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1.
2.
Purushotham Reddy Karra 《合成通讯》2013,43(18):2333-2338
A short total synthesis of a diacetoxylated E,E-diene lactone ent-hyptenolide, was achieved involving from Phosphonate and cis-butene 1,4-diol. Brown Asymmetric allylation, Acrylation, Acetylation, Ring-closing metathesis as the key steps has been described. Moreover, the biological activity of ent-hyptenolide was evaluated on HeLa, A549, IMR32, and MDA-MB231 cancer cell lines. The ent-hyptenolide selectively and potently inhibited the growth of IMR32 cell line. 相似文献
3.
《Chemical physics letters》1985,119(1):38-41
We present photoelectron spectra of the lowest singlet state (1E′') of sym-triazine obtained with 2 ns and 5 ps excitation sources. Comparisons of picosecond and nanosecond spectra are made at three wavelengths, corresponding to the 601, 602 and the 6011201 vibrational levels. The spectra show that rapid (</ 5 ps) relaxation to the lowest triplet state occurs subsequent to singlet excitation. Coupling of S1 levels to the T1 manifold is very inhomogeneous with intersystem crossing rates ranging from 107 s−1 to > 1011 s−1. Furthermore, for excitation at the 6011201 level we find evidence for relaxation to another excited state at rates ⩾ 1011 s−1. 相似文献
4.
A trisubstituted cyclopentane chiron has been prepared by dynamic kinetic reduction of a pulegone-derived β-keto ester. This chiron served as the starting material for the synthesis of the reported structure of the tricyclic sesquiterpene trans-africanan-1α-ol. The synthetic material was not congruent with the natural product. 相似文献
5.
《Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy》1984,40(7):687-689
The Fermi coupling coefficient W, which measures the intensity of the resonance interaction and is proportional to the anharmonic force constant Ksδδ of the amino group, is measured by two independent methods in 1:1 complexes of trifluoroethylamine with bases in dilute CCl4 solutions.Values of W from the intensity ratio of Fermi doublet components R, are in good agreement with more precise calculation based on frequencies νs, νa and 2δ of the protio species (NH2) and νfνb of the monodeutero species (NHD). There is a large sensitivity of W to the pKB of the base but there is no appreciable temperature dependence. 相似文献
6.
Abstract There are more than eighty serotypes of Vibrio cholerae, all causing disease with symptoms of Asian cholera. Systematic prevention of cholera by immunization has not yet been achieved because of a lack of a protective vaccine. Vibrio cholerae 0:1 Gramnegative bacteria occur as two immunologically distinct strains: Ogawa and Tnaba. The lipopolysaccharide (LPS) of both strains seem to contain the same 0-polysaccharide antigen consisting3,4 of (1+2)-a-linked 4-amino-4,6-dideoxy-a-D-mannopyranosyl residues the amino groups of which are acylated with 3-deoxy-L-glycero-tetronic acid. Although the chemical structure of the 0-polysaccharides has been known5 since 1979, the synthesis of its monomeric repeating unit was reported only in 1988. 相似文献
7.
By using three different hybrid exchange-correlation functionals containing 20%, 35%, and 50% of exact Hartree-Fock (HF) exchange of the density functional theory and its time-dependent extension plus the Hartree-Fock and the configuration interaction of single excitation methods, equilibrium geometries, and their 30 vibrational-normal-mode frequencies of the ground S(0)((1)A(1)) and the first excited S(1)((1)B(2)) states of fluorobenzene (FB) were calculated. The dispersed fluorescence spectrum and internal conversion (IC) rate of the A(1)B(2)→X(1)A(1) transition were simulated by Franck-Condon (FC) calculations within the displaced harmonic oscillator approximation plus anharmonic and distorted corrections. The simulated spectral profile is primarily described by the Franck-Condon progression from the ring-breathing modes ν(9) and ν(10) which belong to totally symmetry modes. Anharmonic corrections simultaneously improve the intensity order of 9(1)(0) and 10(1)(0) bands and diminish 1(1)(0) transition that is fairly strong in harmonic simulations. It is concluded that the amount of Hartree-Fock exchange does impact the geometries and vibrational frequencies of FB molecule, but not the relative intensities of the transitions. It is anharmonic corrections that make the relative intensities of the transitions in good agreement with experimental results. Distorted corrections could assign most of the dominant overtones of out-of-plane nontotally symmetry modes, and the results agree well with the experimental assignments. Furthermore, it was found that the internal conversion rate is dominated by three promoting modes that are computed with lowing symmetry to C(1). By choosing dephasing width as 10 cm(-1) that is consistent with spectral simulation, we obtained the lifetimes of the A(1)B(2)→X(1)A(1) de-excitation as 11 and 19 ns, respectively, from TD(B3LYP) and HF∕CIS calculations in comparison with the experimental value 14.75 ns. 相似文献
8.
