anions were found in the structure.
A study of effect of temperature on the influence of medium on the reaction of triethylamine with ethyl iodide
Authors: Bekárek Vojtěch , Nevěčná Taťjana
Published: August 2009

The rate constants of the reaction of triethylamine with ethyl iodide have been measured in 15 solvents at the temperatures of 293, 313, 333 and 373 K. The solvent characteristics by Kamlet and Taft and those by Pytela have been found to be excellently applicable to evaluation of influence of medium on this reaction at all the temperature mentioned. However, these methods give different results with regard to the proton-donor effects of solvents on the reaction.
Anhydrobetulin and its derivatives
Authors: Vystrčil Alois , Křeček Václav , Protiva Jiří , Buděšínský Miloš
Published: August 2009

The structure of anhydrobetulin II and its derivatives I, III and IV has been solved using 1H and 13C NMR spectra, mass spectra and chemical transformations. It has been proven that in addition reactions the trisubstituted double bond is attacked selectively from the α-side under formation of D/E cis-annelated derivatives VIII, X and XI. The 22-oxo derivative XIII exhibits an anomalous Cotton effect and, in contrast to its saturated analogue XXVII,it is not epimerized in alkaline medium. Trinordiketone XXI easily epimerizes to a mixture in which the 17βH-epimer XXIb predominates, trinorketone XXIV is stable only if the annelation of rings D and E is trans. These differences are explained in terms of steric interactions of substituents in position 19. The steric course of reduction of ketones XIII and XXIV with sodium borohydride is described.
CD of primary amines and 1- or 3-substituted tetrahydroisoquinolines in presence of [Rh2(O2CCH3)4]
Authors: Diener Wolfgang , Frelek Jadwiga , Snatzke Günter
Published: August 2009

The syntheses of (S)-(-)-1,2-dimethyl-1,2,3,4-tetrahydroisoquinoline (IX) and (S)-(+)-2,3-dimethyl-1,2,3,4-tetrahydroisoquinoline (XVI) [ via (S)-1-benzoyl-N-ethoxycarbonyl ethylamine (XI)] in optically pure form and with known absolute configuration is described. The CD and NMR spectra of these compounds and of most of their intermediates are given, and from these data could be deduced, that the N-methyl groups of the two bases IX and XVI adopt different conformations in solution, but the same (viz. axial) in their complexes with [Rh2(OAc)4].
Infrared spectra of 2α-substituted 3-oxotriterpenoids and conformation of ring A
Authors: Klinot Jiří , Hilgard Stanislav , Krijt Jakub , Olšovský Petr
Published: August 2009

Infrared spectra of triterpenoid 19β,28-epoxy-18α-oleanane 3-ketones I - VI in the region of carbonyl stretching frequencies have been studied. Comparison of the spectra of crystals with those of solutions in various solvents, together with comparison of fundamental C=O frequencies with their first overtone leads to the conclusion that the doublet character of the carbonyl band in the solution of ketones I - IV with polar substituent in position 2α is caused by the chair-boat equilibrium of the ring A.
The oxidation of progesterone under GoAggIII conditions
Authors: Barton Derek H. R. , Doller Dario
Published: August 2009

The oxidation of pregn-4-ene-3,20-dione (progesterone) by the GoAggIII system (aqueous hydrogen peroxide, ferric chloride, picolinic acid in pyridine-acetic acid solution) has been investigated. Two tri-keto derivatives were isolated and identified as pregn-4-ene-3,6,20-trione and pregn-4-ene-3,12,20-trione. The third major product isolated was identified as the unstable 5α-formyl-A-nor-pregnane-3,20-dione, which deformylated spontaneously to A-nor-5β-pregnane-3,20-dione. A mechanism for the A-ring contraction is proposed, based upon the participation of a carbon-Fe(V) intermediate.
Unusual reactions of guaiazulene with N-bromosuccinimide and synthesis of variously functionalized azulenes using these reactions
Authors: Nozoe Tetsuo , Shindo Kimio , Wakabayashi Hidetsugu , Kurihara Teruo , Ishikawa Sumio
Published: August 2009

Treatment of guaiazulene (Ia) with NBS in benzene gives various, side-chain-brominated compounds, but in hexane it affords exclusively 3-bromoguaiazulene (Id). Compound Id is stable in hexane at 5°C in the absence of oxygen, whereas in benzene it changes very rapidly to a mixture of similar compounds as those directly obtained from Ia and NBS in benzene. Possible pathways for the formation of these compounds are briefly discussed. By utilizing these reactions, various kinds of side-chain functionalized azulenes that are otherwise not available by conventional methods can be readily prepared from Ia.
Reactivity of triformylmethane. I. Reactions of triformylmethane with selected types of amino compounds
Authors: Arnold Zdeněk , Buděšínský Miloš , Pánková Magdalena
Published: August 2009

Reactions of triformylmethane with various types of amino compounds were investigated. Besides with ammonia, triformylmethane reacts spontaneously with primary amines, aminoacids and their esters, urea and related compounds including carbamic acid derivatives. Reactions with amides of carboxylic and sulfonic acids require catalysis with Lewis acids. Primary products are aminomethylenemalonaldehyde derivatives IIIa-IIIv. Reactions of triformylmethane with excess of selected primary amines and two secondary amines (dimethylamine and morpholine) were also studied.
Enantioselective addition of optically active organotitanium reagents to benzaldehyde
Authors: Červinka Otakar , Pátek Marcel , Stružka Vladimír
Published: August 2009

