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《Inorganica chimica acta》1989,156(2):251-256
The title compounds (1, X=F; 2, X=Cl) were obtained in quantitative yield by refluxing together (NBu4)2[Pd2(μ-Br)2(C6X5)4] and (NBu4)2[Pd2(μ-Br)2Br4]. Treatment of 1 or 2 with AgClO4 (Pd:Ag= 1:1) gave solutions which behaved as containing ‘Pd(C6X5)Br’. 1, 2 and the ‘Pd(C6X5)Br’ solutions were checked as precursors of mono-pentahalophenyl derivatives, yielding a variety of complexes [Pd(C6X5)Br(L-L)] (L-L=bipy, tmen, dpe, COD), [Pd(C6X5)BrL2] (L=p-TolNH2, py, PPh3, AsPh3, SbPh3), [Pd2(μ-Br)2(C6X5)2L2] (X=F, L=AsPh3; X=Cl, L=SbPh3) and (NBu4)[Pd(C6X5)Br2L] (X=F, L= py, AsPh3, SbPh3; X=Cl, L=p-TolNH2, py, PPh3, AsPh3, SbPh3). The solutions of ‘Pd(C6X5)Br’ proved to be the best general precursors of complexes [Pd(C6X5)BrL2] although complexes with OPPh3 could not be obtained.  相似文献   

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The quadrupole split asymmetric 125Te Mössbauer spectrum recorded from the compound (Te2)2(I2), in which monomolecular planar layers of iodine molecules are intercalated between layers of tellurium, is a reflection of the distorted environment of tellurium atoms in a two-dimensional layered compound in which the elongated flat crystals are preferentially orientated. The differences between the Mössbauer parameters recorded from (Te2)2(I2) and those recorded from elemental tellurium and the tellurium(0) species in the compound Te3Cl2 are associated with small differences between the environments of tellurium in the three compounds. The Mössbauer spectra recorded from (Te2)2(I2) are consistent with a recently proposed model on which the electronic band structure of (Te2)2(I2) has been derived.  相似文献   

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The association of Os(bpy)32+ and stellacyanin was investigated by measuring the emission polarization of the excited state of the complex [*Os-(bpy)32+]. At high protein concentration (≥1 mM) Os(bpy)32+ appears to bind weakly to reduced stellacyanin and to oxidized stellacyanin to a lesser extent. These results are consistent with those obtained in a previous kinetic study on the redox quenching of *Ru(bpy)32+ by stellacyanin [1]. On excitation at 480 nm, the limiting polarization (Po) of the *Os(bpy)32+ emission at 715 nm is 0.100. From Po we concluded that (1) protein-bound Os(bpy)32+ has considerable rotational freedom independent of the protein-probe complex, and (2) the emission dipole of *Os(bpy)32+ is at ∼45° to the C3 molecular axis.  相似文献   

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Human β-defensin 2 (HBD2) is a member of the defensin family of antimicrobial peptides that plays important roles in the innate and adaptive immune system of both vertebrates and invertebrates. In addition to their direct bactericidal action, defensins are also involved in chemotaxis and Toll-like receptor activation. In analogy to chemokine/glycosaminoglycan (GAG) interactions, GAG-defensin complexes are likely to play an important role in chemotaxis and in presenting defensins to their receptors. Using a gel mobility shift assay, we found that HBD2 bound to a range of GAGs including heparin/heparan sulfate (HS), dermatan sulfate (DS), and chondroitin sulfate. We used NMR spectroscopy of (15)N-labeled HBD2 to map the binding sites for two GAG model compounds, a heparin/HS pentasaccharide (fondaparinux sodium; FX) and enzymatically prepared DS hexasaccharide (DSdp6). We identified a number of basic amino acids that form a common ligand binding site, which indicated that these interactions are predominantly electrostatic. The dissociation constant of the [DSdp6-HBD2] complex was determined by NMR spectroscopy to be 5 ± 5 μM. Binding of FX could not be quantified because of slow exchange on the NMR chemical shift time scale. FX was found to induce HBD2 dimerization as evidenced by the analysis of diffusion coefficients, (15)N relaxation, and nESI-MS measurements. The formation of FX-bridged HBD2 dimers exhibited features of a cooperative binding mechanism. In contrast, the complex with DSdp6 was found to be mostly monomeric.  相似文献   

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For use as the internal standards in a quantitative analysis of natural jasmonic acid (JA) and methyl jasmonate (JAMe) by gas chromatography-mass spectrometry-selected ion monitoring, (±)-2-(2,3–2H2)JA and its methyl ester, (±)-2-(2,3–2H2)JAMe, were efficiently prepared from 2-(2–pentyl)-2-cyclopentenone through catalytic semi-deuteriogenation of acetylenic intermediates with deuterium gas in pyridine.  相似文献   