LI Wan-nan ZHUANG Yan LI He SUN Ying FU Yao WU Xiao-xia ZHAO Zhi-zhuang FU Xue-qi 《高等学校化学研究》2008,24(5)
This study is focused on the expression of an SH2 domain-truncated form of protein tyrosine phosphatase SHP-1(designated △SHP-1) and the preparation of its polyelonal antibodies.A cDNA fragment encoding △SHP-1 was amplified by PCR and then cloned into the pT7 expression vector.The recombinant pT7-△SHP-1 plasmid was used to transform Rosetta(DE3) E.coll cells.△SHP-1 was distributed in the exclusion body of E.coll cell extracts and was purified through a two-column chromatographic procedure.The purified enzyme exhibited an expected molecular weight on SDS-gels and HPLC gel filtration columns.It possesses robust tyrosine phosphatase activity and shows typical enzymatic characteristics of classic tyrosine phosphatases.To generate polyclonal anti-△SHP-1 antibodies,purified recombinant △SHP-1 was used to immunize a rabbit.The resultant anti-serum was subjected to purification on △SHP-1 antigen affinity chromatography.The purified polyclonal antibody displayed a high sensitivity and specificity toward △SHP-1.This study thus provides the essential materials for further investigating the biological function and pathological implication of SHP-1 and screening the inhibitors and activators of the enzyme for therapeutic drug development. 相似文献
9.
LIU Chuan-Pu ZOU Sheng-Li GUO Jing-Zhong GU Yue-ShuDepartment of Chemistry Shandong University Jinan Shandong ChinaCHU Yan-Nan CAO De-ZhaoLaser Spectroscopy Laboratory Anhui Institute of Optics Fine Mechanics Chinese Academy of Sciences Hefei Anhui China 《中国化学》1997,15(3):211-217
Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v"=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed. 相似文献
10.
LI Wan-nan ZHUANG Yan LI He SUN Ying FU Yao WU Xiao-xia ZHAO Zhi-zhuang FU Xue-qi . Edmond H. Fischer Signal Transduction Laboratory College of Life Sciences . Key Laboratory for Molecular Enzymology & Engineering Ministry of Education Jilin University Changchun P. R. China 《高等学校化学研究》2008,24(5):592-596
This study is focused on the expression of an SH2 domain-truncated form of protein tyrosine phosphatase SHP-1(designated ΔSHP-1) and the preparation of its polyclonal antibodies. A cDNA fragment encoding ΔSHP-1 was amplified by PCR and then cloned into the pT7 expression vector. The recombinant pT7-ΔSHP-1 plasmid was used to transform Rosetta(DE3) E. coli cells. ΔSHP-1 was distributed in the exclusion body of E. coli cell extracts and was purified through a two-column chromatographic procedure. The purified enzyme exhibited an expected molecular weight on SDS-gels and HPLC gel filtration columns. It possesses robust tyrosine phosphatase activity and shows typical enzymatic characteristics of classic tyrosine phosphatases. To generate polyclonal anti-ΔSHP-1 antibodies, purified recombinant ΔSHP-1 was used to immunize a rabbit. The resultant anti-serum was subjected to purification on ΔSHP-1 antigen affinity chromatography. The purified polyclonal antibody displayed a high sensitivity and specificity toward ΔSHP-1. This study thus provides the essential materials for further investigating the biological function and pathological implication of SHP-1 and screening the inhibitors and activators of the enzyme for therapeutic drug development. 相似文献
11.
