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31.
Koshkin AA 《The Journal of organic chemistry》2004,69(11):3711-3718
Second generation 2'-O,4'-C-methylene-linked nucleotides 1-3 containing hypoxanthine, 2,6-diaminopurine, and 2-aminopurine nucleobases were synthesized and incorporated into locked nucleic acid (LNA) oligonucleotides by means of the automated phosphoramidite method. The required phosphoramidite monomeric units were efficiently prepared via convergent synthesis. The glycosyl donor 4 was stereoselectively coupled with hypoxanthine and 6-chloro-2-aminopurine to give the 4'-C-branched nucleosides 5 and 17. The methods for conversion of 5 and 17 into phosphoramidites 11, 25, and 29 were developed and described in full details for the first time. Hybridization properties of LNA octamers containing the new LNA nucleotides were assessed against perfect and singly mismatched DNA. The binding studies revealed that all LNA octamers hybridize very efficiently to DNA following Watson-Crick base-pairing rules with increased binding affinity compared to the DNA analogues. The unique properties of the nucleotides 1-3 make them very useful for further strengthening of the LNA technology. 相似文献
32.
[reaction: see text] A unique new set of reactions has been observed in heterocyclic photochemistry. 2-Methyl-4,4-diphenyl-3,4-dihydropyrimidin-1(2H)-one has been synthesized and its photochemistry investigated. This compound has been found to lead to a rearranged, dimeric product arising from a unique bond-scission process. 相似文献
33.
D. G. Belov Yu. A. Ol'khov G. P. Belov T. I. Solovyeva G. I. Kozub 《Journal of Thermal Analysis and Calorimetry》1996,46(1):237-243
Polyacetylene films irradiated by-rays up to 100 MRad were studied by means of TMA, DTG and DSC methods.It is shown that as the irradiation dose increases the concentration of topological branching knots into the polymer chains and theT
g values decrease, the total mass loss and the enthalpy of the thermal isomerization reaction also decrease. 相似文献
34.
V. P. Belov 《Theoretical and Mathematical Physics》1994,101(1):1254-1268
Groups of spacetime transformations of the second class are constructed. It is shown that the minimum group of spacetime transformations that satisfy the principles of the special theory of relativity isD=P(2,4)O(2,4)O(1,3).D. V. Efremov Institute of Electrophysical Apparatus. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 101, No. 1, pp. 136–157, October, 1994. 相似文献
35.
Zhdankin VV Kuehl CJ Krasutsky AP Bolz JT Simonsen AJ 《The Journal of organic chemistry》1996,61(19):6547-6551
Organosulfonyloxy derivatives of 1,2-benziodoxol-3(1H)-one (3a-c) and 3,3-bis(trifluoromethyl)-3(1H)-1,2-benziodoxole (5a-c) can be prepared in high yield by the reaction of 1-hydroxybenziodoxoles 1 or 4 and the corresponding sulfonic acids or Me(3)SiOTf in the form of stable, but moderately hygroscopic, microcrystalline solids. Reaction of the triflate derivatives 3a and 5a with alkynyltrimethylsilanes affords either alkynyliodonium triflates 6, or (E)-beta-(trifluoromethanesulfonyloxy)alkenyliodonium triflates 7, while the same reaction in the presence of pyridine selectively gives the respective 1-alkynylbenziodoxoles 8 and 9 in 82-90% yield. 相似文献
36.
V. I. Zhukov G. V. Val’kovich B. N. Skorik Yu. M. Petrov G. P. Belov 《Russian Journal of Applied Chemistry》2007,80(7):1195-1200
Analysis of mass and heat balance in the reaction node of the process of ethylene dimerization into but-1-ene under the industrial
conditions is performed. It is found that ethylene concentration in the reactor liquid phase by a complex way depends on the
reactor temperature, pressure and but-1-ene concentration in the liquid phase. Optimal process temperature is 80–90°C, operating
pressure in the reactor is 0.6–0.8 MPa. Increase in pressure above 1 MPa practically excludes heat withdraw via but-1-ene
evaporation and makes the system of heat withdrawing ineffective. 相似文献
37.
