DNA binding and photocleavage properties of two mixed-ligand oxovanadium complexes

An oxovanadium complex [VO(satsc)(bipy)] (1) (satsc = salicylaldehyde thiosemicarbazone, bipy = 2,2′-bipyridine) and its dibromo derivative [VO(3,5-dibrsatsc)(bipy)] (2) (3,5-dibrsatsc = 3,5-dibromosalicylaldehyde thiosemicarbazone) have been synthesized and characterized by elemental analysis, IR, ES-MS and ¹H NMR. The interaction of these two complexes with calf-thymus DNA (CT-DNA) was studied using UV/Vis, fluorescence spectroscopic titration, viscosity measurements and thermal denaturation. The results suggest that complexes 1 and 2 interact with CT-DNA by intercalative modes. The DNA-binding affinity of complex 1 is larger than that of complex 2. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated by gel electrophoresis experiments. Both complexes exhibit significant DNA cleavage activity, and complex 1 showed greater cleaving efficiency than complex 2.     

Langmuir-Blodgett film of p-tert-butylthiacalix[4]arene modified glassy carbon electrode as voltammetric sensor for the determination of Hg(II)

The π-A isotherms and UV-vis spectra of the transferred films suggested that the monolayer of p-tert-butylthiacalix[4]arene can coordinate with Hg²⁺ at the air-water surface. From these observations, a glassy carbon electrode coated with Langmuir-Blodgett film of p-tert-butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg²⁺. Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir-Blodgett film-modified electrode can greatly improve the measuring sensitivity of Hg²⁺. Under the selected conditions, the Langmuir-Blodgett film-modified electrode in 0.1 mol L⁻¹ H₂SO₄ + 0.01 mol L⁻¹ KCl solution shows a linear voltammetric response for Hg²⁺ in the range of 5.0 × 10⁻¹⁰ to 1.5 × 10⁻⁷ mol L⁻¹, with a detection limit of 2.0 × 10⁻¹⁰ mol L⁻¹. The proposed method was also applied to determine Hg²⁺ in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability.     

A New Cardenolide and Two New Pregnane Glycosides from the Root Barks of Periploca sepium

A new cardenolide and two new pregnane glycosides, periplogenin 3‐[O‐β‐glucopyranosyl‐(1→4)‐β‐sarmentopyranoside] ( 1 ), (3β,20S)‐pregn‐5‐ene‐3,17,20‐triol 20‐[O‐β‐glucopyranosyl‐(1→6)‐O‐glucopyranosyl‐(1→4)‐β‐canaropyranoside] ( 2 ), and (3β,14β,17α)‐3,14,17‐trihydroxy‐21‐methoxypregn‐5‐en‐20‐one 3‐[O‐β‐oleandropyranosyl‐(1→4)‐O‐β‐cymaropyranosyl‐(1→4)‐β‐cymaropyranoside] ( 3 ), were isolated from the root barks of Periploca sepium Bge , together with seven related known compounds, periplogenin, xysmalogenin, (3β,20S)‐pregn‐5‐ene‐3,17,20‐triol, (3β,14β,17α)‐3,14,17‐trihydroxy‐21‐methoxypregn‐5‐en‐20‐one, (3β,20S)‐pregn‐5‐ene‐3,20‐diol 3‐β‐glucopyranoside 20‐β‐glucopyranoside, (3β,20S)‐pregn‐5‐ene‐3,20‐diol 3‐[O‐2‐O‐acetyl‐β‐digitalopyranosyl‐(1→4)‐β‐cymaropyranoside] 20‐[O‐β‐glucopyranosyl‐(1→6)‐O‐β‐glucopyranosyl‐(1→2)‐β‐digitalopyranoside], and (3β,20S)‐ pregn‐5‐ene‐3,20‐diol 20‐[O‐β‐glucopyranosyl‐(1→6)‐β‐glucopyranoside]. Their structures were elucidated on the basis of spectroscopic analyses.     

Three New Caged Prenylxanthones from Garcinia bracteata

Three new caged prenylxanthones (xanthone=9H‐xanthen‐9‐one), named neobractatin ( 1 ), 3‐O‐methylneobractatin ( 2 ), and 3‐O‐methylbractatin ( 3 ), along with eight known compounds, were isolated from the twig of Garcinia bracteata. The structures of the new compounds were elucidated on the basis of 1D‐ and 2D‐NMR experiments, including HMBC, HSQC, ¹H,¹H‐COSY, and ROESY, as well as HR‐MS analysis.     