Mercaptans in petroleum products wreck the quality of finished products, so it is necessary to remove them in petroleum refining industry. Merox fixed-bed process is widely used in which mercaptans are converted by contacting feedstock with a metal phthalocyanine catalyst in the presence of air and an alkaline agent. However, use of caustic brings a spent caustic disposal problem so that novel caustic-free catalysts are highly desired to meet environment requirements1-3. It is not just simply … 相似文献
12.
In this paper we show that a pseudo-Jahn-Teller (PJT) coupling between the (1)A1g ground state and the (1)B2u excited states along the Kekulé mode of b2u symmetry is responsible for the surprisingly low frequency of this mode in the ground state and its remarkable upward shift of 261 cm(-1) upon excitation to the first (1)B2u excited state. 相似文献
13.
Verbitskiy E. V. Slepukhin P. A. Ezhikova M. A. Kodess M. I. Shvachko Yu. N. Starichenko D. V. Rusinov G. L. Charushin V. N. 《Russian Chemical Bulletin》2011,60(5):975-980
O- and C-Adducts of 5-(het)aryl-2,3-dicyano-1-ethylpyrazinium salts are latent sources of biradicals capable of forming tetraazaphenanthrene
derivatives via dimerization. The mechanisms of the reactions were examined using ESR spectroscopy. The stereochemistry of the resulting
heterocyclic systems was studied by NMR spectroscopy. The crystallographic data on their three-dimensional structures were
obtained. 相似文献
14.
The kinetics of the induction period in the polymerization of 1-octene catalyzed by Solvay TiCl3-alkyl aluminium was studied with a dilatometer. The induction period decreases as [TiCl3] and [M]0 increase and temperature rises. It was observed through a microscope that large catalyst particles broke up into small particles in the induction period. So a kinetic model was proposed which ascribes the induction period to the breaking up of catalyst particles under the effect of polymer, and the most of the experimental results can be explained on the basis of the model. 相似文献
15.
《Chemical physics letters》1987,138(5):419-424
The relaxation rate constants of the low-lying electronic singlet states, a 1Δg and b 1Σ+g , of gaseous natural O2 and of the isotope 18O2 were investigated as a function of temperature from 100 to 295 K. The measured increase of the rate constants with temperature is in good agreement with a theory of electronic-to-vibrational-translational energy transfer. The significant effects of the different electronic states and of the isotope masses on the absolute values of the relaxation rate constants, which range from 1.0× 10−20 to 3.9× 10−17 s−1 molecule−1 cm3 at 295 K, are discussed. 相似文献
16.
F. El-Kabbany F. M. Mansey H. Naguib A. Al-Huwari 《Journal of Thermal Analysis and Calorimetry》1997,48(2):287-295
The effect of partial replacement of K+ by Ag+ in the mixed system of KNO3 and AgNO3 during a set of DSC heating cycles was studied by means of a modern computerized DSC system. Thermal analysis was performed in the vicinity of the phase transition II I for pure KNO3. The results revealed a large change in enthalpy and the phase transition temperature close to the morphotropic boundary x=0.5–0.6. At this boundary, the transformation enthalpy reached the maximum value of 101 J g–1. On the basis of the data obtained from this accurate thermal analysis work, a model is suggested for the energy barrier of rotation of the nitrate ion in the mixed nitrate system. 相似文献
17.
