Collection of Czechoslovak Chemical Communications

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ISSN / EISSN : 0010-0765 / 1212-6950
Total articles ≅ 19,428
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Han Wang, Rui Wang
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1595-1605; https://doi.org/10.1135/cccc2011058

Abstract:
Clean fuel and clean production technologies, including desulfurization, have become a subject of concern in environmental catalysis studies. One of the most promising desulfurization processes is oxidative desulfurization combined with extraction. Keggin-type heteropoly acids encaged Y-type zeolite were studied as promising catalytic agents for the oxidation of dibenzothiophene with hydrogen peroxide in a normal octane/acetonitrile biphasic system. The key factors affecting the reaction, including the catalyst amount, O/S molar ratio and contact time between oxidant and catalyst, were investigated. The conditions favourable to the reaction were also determined. Moreover, the reused encaged type catalyst exhibited good catalytic activity in recovery experiments and can be effectively applied to diesel oil.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1579-1594; https://doi.org/10.1135/cccc2011039

Abstract:
An enantioselective synthesis of a C ring of taxol has been accomplished. The key step is an oxidative cleavage of a derivative of the Wieland–Miescher ketone. A first attempt of a Shapiro reaction modelling the coupling of the C ring with the A fragment of taxol was also successful.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1567-1577; https://doi.org/10.1135/cccc2011101

Abstract:
The hydrogen-to-deuterium isotope exchange reaction of hydrogen in position 5 of pyrimidine derivatives was studied using NMR techniques. The dependence of the reaction rate on the pH and on the solvent composition was explored. In tracer experiments using tritiated water, the application of this exchange reaction was tested for the preparation of pyrimidine derivatives labeled by tritium.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1549-1566; https://doi.org/10.1135/cccc2011152

Abstract:
We report on the preparation of novel 1′-homonucleoside derivatives locked in a West conformation by 1′,4′-bridge consisting of annulated benzene or naphthalene ring. The crucial step of the synthesis was Diels–Alder reaction of an appropriate aryne with a suitable furane derivative. Antiviral properties of novel compounds were studied and slight activity against HCV was detected in several compounds.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1529-1548; https://doi.org/10.1135/cccc2011156

Abstract:
The nitration of eugenol was investigated by using density functional theory (DFT) calculations. Potential energy surface and molecular electrostatic potential of eugenol was constructed in order to find, respectively, the minimum energy conformers and the possible sites for electrophilic attack. Stationary points were located and characterized at the B3LYP/6-311++G(2d,2p) level of theory. A strongly bound π-complex was found, in which the distance between the nitrogen atom of the NO2 moiety and the C1 carbon atom of the aromatic ring is 2.15 Å in the gas phase and 2.06 Å in dichloromethane. The most favorable σ-complex or Wheland intermediate is the result from the interaction between the nitrogen and the C6 ring carbon atom. The transition state that connects both complexes is more resembling the σ-complex. The nitronium ion exothermically reacts with eugenol to give the π-complex without an energy barrier. The next stage of the reaction pathway, π-complex → σ-complex, is endothermic and involves a Gibbs energy of activation of 7.9–8.0 kcal mol–1 (gas phase) and 8.3–8.9 kcal mol–1 (CH2Cl2).
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1509-1527; https://doi.org/10.1135/cccc2011166

Abstract:
Cellulose fibres were employed as reinforcement agent for biodegradable composites using polylactic acid (PLA) as a polymer matrix. PLA can be obtained from renewable resources, and it is attracting much interest owing to its favourable physico-mechanical properties and biodegradability. Prior to composite compounding, two commercial PLA from different suppliers were characterized for apparent density, flow index, crystallinity, thermal properties, melt flow rheology and intrinsic viscosity for comparison. In experiments performed with an integrated compounding–injection moulding machine (ICIM), the effects of the processing conditions on the mechanical properties of composites (tensile strength, stiffness and strain at break) were analyzed using a Taguchi experimental design. Other properties of the composites, such as surface morphology and fibre length distribution, were also considered. ICIM technology provided composites with better mechanical properties and lower fibre degradation than the conventional sequential extrusion and injection moulding (SEIM) technology.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1487-1527; https://doi.org/10.1135/cccc2011176