Addition of optically active alkyltitanium (IV) reagents IIb and IIc to benzaldehyde afforded optically active 1-phenylethanol (V) of 37-48% optical purity and 1-phenylpentanol (VI) of 10-24% optical purity. Reagents IIb and IIc were prepared with the use of (1R,2S)-(-)-1-phenyl-1,2-propanediol (III) and (1R,2S)-(+)-1-cyclohexyl-1,2-propanediol (IV) as optically active components. Relations between the enantioselectivity achieved and reaction conditions are discussed.
A convenient synthesis of homochiral δ-alkylated α,β-unsaturated δ-lactones
Authors: Høyer Thomas , Kjær Anders , Lykkesfeldt Jens
Published: August 2009

The tert-butyl propiolate ion serves as a convenient and efficient nucleophile in boron trifluoride-catalyzed openings of homochiral, mono-substituted epoxides. The resulting tert-butyl 5-hydroxy-2-alkynoates are converted into the title compounds upon semihydrogenation followed by acid hydrolysis. Specific examples include the synthesis of parasorbic acid and massoilactone, two naturally derived lactones of the present type. The scope of the synthetic protocol is discussed.
11,13-Methylenation of sesquiterpene exomethylene-γ-lactones: Synthesis of sesquiterpene cyclopropyl-γ-lactones
Authors: Appendino Giovanni , Ghilardi Elisabetta , Cravotto Giancarlo , Gariboldi Pierluigi
Published: August 2009

11,13-Methylene derivatives of sesquiterpene exomethylene-γ-lactones were prepared by reaction of diazomethane and photolysis of the resulting pyrazoline adduct(s). Variable amounts of exomethylene- and ethylidene-γ-lactones were also formed in the photolysis reaction. These compounds could bee removed after reaction with diethylamine and chromatography on a bilayer (basic alumina/silica gel) column. Also 11,13-methylene derivatives of acid-and thermolabile germacranolides could be prepared in good yield with this procedure. Results obtained using alternative methods of methylenation are reported. A comparative study of the reactivity towards nucleophiles of exomethylene- and cyclopropyl sesquiterpene-γ-lactones provided little support for the involvement of compounds of the latter class in in vivo alkylation reactions.
New way to digitoxigenin from 3β-acetoxy-5-androsten-17-one. Stereoselective free radical substitution of iodide atom by nitrile group as a key step
Authors: Daniewski Andrzej Robert , Kabat Marek Michal , Masnyk Marek , Wojciechowska Wanda , Wicha Jerzy
Published: August 2009

Digitoxigenin (I) was obtained from 17-oxoandrost-5-en-3β-yl acetate (III) using, as a key step, free radical stereoselective substitution of an iodine atom in VI by a nitrile group. Transformation of the nitrile group at C-17 into a pregnane side chain or a butenolide lactone ring took place without isomerization at C-17.
Synthesis of (19E)-3,20-dioxopregn-4-en-19-al 19-(O-carboxymethyl)oxime
Authors: Fajkoš Jan , Pouzar Vladimír , Vereš Karel
Published: August 2009

Hydride reduction of the ketone I gave the (20R)-hydroxy derivative II. Cleavage of the diacetate III with zinc dust, followed by mild Jones’ oxidation led to the aldehyde V. Oximation with (O-carboxymethyl)hydroxylamine hemihydrochloride and methylation with diazomethane afforded the ester VI. Alkaline hydrolysis to the acid catalyzed rearrangement afforded the dione IX. Mild hydrolysis gave the desired hapten X derived from progesterone.
Alkaloids from Stylophorum lasiocarpum (OLIV.) FEDDE
Authors: Slavík Jiří , Hanuš Vladimír , Slavíková Leonora
Published: August 2009

From the underground part of Stylophorum lasiocarpum (OLIV.) FEDDE (0.58% alkaloids) (-)-stylopine and coptisine (as chloride IIa) were isolated as the principal alkaloids. Smaller quantities of sanguinarine, macarpine, chelerythrine, chelirubine, chelilutine (as the respective chlorides IIIa, IIIb, IIIc, IIId, IIIe) protopine, corysamine (as chloride IIb), berberine (as chloride IIc) and (-)-trans-N-methylstylopinium hydroxide (as iodide IVa) were also isolated. Chromatographically were detected small amounts of chelidonine, allocryptopine, cryptopine, scoulerine, isoboldine, magnoflorine and salt of cis-N-methylstylopinium. The aerial part (0.16% alkaloids) afforded (-)-stylopine, coptisine and (+)-chelidonine as dominant alkaloids and small amounts of protopine and (-)-cis-N-methylstylopinium hydroxide (as iodide IVb).Chromatography proved negligible amounts of sanguinarine, chelirubine, cryptopine, scoulerine, isoboldine, corytuberine, corysamine, berberine, magnoflorine and trans-N-methylstylopinium iodide. The so far undescribed 8-methoxydihydromacarpine (VIb) was prepared.
MNDO study of the [2 + 3] cycloaddition of nitroethene to formonitrile N-oxide
Authors: Barański Andrzej , Cioslowski Jerzy
Published: August 2009

Two regioisomeric pathways have been studied by MNDO method for nitroethene [2 + 3] cycloaddition to formonitrile N-oxide. It has been found that four critical structures are located along each of the pathways. Calculations indicate that both reactions take place in a concerted manner and that their transition states are early. Moreover, it was established that the path leading to 5-nitro-4,5-dihydro-1,2-oxazole is preferred.
Determination of the intensity of polychromatic radiation in the reaction compartment as a function of wavenumber
Authors: Hrdina Radim , Čepčiansky Igor , Bittová Hana
Published: August 2009