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Interesting and very promising antisense properties of 2′-deoxy-2′-fluoroarabinonucleic acids ((a) Wilds, C.J.; Damha, M.J. 2′-Deoxy-2′-fluoroarabinonucleosides and oligonucleotides (2′F-ANA): synthesis and physicochemical studies. Nucl. Acids Res. 2000, 28, 3625–3635; (b) Viazovkina, E.; Mangos, M.; Elzagheid, M.I.; Damha, M.J. Current Protocols in Nucleic Acid Chemistry 2002, 4.15.1–4.15.21) (2′F-ANA) has encouraged our research group to optimize the synthetic procedures for 2′-deoxy-2′-fluoro-β-D-arabinonucleosides (araF-N). The synthesis of araF-U, araF-T, araF-A and araF-C is straightforward, (Tann, C.H.; Brodfuehrer, P.R.; Brundidge, S.P.; Sapino, C., Jr. Howell H.G. Fluorocarbohydrates in synthesis. An efficient synthesis of 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-5-iodouracil (β-FIAU) and 1-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)thymine (β-FMAU). J. Org. Chem. 1985, 50, 3644–3647; Howell, H.G.; Brodfuehrer, P.R.; Brundidge, S.P.; Benigni, D.A.; Sapino, C., Jr. Antiviral nucleosides. A stereospecific, total synthesis of 2′-fluoro-2′-deoxy-β-D-arabinofuranosyl nucleosides. J. Org. Chem. 1988, 53, 85–88; Maruyama, T.; Takamatsu, S.; Kozai, S.; Satoh, Y.; Izana, K. Synthesis of 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)adenine bearing a selectively removable protecting group. Chem. Pharm. Bull. 1999, 47, 966–970) however, the synthesis of the guanine analogue is more complicated and affords poor to moderate yields of araF-G (4) ((a) Elzagheid, M.I.; Viazovkina, E.; Masad, M.J. Synthesis of protected 2′-deoxy-2′-fluoro-β-D-arabinonucleosides. Synthesis of 2′-fluoroarabino nucleoside phosphoramidites and their use in the synthesis of 2′F-ANA. Current Protocols in Nucleic Acid Chemistry 2002, 1.7.1–1.7.19; (b) Tennila, T.; Azhayeva, E.; Vepsalainen, J.; Laatikainen, R.; Azhayev, A.; Mikhailopulo, I. Oligonucleotides containing 9-(2-deoxy-2-fluoro-β-D-arabinofuranosyl)-adenine and -guanine: synthesis, hybridization and antisense properties. Nucleosides, Nucleotides and Nucl. Acids 2000, 19, 1861–1884). Here we describe an efficient synthesis of araF-G (4) that involves coupling of 2-deoxy-2-fluoro-3,5-di-O-benzoyl-α-D- arabinofuranosyl bromide (1) with 2-chlorohypoxanthine (2) to afford 2-chloro-β-araF-I (3) in 52% yield. Nucleoside (3) was transformed into araF-G (4) by treatment with methanolic ammonia (150°C, 6 h) in 67% yield.  相似文献   

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The structures of three Pt(II) thiourea complexes, trans-[(tu)2Pt(NH3)2]Cl2 (1), trans-[(tu)2Pt(CH3NH2)2]Cl2·3H2O (2) and [Pt(tu)4]Cl2 (3), have been determined by X-ray diffraction and refined to R = 0.049 for 1026 reflections (1), R = 0.057 for 2547 reflections (2) and R = 0.046 for 2792 reflections (3). All the compounds crystallize in the space group P21/c and have cell dimensions: a = 5.437(1), b = 6.450(1), c = 17.980(3) Å, β = 96.05(2)°, Z = 2 (compound 1); a = 9.225(1), b = 15.404(2), c = 12.601(2) Å, β = 105.39(2)°, Z = 4 (compound 2); and a = 9.051(6), b = 10.203(6), c = 18.263(8) Å, β = 91.12(8)°, Z = 4 (compound 3). The unit cell of 1 and 3 contains only a single type of cation, while that of 2 is formed from two independent cations. In 1 and 2 the coordination spheres of the Pt atoms are rather similar, with angles close to 90° and coplanarity of the metal and respective donor atoms. Instead, in 3 the four sulfur atoms, which surround the Pt, display a slight distortion (0.06 Å from the mean plane) towards tetrahedral.  相似文献   

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A new high yielding synthesis of the seven-coordinate complexes [MI2(CO)3{Ph2P(CH2)nPPh2}] (M = Mo and W; n = 1–6) is described. The procedure involves reacting the complexes [MI2(CO)3(NCMe)2] in CH2Cl2 with an equimolar amount of the bidentate phosphorus ligand. The low temperature (−70 °C) 13C NMR spectra of the complexes [Wl2(CO)3{Ph2P(CH2)nPPh2}] (n = 3 and 5) indicates that the geometry is capped octahedral with a carbonyl ligand in the unique capping position.  相似文献   

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The resonance Raman spectra of K2(Ti(O2)(SO4)2)·5H2O and K2(Ti(O2)(C2O4)2)·3H2O are recorded. The results are consistent with the triangular structure of the peroxotitanium unit, Ti(O2), with C symmetry. The ν(OO), νs(TiO) and νas(TiO) are observed around 890, 610 and 535 cm−1, respectively. The resonance effects are shown to be associated with the 425 nm absorption band. This band is assigned to the O22− → Ti(IV) charge-transfer transition. The calculated force constant values for the O22− and TiO bonds are 320 and 275 N m−1, respectively.  相似文献   

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Abstract

2′-C-Cyanomethyl-2′-deoxy-arabinosylcytosine 3 and 2′-C-azidomethyl-2′-deoxy-arabinosylcytosine 4 were synthesized from uridine. The antineoplastic activities of these compounds were evaluated.  相似文献   

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The 2′-deoxy and ara derivatives of 1-β-(D-ribofuranosyl)-1,2-dihydropyrimidin-2-one (zebularine) were synthesized by improved routes and tested for their inhibitory properties against cytidine deaminase. It was shown that the Ki′s of both compounds were comparable to that of the parent zebularine in inhibition studies with purified enzyme. In contrast to zebularine, 2′-deoxy and ara zebularine showed only nominal cytotoxicity against MOLT-4 and L1210 cells in vitro. A model compound for the inhibition of deoxycytidylate deaminase, 2′-deoxyzebularine 5′-monophosphate (6), was also prepared.  相似文献   

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