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111.
Georgii V. Bobkov Sergey N. Mikhailov Arthur Van Aerschot Piet Herdewijn 《Tetrahedron》2008,64(27):6238-6251
A simple and efficient method for the preparation of eight phosphoramidite building blocks for incorporation of 2′-O-(2-aminoethoxymethyl)ribonucleosides and 2′-O-(3-aminopropoxymethyl)ribonucleosides into synthetic oligonucleotides has been developed. The synthetic routes are maximally convergent and provide sufficient amounts of phosphoramidites for several solid-phase synthesis coupling reactions. Using acyclic derivatives 17a,b the overall yields of phosphoramidites 2 and 3 were increased up to 50% for pyrimidine nucleosides and up to 30% for purine derivatives with substantial decrease of total reaction steps. The 2′-O-substituent was found to be stable during oligonucleotide synthesis. The resulting oligonucleotides are of particular interest for post-synthetic functionalization and conjugation. 相似文献
112.
Sergey Chervon 《General Relativity and Gravitation》2004,36(7):1547-1553
A new strategy of exact solutions construction in inflationary cosmology within the self-interacting scalar field theory is proposed. It is shown that inflationary models have no restrictions dictated by the slow-roll approximation on the self-interacting potential. The suggested approach makes it possible to compute precisely the e-folds numbers in inflationary scenarios. The scalar field with a logarithmic evolution in time is analyzed in details. Other possible types of scalar field evolution are discussed. 相似文献
113.
Peter Nockemann Dr. Ben Thijs Dr. Kyra Lunstroot Dr. Tatjana N. Parac‐Vogt Prof. Dr. Christiane Görller‐Walrand Prof. Dr. Koen Binnemans Prof. Dr. Kristof Van Hecke Dr. Luc Van Meervelt Prof. Dr. Sergey Nikitenko John Daniels Dr. Christoph Hennig Dr. Rik Van Deun Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2009,15(6):1449-1461
The dissolution process of metal complexes in ionic liquids was investigated by a multiple‐technique approach to reveal the solvate species of the metal in solution. The task‐specific ionic liquid betainium bis(trifluoromethylsulfonyl)imide ([Hbet][Tf2N]) is able to dissolve stoichiometric amounts of the oxides of the rare‐earth elements. The crystal structures of the compounds [Eu2(bet)8(H2O)4][Tf2N]6, [Eu2(bet)8(H2O)2][Tf2N]6?2H2O, and [Y2(bet)6(H2O)4][Tf2N]6 were found to consist of dimers. These rare‐earth complexes are well soluble in the ionic liquids [Hbet][Tf2N] and [C4mim][Tf2N] (C4mim=1‐butyl‐3‐methylimidazolium). The speciation of the metal complexes after dissolution in these ionic liquids was investigated by luminescence spectroscopy, 1H, 13C, and 89Y NMR spectroscopy, and by the synchrotron techniques EXAFS (extended X‐ray absorption fine structure) and HEXS (high‐energy X‐ray scattering). The combination of these complementary analytical techniques reveals that the cationic dimers decompose into monomers after dissolution of the complexes in the ionic liquids. Deeper insight into the solution processes of metal compounds is desirable for applications of ionic liquids in the field of electrochemistry, catalysis, and materials chemistry. 相似文献
114.