A procedure is suggested for studying the kinetics of photochemical reactions using excitation with polychromatic radiation, where the wavenumber dependence of the intensity of the polychromatic radiation entering the reaction compartment must be known. The observed relative intensities of the polychromatic source are calibrated by ferrioxalate actinometry, selected parts of the emission spectrum being eliminated by insertion of filters. The relative intensities of an HBO 200 high-pressure mercury lamp were measured. For the sake of brevity, the experimental data were fitted by a mathematical model (a polynominal), and only the parameters of the polynomial are presented in a tabular form.
The determination of N,N-dimethyl-4-aminoazobenzene and its reduction products by anodic voltammetry at a glassy carbon electrode
Authors: Barek Jiří , Pastor Tibor J. , Zima Jiří
Published: August 2009

The oxidation of N,N-dimethl-4-aminoazobenzene at a rotating and stationary glassy carbon disk electrode in a medium of 40% (v/v) acetic acid was studied in the framework of a systematic study of methods for determing the efficiency of the destruction of the genotoxic derivatives of this substance; conditions were found for the determination using direct current and differential pulse voltammetry. Analogous conditions were used to determine aniline, N,N-dimethylaniline and N,N-dimethyl-p-phenylendiamine as model substances representing possible products of the reductive splitting of genotoxic azocompounds. The determination limit of the method is less than 1 . 10-5 mol l-1 and its selectivity is completely satisfactory for controlling the efficiency of the destruction.
Effect of precipitation and aging on porous structure of aluminium hydroxide. II. Changes in pore size distributions
Authors: Roček Josef , Pospěch Roman , Weiss Jindřich , Jirátová Květuše
Published: August 2009

Differences in porous structure of the dried aluminium hydroxide (containing sulphate ions) caused by changes in temperature and pH of precipitation, the time of aging and by additions of surfactants are documented and discussed. The aluminium hydroxide precipitated at low temperatures (30 – 50°C) and pH values (7 – 8) has bi-disperse porous structure with maxima in the region of large and medium pores. The increase of temperature and pH of precipitation limits or completely suppresses medium pores and increases large and small pores. Characteristic trend was the disappearance of medium pores which led to monodispersity in the region of large and small pores. The addition of surfactants suppressed the effect of short-time aging on pore size distributions. At moderate temperatures the effect of surfactants manifested itself in the broad pore size distributions and in the increase of the volume of large and medium pores. Qualitative and quantitative differences in porous structure caused by the action of surfactants were suppressed on increasing temperature and pH of precipitation.
Cyclization and oxidation of N-substituted phenyl-N’-(2-methyl-3-phenylpropenoyl)thioureas
Authors: Dzurila Milan , Kutschy Peter , Imrich Ján , Koščík Dušan , Kraus Robert
Published: August 2009

The synthesis of 1,3-thiazines, 2-thiouracils and ureas from N-substituted phenyl-N’-(2-methyl-3-phenylpropenoyl)thioureas by intramolecular cyclization or oxidation under various conditions is described. The structure of products was verified by IR, 1H NMR and mass spectral evidence.
Preparation of 1-(2-benzimidazolyl)-2-substituted ethylene derivatives by the Wittig reaction
Authors: Prousek Josef
Published: August 2009

Article without abstract
Syntheses of β,γ-unsaturated α-amino acids
Authors: Havlíček Libor , Hanuš Jan
Published: August 2009

A review article about synthetic procedures to α-amino acids with multiple bond at β,γ-position which have been developed so far. Attention is also paid to the title syntheses of optically active products.
Synthesis of some salicylic acid derivatives and studies of their interaction with uranyl ion
Authors: Djurendić Evgenija A. , Surányi Terézia M. , Miljković Dušan A.
Published: August 2009

Some unsubstituted and substituted bis-derivatives of salicylic acid have been synthesized and their acidity constants determined spectrophotometrically in 61.10% aqueous ethanol. The stability constants of complexes these compounds from with UO22+-ion were determined spectrophotometrically using the method of continuous variation under following conditions: pH 3.58 and 3.98, 61.10% aqueous ethanol, μ = 0.5 (LiCl), 25 ± 1 °C.
2-(Biphenyl-4-yl)-5-phenyl-1,3,4-oxadiazole (PBD): Electrophilic 4’-substitution and following transformations
Authors: Kurfürst Antonín , Lhoták Pavel , Nádeník Petr , Raclová-Pavlíková Františka , Kuthan Josef
Published: August 2009

PBD was converted into 4’-substituted derivatives I-XII using usual electrophilic reagents. The decomposition of PBD, 4’-acetyl derivative I and 4’-nitro derivative VI with hydroiodic acid gave 4’-substituted 4-biphenylcarboxylic acids XIIIa-XIIIc and benzoic acid, respectively. The regioselectivity of the reaction was also proved by means of high resolution NMR spectroscopy.
Revision of the structure of 3-methoxy-14α-hydroxy-D-homo-1,3,5-(10)-estratrien-17a-one. A simple 1H NMR method for the determination of configuration of hydroxy group in position 5 and/or 14 of the D-homo-steroid skeleton
Authors: Buděšínský Miloš , Kasal Alexander , Procházka Želimír , Thoa Huynh Kim , Vašíčková Soňa , Kočovský Pavel
Published: August 2009