A. L. M. de Oliveira M. R. S. Silva H. Sales E. Longo A. S. Maia A. G. Souza I. M. G. Santos 《Journal of Thermal Analysis and Calorimetry》2013,114(2):565-572
Strontium stannate titanate Sr(Sn, Ti)O3 is a solid solution between strontium stannate (SrSnO3) and strontium titanate (SrTiO3). In the present study, it was synthesized at low temperature by the polymeric precursor method, derived from the Pechini process. The powders were calcined in oxygen atmosphere in order to eliminate organic matter and to decrease the amount of SrCO3 formed during the synthesis. The powders were annealed at different temperatures to crystallize the samples into perovskites-type structures. All the compositions were studied by thermogravimetry (TG) and differential thermal analysis (DTA), infrared spectroscopy (IR) and X-ray diffraction (XRD). The lattice former, Ti4+ and Sn4+, had a meaningful influence in the mass loss, without changing the profile of the TG curves. On the other hand, DTA curves were strongly modified with the Ti4+:Sn4+ proportion in the system indicating that intermediate compounds may be formed during the synthesis being eliminated at different temperature ranges, while SrCO3 elimination occurs at higher temperature as shown by XRD and IR spectra. 相似文献
18.
Abstract The two strategies engaged in the construction of the title disaccharide 17 comprise: 1. assembly of a diamino disaccharide and its N-acylation using chiral reagents to introduce the 4-(3-deoxy-l-glycero-tetronyl) group, followed by deprotection, and 2. preparation of a glycosyl acceptor and a glycosyl donor both having the chiral 3-deoxy-l-glycero-tetronamido group already in place, their condensation to give a fully substituted disaccharide, and deprotection. Accordingly, the crystalline diamino disaccharide methyl 2-O-(4-amino-3-O-benzyl-4, 6-dideoxy-α-d-mannopyranosyl)-4-amino-3-O-benzyl-4, 6-dideoxy-α-d-mannopyranoside, (14), was prepared from the known [Bundle, D. R. et al., Carbohydr. Res. 174, 239 (1988)] diazido disaccharide 12, and treated with the lactone 30, or its acetylated or benzylated analogs 31 and 32, respectively, as the N-acylating reagents. Subsequent deprotection of the respective products applying standard chemistry gave 17. Alternatively, the methyl α-glycoside of the monomeric intracatenary repeating unit of Vibrio cholerae 0:1 (2) was converted to the fully benzoylated glycosyl chloride 26, and the latter glycosyl donor was condensed with methyl 3-O-benzyl-4,6-dideoxy-4-(2,4-di-O-benzoyl-3-deoxy- l-glycero-tetronamido)-α-d-mannopyranoside (24), to give the corresponding, fully protected derivative 27. Deprotection then readily gave 17. It appears that the title disaccharide can be most efficiently synthesized using synthons 24 and 26. The lactones 30 and 32 appear to be promising acylating reagents for the introduction of the 3-deoxy-l-glycero-tetronamido group when higher oligosaccharides in this series will be synthesized via their (poly)amino precursors. 相似文献
19.
Xing Zhou LI Ke Mei WU Dao Fei HUANG Liang HUANG* Institute of Materia Medica Chinese Academy of Medical Sciences & Peking Union Medical College. Xian Nong Tan St. Beijing 《中国化学快报》2002,13(6):528-530
(-) Clausenamide (1) showed strong nootropic action, while its (+) antipode had no such an action. The content of CM1(2) in the metabolites of (-)1 is much higher than that of (+)11. For comparing the nootropic activity of enantiomers, (+) and (-) CM1 were synthesized. CM1 is the hydroxylated product of the N-methyl group of clausenamide. Oxidation of the C3-OH and C6-OH protected clausenamide to introduce the hydroxyl group into the methyl was tried but unsuccessful. Then de novo s… 相似文献
20.
《Tetrahedron》2019,75(33):4570-4576
Synthesis of the C1–C13 fragment of eribulin mesylate has been accomplished. It features a highly stereoselective construction of a trans-dihydropyran framework using three key reactions: (1) Sharpless epoxidation, (2) regioselective ring opening, and (3) olefin metathesis. 相似文献