leg . Varzatskii Yan Z. Voloshin Sergey V. Korobko Sergey V. Shulga Roland Krmer Alexander S. Belov Anna V. Vologzhanina Yurii N. Bubnov 《Polyhedron》2009,28(16):553
The nucleophilic substitution of the reactive halogen atoms of clathrochelate precursors with soft nucleophilic agents was promoted by cadmium(II) ion using various types of cadmium-containing compounds. Cadmium(II) activates the C–Hal bond both by the coordination of halogen substituents to this ion and the formation of anionic forms of a nucleophilic agent with cadmium amides, that increase the electron density on a reactive site of this agent. The cadmium-promoted substitution reactions of the reactive chlorine ribbed substituents in the di- and hexachlorine-containing clathrochelate precursors afforded the clathrochelate ribbed-functionalized derivatives of soft nucleophiles [alcohols (including fluorinated ones) and aromatic amines (including the nucleophiles with electron-withdrawing substituents)] by efficient one-pot procedures in high yields under mild conditions with generated in situ low-basic cadmium(II) alcoholates and amides. The complexes obtained were characterized using elemental analysis, MALDI-TOF mass spectrometry, IR, UV–Vis, 57Fe Mössbauer, and NMR spectroscopies, and X-ray crystallography. The potential of cadmium-promoted reactions for synthesis of different types of organic and coordination compounds is discussed. 相似文献
115.
Ignat'eva DV Goryunkov AA Tamm NB Ioffe IN Avdoshenko SM Sidorov LN Dimitrov A Kemnitz E Troyanov SI 《Chemical communications (Cambridge, England)》2006,(16):1778-1780
Two isomers of C70(CF3)12 have been isolated from a mixture obtained by trifluoromethylation of C70 with CF3I; their molecular structures determined by X-ray crystallography are in good agreement with the results of theoretical DFT calculations for the most stable C70(CF3)12 isomers. 相似文献
116.
Gaspar AB Ksenofontov V Reiman S Gütlich P Thompson AL Goeta AE Muñoz MC Real JA 《Chemistry (Weinheim an der Bergstrasse, Germany)》2006,12(36):9289-9298
The crystal structure of the complex [{Fe(bt)(NCS)(2)}(2)bpym] (1) (bt=2,2'-bithiazoline, bpym=2,2'-bipyrimidine) has been solved at 293, 240, 175 and 30 K. At all four temperatures the crystal remains in the P space group with a=8.7601(17), b=9.450(2), c=12.089(3) A, alpha=72.77(2), beta=79.150(19), gamma=66.392(18) degrees , V=873.1(4) Angstrom(3) (data for 293 K structure). The structure consists of centrosymmetric dinuclear units in which each iron(II) atom is coordinated by two NCS(-) ions in the cis position and two nitrogen atoms of the bridging bpym ligand, with the remaining positions occupied by the peripheral bt ligand. The iron atom is in a severely distorted octahedral FeN(6) environment. The average Fe--N bond length of 2.15(9) Angstrom indicates that compound 1 is in the high-spin state (HS-HS) at 293 K. Crystal structure determinations at 240, 175 and 30 K gave a cell comparable to that seen at 293 K, but reduced in volume. At 30 K, the average Fe--N distance is 1.958(4) Angstrom, showing that the structure is clearly low spin (LS-LS). At 175 K the average Fe--N bond length of 2.052(11) Angstrom suggests that there is an intermediate phase. M?ssbauer investigations of the light-induced excited spin state trapping (LIESST) effect (lambda=514 nm, 25 mW cm(-2)) in 1 (4.2 K, H(ext)=50 kOe) show that the excited spin states correspond to the HS-HS and HS-LS pairs. The dynamics of the relaxation of the photoexcited states studied at 4.2 K and H(ext)=50 kOe demonstrate that HS-HS pairs revert with time to both HS-LS and LS-LS configurations. The HS-LS photoexcited pairs relax with time back to the ground LS-LS configuration. Complex [{Fe(0.15)Zn(0.85)(bt)(NCS)(2)}(2)bpym] (2) exhibits a continuous spin transition centred around 158 K in contrast to the two-step transition observed for 1. The different spin-crossover behaviour observed for 2 is due to the decrease of cooperativity (intermolecular interactions) imposed by the matrix of Zn(II) ions. This clearly demonstrates the role of the intermolecular interactions in the stabilization of the HS-LS intermediate state in 1. 相似文献
117.