Eignerova and Prochazka found in 1974 the Cotton effect value for 3-methoxy-14α-hydroxy-D-homo-1,3,5(10)-estratrien-17a-one (Ia) to be Δε – 2.76.Calculation of the Δε value for this compound led, however, to a substantially lower value, which suggested the hypothesis that the compound was in fact rather an epimer with the hydroxy group in position 14β. This hypothesis was studied by means of 1H NMR spectra of synthetic models, using the changes of the chemical shifts of angular methyls, induced by in situ acylation of the angular hydroxyl with an α- or β-configuration with trichloroacetyl isocyanate (TAI). The observed TAI-acylation shifts on model compounds indicated the structure Ib with a 14b-configuration of the hydroxyl group. Indenpendent proof has been given by the synthesis of both 14-hydroxy epimers, Ia and Ib. A simple 1H NMR method is proposed for the determination of configuration of the hydroxyl in position 5 or 14 of D-homo-steroid skeleton.
Synthesis and some pharmacological properties of three new bradykinin antagonists
Authors: Lammek Bernard , Wang Yi-Xin , Gavras Haralambos
Published: August 2009

Three new analogues of bradykinin (BK) were designed, synthesized and bio assayed in conscious, unrestrained rats. The analogues were designed by modifying the [D-Arg0, Hyp3, hi5,8, D-Phe7]-BK which was previously synthesized by the Steward group and was considered to be one of the most potent antagonists of BK known to date. It has been reported herein that the introduction of additional D-Arg residue or acylation with propionic acid of the N-terminus of [D-Arg0, Hyp3, Thi5,8, D-Phe7]BK (model peptide) results in analogues with similar or weaker antagonistic potency as compared to the model, respectively. However, the acylation with 1-adamantaneacetic acid results in an analogue with more than ten times enhanced potency and efficacy. All peptides were synthesized by the solid phase method.
Reduction kinetics of bromate with thiocyanate and dynamics of the closed system BrO3-/SCN-/HClO4
Authors: Valent Ivan , Adamčíková Ľubica
Published: August 2009

The reduction kinetics of bromate ions with thiocyanate was studied polarographically and the dynamics of the BrO3-/SCN- system was studied spectrophotometrically in the medium of perchloric acid in both cases. The reduction in the presence of an at least ten-fold excess of SCN- ions is governed by the kinetics equation – d[Br(V)]/dt = a[Br(V)][SCN-][H+]2/(1 + b[SCN-]), where a = 19.2 ± 0.9 mol-3 dm9, b = 4.4 ± 0.5 mol-l dm3 at 20°C. A mechanism was proposed, based on the transfer of oxygen atom from HBrO3 to SCN- ion. The dynamic system BrO3-/SCN-/HClO4 is non-monotonous in character. According to the conditions, the production of bromine has a sigmoidal course preceded by a lag phase or the bromine concentration passes through a maximum.
Extraction of rare earth metals from trichloroacetate solutions in the presence of linear polyoxonium compounds
Authors: Vaňura Petr
Published: August 2009

Extraction of rare earth metals from lithium trichloroacetate solutions ( 1.20-2.88 mol l-1) with solutions of the commercial nonionic surfactant Slovafol 909 (p-nonylphenylnonaethylene glycol) in chloroform and dichloromethane was investigated. The extraction constants as well as the Slovafol 909 distribution constants were determined in the water-dichloromethane and water-chloroform systems. The lanthanide distribution ratios decrease with their atomic numbers first rather rapidly (approximately to Sm): the separation factor αSmLa = 1.54 and 1.87 in dichloromethane and in chloroform, respectively; for lanthanides with higher atomic numbers the drop is less pronounced (αLuLa = 2.42 and 2.85 in the two solvents, respectively).
Crystal and molecular structure of the tetracyanato-bis(phenanthroline)copper(II) complex
Authors: Jin Kim Tae , Kabešová Mária , Kožíšek Josef
Published: August 2009

At room temperature, the [Cu2(NCO)4(phen)2] complex possessed monoclinic symmetry, P21/n, with the unit cell parameters a = 0.7757(3) nm, b = 1.3563(5) nm, c = 1.1555(4) nm, β = 96.92(2)°, Z = 2. The central atom is involved in tetragonal pyramidal coordination comprising the CuN4Cu’ chromophor. The nitrogen atoms of the cyanate and phenanthroline ligands are in a square planar arrangement, from which the central copper atom is displaced in the axial direction. Through the Cu-Cu bond (0.320 nm), the [Cu(NCO)2(phen)] formula units are linked into centrosymmetric units, which in the crystal structure lie in parallel layers. The occurrence of the Cu-Cu bond can account for the fact that only one molecule of the heterocyclic ligand can be coordinated.
Selective dismantling of closo-1,2-C2B10H12 to lower-cage dicarbaborane systems
Authors: Plešek Jaromír , Štíbr Bohumil , Fontaine Xavier L. R. , Kennedy John D. , Heřmánek Stanislav , Jelínek Tomáš
Published: August 2009