Sergei V. Kostjuk Alexei Yu. Dubovik Irina V. Vasilenko Alexander N. Frolov Fyodor N. Kaputsky 《European Polymer Journal》2007,43(3):968-979
The cationic polymerization of styrene with the 2-phenyl-2-propanol (CumOH)/AlCl3 · OBu2 initiating system at various dibutyl ether concentrations in a mixture of 1,2-dichloroethane and n-hexane (55:45 v/v) at −15 °C was investigated. The experimental results showed that an increase in dibutyl ether concentration leads to a noticeable decrease in the polymerization rate as well as to the more controlled polymerization in terms of molecular weight (Mn) and molecular weight distribution (MWD) evolutions. The kinetic investigation revealed that the polymerization proceeds in two stages. The first stage is characterized by high polymerization rate and slow initiation relative to propagation. During this stage molecular weight decreases or does not change and MWD increases with conversion. In the second stage considerably slower quasiliving polymerization of styrene occurs. The quasiliving nature of the styrene polymerization by the CumOH/AlCl3 · OBu2 system is proved and mechanistic scheme of the polymerization is proposed. 相似文献
38.
Kolen'ko YV Kovnir KA Gavrilov AI Garshev AV Meskin PE Churagulov BR Bouchard M Colbeau-Justin C Lebedev OI Van Tendeloo G Yoshimura M 《The journal of physical chemistry. B》2005,109(43):20303-20309
Mesoporous nanosized TiO2 and Zn(x)Ti(1-x)O(2-x) solid solution having a Zn content below 10 mol % with a particles size between 13 and 17 nm are prepared by a template-free sol-gel method followed by high-temperature supercritical drying in 2-propanol. The structural, textural, and electronic properties of the obtained nanomaterials are methodically investigated by using XRD, SEM, TEM, ED, HREM, EDX, ICP-OES, N(2) adsorption-desorption, Raman spectroscopy, and diffuse reflectance UV-vis spectroscopy. It is shown that the proposed synthesis technique leads to the formation of a Zn(x)Ti(1-x)O(2-x) solid solution based on the anatase crystal structure rather than a two-phase sample. High-resolution electron microscopy and electron diffraction indicate that the distribution of zinc atoms over the anatase structure does not lead to a considerable deformation of the crystal structure. 相似文献
39.
Core-shell nanostructures from single poly(N-vinylcaprolactam) macromolecules: stabilization and visualization 总被引:1,自引:0,他引:1
Bronstein LM Kostylev M Tsvetkova I Tomaszewski J Stein B Makhaeva EE Okhapkin I Khokhlov AR 《Langmuir : the ACS journal of surfaces and colloids》2005,21(7):2652-2655
Formation of core-shell poly(N-vinylcaprolactam) (PVCL) single-molecule nanostructures due to interaction of PVCL with metal ions was studied using transmission electron microscopy, 13C NMR, and light scattering. This study demonstrates that addition of CoCl2 to PVCL in its globular conformation yields unimolecular core-shell polymer particles with the core decorated with Co(II) ions. The crucial condition for formation of well-defined unimolecular nanostructures is the presence of stable globular aggregates in aqueous solution. Moreover, the metal ions should have a sufficiently high coordination number (higher than 2) to provide a cross-linking and stabilization of the core. 相似文献
40.
V. I. Kelarev V. N. Koshelev N. V. Belov O. V. Malova R. A. Karakhanov 《Chemistry of Heterocyclic Compounds》1994,30(2):218-221
6-Substituted 2,4-bis(trichloromethyl)-sym-triazet:es containing the 2,6-di-tert-butylphenol group are synthesized by simultaneous cyclotrimerization of trichloroacetonitrile with the nitrile or thiocyanate derivative of the sterically hindered phenol in the presence of gaseous HCl. Significant amounts of 2,4,6-tris(trichloromethyl)-sym-triazene are formed as a byproduct.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 240–243, February, 1994. Original article submitted January 19, 1994. 相似文献