Chebanov VA Muravyova EA Desenko SM Musatov VI Knyazeva IV Shishkina SV Shishkin OV Kappe CO 《Journal of combinatorial chemistry》2006,8(3):427-434
Multicomponent reactions (MCRs) and microwave-assisted organic synthesis (MAOS) have been used as key methods for the synthesis of fused dihydropyrimidine derivatives. The three-component condensation of 3-amino-5-alkylthio-1,2,4-triazoles with aromatic aldehydes and acetoacetamides under microwave irradiation was developed as a rapid and efficient solution-phase method for the high-yielding preparation of 7-aryl-2-alkylthio-4,7-dihydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxamide libraries. In addition, the selective reduction of the formed dihydrotriazolopyrimidines to trans-trans-2-alkylthio-7-aryl-4,5,6,7-tetrahydro-1,2,4-triazolo[1,5-a]pyrimidine-6-carboxamides was established. The described synthetic protocols provide rapid access to novel and diversely substituted dihydroazolopyrimidine libraries. 相似文献
118.
Larisa Kimovna Shubina Gunhild von Amsberg Vladimir Anatolievich Denisenko Roman Sergeevich Popov Sergey Anatolievich Dyshlovoy 《Natural product research》2019,33(10):1415-1422
A new pentacyclic guanidine alkaloid, monanchoxymycalin C (1) was isolated from a new collection of marine sponge Monanchora pulchra along with the known monanchoxymycalin A (2). The structure of 1 was elucidated on the basis of spectroscopic data. Monanchoxymycalin C exhibits cytotoxic activity against human cancer HeLa cells at low micromolar concentrations, induces apoptosis-related death of malignant cells and inhibits cancer cell colony formation. In addition, synergistic and additive effects have been observed in combination with cisplatin. 相似文献
119.
E. S. Tkachenko A. I. Druzhinina N. V. Avramenko R. M. Varushchenko A. L. Emelina I. A. Nesterov T. N. Nesterova 《Moscow University Chemistry Bulletin》2011,66(5):282-289
The heat capacity of 4,4′-dinitrodiphenyl ether and 4-nitro-4′-biphenylcarboxylic acid were measured by adiabatic calorimetry
(AC) in temperature ranges of 8–372 K and 10–372 K, respectively. The heat capacity of 4,4′-dinitrodiphenyl ether in the temperature
range 323–500 K, the thermodynamic properties of fusion, and the purity of the ether were measured by differential scanning
calorimetry (DSC). The main thermodynamic functions in the temperature range 5–370 K were calculated for both compounds using
the heat capacities of adiabatic calorimetry. Related thermodynamic functions of 4,4′-dinitrodiphenyl ether in the temperature
range 370–500 K were calculated on the basis of DSC data. 相似文献
120.
Intravital Imaging Study on Photodamage Produced by Femtosecond Near‐infrared Laser Pulses In Vivo 下载免费PDF全文
Sergey N. Arkhipov Ilyas Saytashev Marcos Dantus 《Photochemistry and photobiology》2016,92(2):308-313
Ultrashort femtosecond pulsed lasers may provide indispensable benefits for medical bioimaging and diagnosis, particularly for noninvasive biopsy. However, the ability of femtosecond laser irradiation to produce biodamage in the living body is still a concern. To solve this biosafety issue, results of theoretical estimations as well as the in vitro and in situ experiments on femtosecond biodamage should be verified by experimental studies conducted in vivo. Here, we analyzed photodamage produced by femtosecond (19, 42 and 100 fs) near‐infrared (NIR; ~800 nm) laser pulses with an average power of 5 and 15 mW in living undissected Drosophila larvae (in vivo). These experimental data on photodamage in vivo agree with the results of theoretical modeling of other groups. Femtosecond NIR laser pulses may affect the concentration of fluorescent biomolecules localized in mitochondria of the cells of living undissected Drosophila larva. Our findings confirm that the results of the mathematical models of femtosecond laser ionization process in living tissues may have a practical value for development of noninvasive biopsy based on the use of femtosecond pulses. 相似文献