A modified, high-yield synthesis of the two isomeric nido twelve-vertex [C2B10H13]- anions, "reactive" [nido-7,9-C2B10H13]- and "unreactive" [nido-7,12-C2B10H13]-, has been developed. A solution structure for the reactive [nido-7,9-C2H10B13]- isomer is proposed on the basis of the result of two-dimensional 11B and 1H correlation NMR spectroscopy. It is concluded that there is a marked similarity between this species and the eleven-vertex congener [nido-7,8-C2B9H12]-. In accord with this parallel, the "reactive" twelve-vertex species is found to undergo selective boron-vertex elimination reactions in the presence of oxidizing agents. These reactions give excellent yields of smaller-cage nido dicarbaborane compounds, namely [nido-7,8-C2B9H12]-, [9-(SMe2)-nido-7,8-C2B9H11], and nido-5,6-C2B8H12. NMR spectroscopy assigns cluster 11B and 1H resonances for all the compounds isolated, and thence permits comparison with the equivalent shielding patterns of structurally related analogues such as [nido-7-CB10H13]- and [nido-7,9-C2B9H12]-.
Normal coordinate analysis of infrared and Raman spectra of syndiotactic poly(methyl methacrylate)
Authors: Dybal Jiří
Published: August 2009

Infrared and Raman spectra of crystalline syndiotactic poly(methyl methacrylate) have been analyzed by normal coordinate calculations, using a combined valence force field transferred from branched hydrocarbons and from methyl acetate. Calculations have been done for a single chain all-trans backbone structure of syndiotactic poly(methyl methacrylate) with parallel and antiparallel side-group orientations. The infrared and Raman bands observed can be satisfactorily interpreted on the basis of the calculated potential energy distributions. The best agreement between the calculated and experimental spectra has been found for the alternate cis and trans mutual orientations of the C=O and C-CH3 bonds in subsequent monomeric units.
Kinetics of reactions of para-substituted phenyl isocyanates with amines and alcohols
Authors: Danihel Ivan , Barnikol Falk , Kristian Pavol
Published: August 2009

The reaction of para-substituted phenyl isocyanates with amines and alcohols was studied by stopped-flow method. The Hammett correlation obtained showed that the sensitivity of the above mentioned reactions toward substituent effects is the same as that of analogous reactions of phenyl isothiocyanates (ρ ~ 2). The rate constants of these reactions were found to be affected more by steric effects than by solvent effects. An one step multicentre mechanism with partial charges in transition state has been proposed for the title reactions.
Oxidation of secondary alcohols by sodium N-chlorobenzenesulphonamide in aqueous solution. A kinetic study
Authors: Mythily Chirchingi K. , Mahadevappa Dandinasivara S. , Rangappa Kanchugarakoppal S.
Published: August 2009

The kinetics of oxidation of five secondary alcohols by sodium N-chlorobenzenesulphonamide (chloramine-B) has been studied in acid medium at 40°C. The reaction is first order with respect to the oxidant and alcohol and fractional order in [H+]. The influence of added halide ions and of reaction product and the effects of varying ionic strength and dielectric constant of the medium have also been studied. The solvent isotope effects k’(H2O)/k’(D2O) were determined. The rates were studied at four different temperatures and the activation parameters were evaluated. Attempts have been made to arrive at a linear free energy relation through the Taft treatment. An isokinetic relation is observed with β = 248 K, indicating the entropy of activation as the rate controlling factor. Protonated chloramine-T (monochloramine-T) has been postulated as the reactive oxidizing species, the main product of oxidation being the corresponding ketone. A mechanism involving the interaction of protonated haloamine species and the alcohol in a rate limiting step has been proposed.
Amidinoyl isothiocyanates in the synthesis of condensed quinazolines. Preparation of 3-aryl-5,9-disubstituted s-triazolo[4,3-c]quinazolines
Authors: Špirková Katarína , Stankovský Štefan
Published: August 2009

3-Aryl-5-((4-phenyl)piperazinyl)-9-chloro-s-triazolo[4,3-c]quinazolines were prepared by an oxidative cyclization of the corresponding arylhydrazones. The IR and 1H NMR spectra of final products are presented.
Chronopotentiometric studies of certain biologically important compounds at tubular graphite electrode
Authors: Parkash Ram , Gupta Hari Om , Dutt Jatinder
Published: August 2009

The chronopotentiometric studies of certain phenothiazines in hydrodynamic systems at a solution flow-through tubular graphite electrode were carried out in sulfuric acid of different concentrations. A well-defined single wave (involving 2 electrons) in 0.1M H2SO4 and two waves (involving 1 electron each) in 2.0M H2SO4 were observed. Phenothiazines are oxidized trough the formation of a monocation radical by the elimination of one electron from the lone pair of N-atom. The monocation radical is stable in sulfuric acid of a moderate concentration and is unstable in neutral or less acidic solutions. The cation radical undergoes instantaneous hydrolysis yielding sulfoxide, thus presenting an overall two-electron oxidation of the phenothiazine derivatives. The suitability of the chronopotentiometric technique for their determination was established.
Dynamic behaviour of an extraction column with stationary continuous phase. Moments of the response to solute injection
Authors: Wichterlová Jana
Published: August 2009

Relations were derived for calculating the volumetric mass transfer coefficient from the moments of concentration response to the solute injection for the stagewise model with back flows and stationary continuous phase.
1H-1,2,4-triazole substituted β-aminoenones. β-Diones and pyrazoles as potential fungicides
Authors: Skačáni Ivan , Fišera Lubor , Bartovičová Margita , Varkonda Štefan , Hýblová Oľga
Published: August 2009

