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101.
Bhaskar Dhotare 《Tetrahedron letters》2005,46(17):3103-3105
(R)-2,3-Cyclohexylideneglyceraldehyde 1 has been used in a simple and efficient synthesis of (−)-muricatacin 10. The required chiron, syn-alkanetriol 2a was prepared by the reduction of a ketone 3 derived from 1. 相似文献
102.
The structure and conformational stability of ethyl pseudohalides CH3CH2 — XCN (X = O, S, Se) were investigated using ab initiocalculations at the MP2 level of theory with a triple- basis set augmented with polarization and diffusion functions. Full optimization was performed on the minimum energy structures as well as on the transition state forms. The relative stabilities of rotational conformers were calculated at the MP4 level using MP2 optimized reference geometries. The nature of all considered stationary points was verified by calculation of the harmonic vibrational frequencies. The calculated bond lengths, bond angles, dipole moments, and rotational constants of optimized global minima structures agree very well with the corresponding experimental data obtained from microwave spectroscopic studies. Also, available experimental frequencies are in good accord with the theoretical values. For ethyl cyanate CH3CH2 — OCN, the antiperiplanar (trans) form is predicted to be more stable than the synclinal (gauche) form, and the synperiplanar (cis) form corresponds to the transition state. For both ethyl thiocyanate CH3CH2 — SCN and ethyl selenocyanate CH3CH2 — SeCN, the gaucheform is the global minimum while the trans-conformer is a local minimum and the cis-form is a transition state. 相似文献
103.
Ab initio molecular orbital calculations employing a 4-31G basis set have been used to study the minimum energy paths for the formation of HCO+, COH+, and HCOH2+ from CO by protonation. The protonation of N2 to give NNH+ and HNNH2+ and of NO+ to form HNO2+ and NOH2+ have also been investigated. All species formed have linear equilibrium geometries and the minimum energy path for approach of the proton is along the line-of-centers of the heavy atoms. Energy barriers to the formation of the various species are given, where appropriate, and changes in geometry, ordering of molecular orbitals and orbital occupancy are discussed. 相似文献
104.
2-Trifluoromethyl-4H-thiochromene-4-thione obtained from 2-trifluoromethyl-4H-thiochromen-4-one and P2S5 reacts with aromatic amines, hydrazine hydrate, phenylhydrazine, and hydroxylamine at the C(4) atom of the chromene ring
to give the corresponding anils, azine, hydrazones, and oxime of thiochromone. 2-Trifluoromethyl-4H-thiochromen-4-one is oxidized by hydrogen peroxide in AcOH into 4-oxo-2-trifluoromethyl-4H-thiochromene 1,1-dioxide and reduced by NaBH4 to 2-trifluoromethyl-4H-thiochromen-4-ol or cis-2-(trifluoromethyl)thiochroman-4-ol. When treated with hydrazine hydrate, thiochromen-4-one gives 3(5)-(2-mercaptophenyl)-5(3)-trifluoromethylpyrazole.
Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 504–509, March, 2006. 相似文献
105.
A New Tricyclic Sulfur-rich Phosphane From the products of the reaction of P4S3 with tert-Butyliodide the compound (t-Bu(S)P)2P4S3 was isolated in low yield. The compound is stable and has a structure related to the hydrocarbon brexane. By reaction with triphenylphosphin the compounds (t-BuP)(t-Bu(S)P)P4S3 and (t-BuP)2P4S3 were obtained. The 31P-nmr spectra of all compounds were solved and used to determine the structure of the molecules. A complete set of 31P-nmr data is given. 相似文献
106.
Yi Gao Xuesong Yao Qinggeng Jiang Jianhe Liao Yongping Chen Rentong Yu 《Molecules (Basel, Switzerland)》2022,27(10)
Microgels have unique and versatile properties allowing their use in forward osmosis areas as a draw agent. In this contribution, poly(4-vinylpyridine) (P4VP) was synthesized via RAFT polymerization and then grafted to a poly(N-Isopropylacrylamide) (PNIPAAm) crosslinking network by reverse suspension polymerization. P4VP was successfully obtained by the quasiliving polymerization with the result of nuclear magnetic resonance and gel permeation chromatography characterization. The particle size and particle size distribution of the PNIPAAm-g-P4VP microgels containing 0, 5, 10, 15 and 20 wt% P4VP were measured by means of a laser particle size analyzer. It was found that all the microgels were of micrometer scale and the particle size was increased with the P4VP load. Inter/intra-molecular-specific interactions, i.e., hydrogen bond interactions were then investigated by Fourier infrared spectroscopy. In addition, the water flux measurements showed that all the PNIPAAm-g-P4VP microgels can draw water more effectively than a blank PNIPAAm microgel. For the copolymer microgel incorporating 20 wt% P4VP, the water flux was measured to be 7.48 L∙m−2∙h−1. 相似文献
107.
108.
Tarita Biver 《Molecules (Basel, Switzerland)》2022,27(13)
G-quadruplexes (G4) are now extensively recognised as a peculiar non-canonical DNA geometry that plays a prime importance role in processes of biological relevance whose number is increasing continuously. The same is true for the less-studied RNA G4 counterpart. G4s are stable structures; however, their geometrical parameters may be finely tuned not only by the presence of particular sequences of nucleotides but also by the salt content of the medium or by a small molecule that may act as a peculiar topology inducer. As far as the interest in G4s increases and our knowledge of these species deepens, researchers do not only verify the G4s binding by small molecules and the subsequent G4 stabilisation. The most innovative studies now aim to elucidate the mechanistic details of the interaction and the ability of a target species (drug) to bind only to a peculiar G4 geometry. In this focused review, we survey the advances in the studies of the binding of small molecules of medical interest to G4s, with particular attention to the ability of these species to bind differently (intercalation, lateral binding or sitting atop) to different G4 topologies (parallel, anti-parallel or hybrid structures). Some species, given the very high affinity with some peculiar G4 topology, can first bind to a less favourable geometry and then induce its conversion. This aspect is also considered. 相似文献
109.
X射线增感屏用纳米CaWO4的Pechini溶胶-凝胶法制备及其光学性能 总被引:1,自引:0,他引:1
采用Pechini溶胶-凝胶法制得纳米级CaWO4荧光粉,通过X射线衍射图、扫描电镜和发射光谱对其形貌和发光性能进行了研究,结果表明750℃条件下所得样品为纯相CaWO4晶体,在X射线激发下发射峰位于420nm,与感蓝胶片的光谱灵敏度匹配良好。其粒径在纳米量级且粒度分布集中是该方法所得CaWO4荧光粉的突出优点。将此荧光粉制成X射线增感屏并与市售同类产品相比,该增感屏可使感光片的成像质量显著提高。 相似文献
110.