Superacid mediated reactions applied to 4-aminobenzofused sultams and fluorinated 4-aminobenzene sulfonamides synthesis

A novel series of 4-aminobenzofused sultams was prepared using an efficient synthetic procedure based on superacid mediated reactions followed either by copper-catalyzed coupling or S_NAr reactions. The synthetic potential of the method toward the divergent synthesis of novel potent bioactive (fluorinated) aminobenzofused sultams and fluorinated 4-aminobenzene sulfonamides was shown, making it a new valuable process to synthesize a large diversity of compounds in bioactive 4-aminobenzene sulfonamide family.     

Dimerization of 2-pyridylisonitriles produces π-extended fused heteroarenes useful as highly selective colorimetric and optical probes for copper ion

A very simple synthesis of pyrido[2″,1″:2′,3′]imidazo[4′,5′:4,5]imidazo[1,2-a]pyridines 2 was achieved from the dimerization of 2-pyridylisonitriles. The optical responses of these π-extended fused heteroarenes to a series of metal ions were investigated by means of UV-visible absorption spectrum in acetonitrile. It was found that most of compounds 2 selectively responded to Cu²⁺, and the limit of detection was about 3.5×10⁻⁷ M when using the best probe, 3,9-dimethylpyrido[2″,1″:2′,3′]imidazo[4′,5′:4,5]imidazo[1,2-a]pyridine 2d. Meanwhile some compounds 2 specifically showed a color change from colorless to red or yellow when they are exposed to copper ion in acetonitrile, whereas other transitional, alkali and alkaline earth metal ions could not induce a color change. This work not only established a direct access to π-extended fused heteroarenes, but also supplied novel sensitive and selective colorimetric and optical probes for copper ion.     

TTFAQ-cored D/A ensembles: synthesis, electronic properties, and redox responses to transition metal ions

Two anthraquinone-type π-extended tetrathiafulvalene (TTFAQ)-cored D/A triads were synthesized and characterized by UV-vis absorption and cyclic voltammetric analyses. Electronic substituent effects were unraveled by making a comparison with analogous TTFAQ derivatives previously reported. Electrochemical titrations of the two TTFAQ D/A triads with selected transition metal cations (Ag⁺ and Cu²⁺) were examined by cyclic voltammetry, and the results suggest potential application of such TTFAQ derivatives as electrochemical sensors for transition metal ions.     

纤维素-[Amim]Cl浓溶液的稳态流变规律

对纤维素-氯代1-烯丙基-3-甲基咪唑([Amim]Cl)浓溶液在不同温度下的稳态流变规律进行了研究。测试结果显示:纤维素-[Amim]Cl浓溶液属于假塑性流体。运用Cross和Carreau两种黏度模型对实验数据进行拟合,得到了表观黏度的主曲线,通过Arrhenius方程确定了移位活化能(ΔEa)为91.86~164.97 kJ/mol。与纤维素-氯代1-丁基-3-甲基咪唑([Bmim]Cl)溶液、纤维素-N-甲基吗啉-N-氧化物(NMMO)溶液、熔融聚合物(如聚丙烯、聚乙烯等)的活化能以及流变规律进行了对比。结果表明,纤维素-[Amim]Cl浓溶液的ΔEa较高,温度对体系黏度影响较大。     

New Guaipyridine Sesquiterpene Alkaloids from Artemisia rupestris L.

Three new guaipyridine sesquiterpene alkaloids, rupestine A, B, C ( 1 – 3 , resp.), and the new nor‐sesquiterpne alkaloid rupestine D ( 4 ) were obtained from the flowers of Artemisia rupestris L. Their structures were elucidated on the basis of sepectroscopic data and by comparison with those of the related compounds reported in the literature. In addition, the absolute configurations of 2 and 4 were determined by single‐crystal X‐ray diffraction analyses.     

Highly efficient solvent-free catalytic hydrogenation of solid alkenes and nitro-aromatics using Pd nanoparticles entrapped in aluminum oxy-hydroxide

Solid alkenes and aromatic nitro compounds are readily hydrogenated to the corresponding alkanes without further reduction of other functional group and amino compounds in nearly quantitative yields in the presence of Pd nanoparticles entrapped in aluminum oxy-hydroxide under the solvent-free condition.