The 1-(1H-1,2,4-triazolyl)-4-amino-4-aryl-3-buten-2-ones II were synthesized from 1-((3-arylisoxazol-5-yl)methyl)-1H-1,2,4-triazoles I by alternative procedures involving treatment with molybdenum hexacarbonyl and water, or action of sodium hydridoborate in the presence of nickel disulfate, or hydrogenation. Hydrolysis of β-aminoenones II yielded β-diones III, which, on reaction with hydrazine afforded pyrazoles IV. All compounds were tested for their antifungal effect but none showed activity comparable with that of commercial preparations.
Dimethylaminomethylene protected purine H-phosphonates in the synthesis of biologically active RNA (24-mer)
Authors: Arnold Luboš , Smrt Jiří , Zajíček Jaroslav , Ott Günther , Schiesswohl Michael , Sprinzl Mathias
Published: August 2009

Preparation of 5’-O-(4,4’-dimethoxytrityl)-2’-O-tert-butyldimethylsilyl (tBDMSi) derivatives of N2-dimethylaminomethyleneguanosine (IIIa) and N6-dimethylaminomethyleneadenosine (IVa) and their 3’-H-phosphonates (IIIb, IVb) is described. The compounds IIIb and IVb together with corresponding derivatives of uridine (Vb) and N4-benzoylcytidine (VIb) were used as synthones in machine assisted synthesis of microhelixAla (5’-GGGGCUAUAGCUCUAGCU.CCACCA-3’) (X). The compound X was aminoacylated by means of alanyl-t-RNA synthetase (E.coli).
Synthesis of 8,11-dihydro-10-methyl-8,11-diphenylpyrazolo[4’,3’:5,6]pyrano[3,2-e][1,2,4]-triazolo[1,5-c]pyrimidine and some derivatives
Authors: Abd Elmonem Maisa E. , Younes Mansour I. , Metwally Saoud A. , Atta Aly H.
Published: August 2009

Article without abstract
1H and 13C NMR spectra of 2,2’-disubstitutedtrans-azobenzenes suitable for preparation of metallized azo dyes
Authors: Jirman Josef
Published: August 2009

The 1H and 13C NMR spectra have been measured of six trans-azobenzenes substituted at 2 and 2’ positions with substituents favourable for complex formation with a metal (OH, NH2, NHCOCH3, COOH). From the standpoint of NMR such substituted trans-azobenzenes are present in solution in a rapid equilibrium following from rotation around the bond between C-1 of phenyl group and N atom of azo linkage. The predominant form has the substituent in the syn-position with respect to the free electron pair of the nearer azo nitrogen atom. The equilibrium is affected by dipolar aprotic solvents (such as hexadeuteriodimethyl sulfoxide) by decreasing the presence of the predominant form by 1 to 11%.
Synthesis of (Z)-1,8- and (E)-1,8-pentadecadiene: Tumor inhibitors
Authors: Vig Rakesh , Sabharwal Arun , Singh Jasvinder
Published: August 2009

Syntheses of (Z)-1,8- and (E)-1,8-pentadecadienes have been achieved trough Wittig, Claisen ortho ester rearrangement and Li2CuCl4 catalysed coupling reactions.
5,13-Diethyl-10-methyl-8-heptadecanone: A component of post-1976 Kelex 100
Authors: Striegel Hans-Günter , Wiegrebe Wolfgang
Published: August 2009

The title compound was prepared by mixed aldol condensation of 2-ethylhexanal and acetone, double bond hydrogenation, aldol autocondensation of the resulting saturated ketone and finel double bond hydrogenation. It is identical with the ketone C22H44O previously isolated from new Kelex 100 which was erroneously assigned a furoquinoline structure.
Synthesis and biological properties of cholecystokinin heptapeptide analogues containing D- and L-forms of tert-leucine or neopentylglycine in position 5
Authors: Hlaváček Jan , Pírková Jana , Pospíšek Jan , Slaninová Jiřina , Maletínská Lenka
Published: August 2009

Using solution or solid-phase synthesis we prepared the cholecystokinin fragment Boc-CCK-7 (Boc-Tyr-(SO3-.Na+)-Met-Gly-Trp-Met-Asp-PheNH2) and its four analogues in which the methionine moiety (Met) in the carboxy-terminal part is replaced by tert-leucine (Tle) or neopentylglycine (Neo) residue or D-enantiomers of these non-coded amino acids. These structural modifications led to reduction of the studied biological activities (gall bladder contraction, anorectic activity, analgetic and sedation activity) of all prepared analogues except Boc[Neo5]-CCK-7 which, being less analgetically active, retains full gall bladder and sedation activity of CCK-8. Moreover, its anorectic activity is substantially higher (400%). This analogue is very interesting particularly for its selectively increased (4x) anorectic effect compared with that of CCK-8.
Kondensationsreaktionen von 2-formyl-1,6-methano[10]annulen
Authors: Niedlein Richard , Winkler Ralf
Published: August 2009

2-Formyl-1,6-methano[10]annulen (1) reagiert mit 1,3-Dioxan-2-yl-methyltriphenylphosphoniumbromid zu 2-(1,6-Methano[10]annulen-2-yl)propenal (2). Aldehyd 1 reagiert unter TiCl4-Zink-Katalyse zu 1,2-Bis-(1,6-methano[10]annulen-2-yl)-ethen 3a, und Vinyloge 2 zu 1,6-Bis-(1,6-methano[10]annulen-2-yl)-hexa-1,3,5-trien 3b. Wahrend sich sowohl 1 als auch 2 in ihre 2,4-Dinitrophenylhydrazone 4a und 4b uberfuhren lassen, gelingt nur im Falle des aliphatischen Aldehydes 2 die Reaktion zum N-Methylbenzthiazolinonhydrazon 5. Aldehyd 1 reagiert jeweils unter Baseneinwirkung mit N-Methyliodiden aromatischer 2-Methyl- und 4-Methyl-Azaheterocyclen zu den Stilbazolderivaten 6a-6f, mit Malonsauredinitril zu 1,1-Dicyano-2-(1,6-methano[10]annulen-2-yl)ethen 7, mit Tetraiodmethan zu 1,1-Diiod-2-(1,6-methano[10]annulen-2-yl)-ethen 8 und mit Nitromethan zu 1-(1,6-Methano[10]annulen-2-yl)-2-nitroethen 9.
Unusual formation of sterically hindered primary amines in a series of pyrrolo- and pyrido[1,2-a]indoles
Authors: Jirkovsky Ivo , Greenblatt Lynne , Baudy Reinhardt
Published: August 2009