Abstract:
While direct Sonogashira coupling of 6-halopurines with methyl propiolate and with propargyl aldehyde was not successful, the corresponding orthoester and propargyl aldehyde diethylacetal reacted smoothly. Such prepared orthoester was then converted to the desired methylester by methanolysis, the acetal was too stable to be hydrolyzed. The obtained 6-ethynylpurines, bearing orthoester, acetal, methoxycarbonyl and for comparison also the phenyl substituent on the ethynyl group, were subjected to the cycloaddition reaction with cyclopentadiene, diazomethane and phenylazide. Electron deficient alkynylpurines were considerably more reactive in this reaction compared to the not activated phenylethynyl derivative. The prepared alkynylpurines exhibited medium cytostatic activity (IC50 = 2.6–15 μM), while the cycloadducts were inactive.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1471-1486; https://doi.org/10.1135/cccc2011090

Abstract:
The condensation of the 5′-O-DMT-3′-deoxy-3′-aminothymidine with 3′-O-TBDMS-thymidine- 5′-aldehyde, followed by reduction of the resultant imine derivative and removal of tert-butyldimethylsilyl (TBDMS) protecting group, provided a dimer (denoted as TNHT), which is a congener of dithymidine phosphate with the phosphate linkage 3′-O-P(O)(OH)-O-5′ replaced with an amino group (–NH–). After phosphitylation of the 3′-OH group, the dimer TNHT was introduced (by the standard phosphoramidite approach) into a central part of the nonadecathymidylate. This oligomer exhibited lower affinity to the complementary single and double stranded DNA complements as compared to unmodified T19 oligonucleotide. The cleavage of modified oligomer with the snake venom and calf spleen phosphodiesterases was completely suppressed at the site of modification. RNA oligomers containing the TNHT dimer were used for preparation of siRNA molecules directed towards mRNA of BACE1 (beta-site amyloid precursor protein cleaving enzyme). The presence of the TNHT units at the 3′-ends of the RNA strands of the siRNA molecule (the siRNA itself is an effective gene expression inhibitor for BACE1) preserved the gene silencing activity and improved the stability of the modified siRNA in 10% fetal bovine serum.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1447-1469; https://doi.org/10.1135/cccc2011070

Abstract:
Using generated conformations from docking analysis by CDOCKER algorithm, some 3D-QSAR models; CoMFA region focusing (CoMFA-RF) and CoMSIA have been created on a series of a new class of potent and non-chiral renin inhibitors. The satisfactory predictions were obtained by CoMFA-RF and CoMSIA based on docking alignment in comparison to CoMFA. Robustness and predictability of the models were further verified by using the test set, cross validation (leave one out and leave ten out), bootstrapping, and progressive scrambling. All-orientation search (AOS) strategy was used to acquire the best orientation and minimize the effect of the initial orientation of aligned compounds. The results of 3D-QSAR models are in agreement with docking results. Moreover, the resulting 3D CoMFA-RF/ CoMSIA contour maps and corresponding models were applied to design new and more active inhibitors.
Collection of Czechoslovak Chemical Communications, Volume 76, pp 1433-1445; https://doi.org/10.1135/cccc2011109

Abstract:
Electrochemical impedance spectroscopy (EIS) was used for characterization of electron transfer in various redox probes, such as the redox couple ferrocyanide-ferricyanide, ferrocene, ferrocenemethanol, and the poly(3,4-ethylenedioxythiophene) (PEDOT) conducting polymer containing gold nanoparticles. The PEDOT coating was deposited onto platinum (Pt) and glassy carbon (GC) electrodes by galvanostatic electrochemical polymerization from an aqueous solution containing 10–2 M EDOT and 10–1 M LiClO4 as supporting electrolyte. The PEDOT-Au nanoparticles composite coating was prepared by droplet deposition of Au nanoparticles on top of the Pt/PEDOT and GC/PEDOT modified electrodes. The pure PEDOT and PEDOT-Au nanoparticles composite coatings were investigated using EIS and cyclic voltammetry (CV) in 10–1 M LiClO4 solution containing various redox probes. The impedance spectra were recorded at the formal redox potential of the redox probes. The charge transfer resistance (Rct), solution resistance (Rs), exchange current density (i0), standard rate constant (k0), and double-layer capacitance (Cdl) were calculated from the EIS data.
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