2,3-Dihydro-2,2,9-trimethyl-1H-pyrrolo[1,2-a]indol-1-amine and its 1-(1-pyrrolidinyl) analog have been synthesized from the corresponding 1-ol via mesylation in pyridine followed by treatment with pyrrolidine. Mechanisms of the former, unexpected amination are briefly discussed. Evidence is presented that the pyridine ring serves as a masked amino group. The phenomenon is partly attributed to steric congestion. Similar preparation of 2-bromo-6,7,8,9-tetrahydro-8,8,10-trimethylpyridol[1,2-a]indol-9-amine supports this notion.
On equilibration of quassin and 4-epiquassin
Authors: Stojanac Nada , Valenta Zdenek
Published: August 2009

Equilibration of quassin and 4-epiquassin is described. Various quassin derivatives are characterized and their relationship to quassin (I) is discussed. A regioselective deprotonation is achieved in quassin and 4-epiquassin (III) by the introduction of a diosphenolate grouping which makes a potentially acidic H-atom unavailable for attack by base.
Reinvestigation of heterocyclic structures: Oxidation products from 1-substituted 2,4,6-triphenylpyridinium salts
Authors: Böhm Stanislav , Kubík Richard , Novotný Jiří , Ondráček Jan , Kratochvíl Bohumil , Kuthan Josef
Published: August 2009

Ferricyanide oxidation of pyridinium salts Ia, Ib leads to mixture of isomeric heterocyclic ketones IIa, IIb and IVa, IVb, respectively. Crystal and molecular structures of the products IIb and IVb were determined by X-ray diffraction analysis. Formely presumed formation of heterocyclic systems type of the III type has been corrected.
Antimycobacterial derivatives of tetrazole
Authors: Waisser Karel , Vanžura Jiří , Hrabálek Alexandr , Vinšová Jarmila , Grešák Štefan , Hruška Jiří , Odlerová Želimíra
Published: August 2009

A synthesis of (1-phenyltetrazol-5-ylthio)acetic acid derivatives has been developed. Functional variations concern the carboxylic group and/or the 4 position of phenyl group. Most of the compounds prepared have been tested with regard to their antimycobacterial activity but the activities found are medium or low ones. However, (1-phenyltetrazol-5-ylthio)acetic acid is better than the antituberculotic isoniazid in the activity to Mycobacterium avium.
Relations between structure and antituberculotic activity in a group of 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins
Authors: Waisser Karel , Bořková Jana
Published: August 2009

Relations between chemical structure and activity to Mycobacterium tuberculosis have been looked for within a group of the derivatives of 10-piperazino-10,11-dihydrodibenzo[b,f]thiepins prepared by Protiva et al. It has been found that the most reliable results are obtained with application of the model by Free and Wilson. The activity can be considered additive with regard to the contributions of the molecular segments varied.
Search for new analeptics: Homoanalogues of dimefline-type derivatives
Authors: Carrara Maria , Capolongo Francesca , Cima Lorenzo , Fabbri Giuseppina , Rampa Angela , Valenti Piero , Da Re Paolo
Published: August 2009

The preparation and the pharmacological profile of a selected number of homologues at C2 (homoflavones) of dimefline-type analeptics are described. The structural modifications introduced in I seems to cause a remarkable alteration of the CNS stimulating pattern so that the new compounds are to be considered as minor analeptics.
Synthesis of pyridyl isosteres of thioperamide as H3-receptor histamine antagonists
Authors: Ganellin C. Robin , Jayes Dalia , Khalaf Yasmin S. , Tertiuk Wasyl , Arrang Jean-Michel , Defontaine Nadia , Schwartz Jean-Charles
Published: August 2009

The synthesis and evaluation as H3-receptor histamine antagonists is described of novel isoteric analogues of thioperamide. The compounds are designed to have fewer NH groups in order to assist brain penetration. However none of the compounds is sufficiently active as an antagonist in vitro. The 2-pyridyl analogue II has Ki = 13 μmol 1-1.
Potential antidepressants: 2-(fluoro-, chloro-, bromo- and cyanophenylthio)benzylamines as inhibitors of 5-hydroxytryptamine and noradrenaline re-uptake in brain
Authors: Kmoníček Vojtěch , Pomykáček Josef , Holoubek Jiří , Svátek Emil , Valchář Martin , Metyšová Jiřina , Polívka Zdeněk
Published: August 2009

2-, 3- and 4-Fluorothiophenol, 2-, 3- and 4-chlorothiophenol, and 2-bromothiophenol were converted in two steps into the corresponding 2-(halogenphenylthio)benzoyl chlorides IV which afforded amides V and VI by reaction with dimethylamine and N,N,N’-trimethylethylenediamine. The amides were reduced either by lithium aluminium hydride or by diborane to benzylamines Ia-Ig and IIa-IIc. The reaction of 2-chlorobenzaldehyde with 3-bromothiophenol or 4-bromothiophenol afforded aldehydes VIIh and VIIi yielding subsequently benzylamines Ih and Ii by subsequent reducing amination. Cyano analogs Ij and Il were obtained from the bromo derivatives Ig and Ii by their reaction with cuprous cyanide in hexamethylphosphoric triamide. The synthesis of compound Ik was effected via aldehyde acid VIIm affording amino acid Im on reducing amination. The conversion of the latter to amide In and its dehydration yielded nitrile Ik. Some of the compounds synthesized, especially Ic, Id, Ie and If, are efficient and selective inhibitors of re-uptake of 5-hydroxytryptamine in brain structures. The most interesting from this aspect is compound If(hydrochloride VUFB-17649) of this series which was chosen for detailed pharmacological testing.
Fifty years in chemical drug research
Authors: Protiva Miroslav
Published: August 2009

Article without abstract
Heat capacities of liquid 2,3,6-trimethylpyridine, 2,4,6-trimethylpyridine and 3-methoxypropionitrile within the range of temperatures of 300 to 328 K
Authors: Svoboda Václav , Zábranský Milan
Published: August 2009

Molar heat capacities of 2,3,6-trimethylpyridine, 2,4,6-trimethylpyridine and 3-methoxypropionitrile in the liquid state were measured at the constant atmospheric pressure in the temperature interval of 300.60 to 328.35 K. The static type of adiabatic calorimeter was used for the measurements.
The determination of 4-substituted derivatives of N-nitroso-N-methyl aniline by fast scan differential pulse voltammetry at a hanging mercury drop electrode
Authors: Barek Jiří , Mejstřík Viktor , Švagrová Ivana , Zima Jiří
Published: August 2009

Optimum conditions were found for the determination of N-nitroso-N-methyl aniline and its derivatives substituted in the 4 position by -CH3, -OCH3, -Cl, -CN, -OH or -NO2 groups by fast scan differential pulse voltammetry at a hanging mercury drop electrode in the concentration range 1 10-5-2 10-7 mol l-1. It was demonstrated that these techniques are useful for the analysis of a mixture of the test substances either directly or after separation by thin-layer chromatography and that false positive results can be eliminated by UV irradiation of the test sample. An attempt to further increase the sensitivity by adsorptive accumulation of the test substances on the surface of the hanging mercury drop electrode was not successful as the test N-nitroso compounds are practically not adsorbed on this electrode.
Reactivity of phenylsulfonyl isothiocyanates and transfer of substituent effects through the sulfonyl group
Authors: Suchár Gejza , Hritzová Oľga , Imrich Ján , Jasovská Antónia
Published: August 2009

Kinetics of nucleophilic additions of butylamine to phenylsulfonyl isothiocyanate was investigated by the stopped-flow UV spectroscopic method and the transfer of electronic effects of substituents on the reaction centre through the SO2 group was examined. The structure and the polar character of SO2NCS, NCS and SO2 groups is discussed.
Derivatives of 5α-androstan-3α- and 3β-ol with acrylonitrile side chain
Authors: Pouzar Vladimír , Chodounská Hana , Černý Ivan , Drašar Pavel
Published: August 2009

Aldehydes II - III were reacted with diethyl cyanomethylphosphonate and sodium hydride in 1,2-dimethoxyethane to give the respective pairs of unsaturated nitriles IVa and Va, VIa and VIIa, and VIIIa and IXa differing in configuration at the 20(21)-double bond. The pure isomers were obtained by chromatography on alumina, and the configuration at the double bond in them has been established on the basis of the coupling constants J(20, 21) in their 1H NMR spectra. Nitriles IVa - VIIa and IXa were converted via the corresponding hydroxy derivatives into hemisuccinates IVd - VIId and IXd, and into β-D-glucosides IVe - VIIe and IXe.
Functionalization of 3β,28-lupanediol diacetate with chromium(VI) oxide
Authors: Sejbal Jan , Klinot Jiří , Buděšínský Miloš , Protiva Jiří
Published: August 2009

The oxidation of 3β,28-lupanediol diacetate (I) with chromium(VI) oxide gives low yields of products with functional groups in the ring E as products of hydroxylation at the 19β position (IV, VI, and IX) and the 11-ketone VII which has been transformed into other lupane derivatives with an oxygen functional group at 11 position (VIII, XIII - XV) or with a 9(11)-double bond (XVI, XVII). Structure of the compounds prepared has been verified by their 1H and 13C NMR spectra as well as by their mass spectra.
Defensive substances from the frontal gland secretion of Nasutitermes nigriceps termite soldiers
Authors: Valterová Irena , Buděšínský Miloš , Vrkoč Jan
Published: August 2009

The components of the defence secretion of the soldiers of Nasutiterms nigriceps termite species (Isoptera: Termitidae: Nasutitermitinae) have been identified. In the volatile fraction the following components were found: α- and β-pinene, camphene, myrcene, α-terpinene, p-cymene, limonene and terpinolene. Ten diterpenic compounds (I - X), mostly derivatives of the tricyclic trinervitane, were found in the non-volatile fraction. The structure of the so far undescribed 1(15),8(19)-trinervitadiene-2β,3α,14α-triol triacetate (X) was determined on the basis of its mass and infrared spectra and a detailed analysis of 1H and 13C NMR spectra. Considerable differences were found in the composition of the non-volatile fraction of the secretion of the species of termites studied from various localities.