Coronal multi-walled silicon nanotubes

By means of first-principles density functional theory(DFT) calculations and molecular dynamics(MD) simulations,a series of coronal multi-walled silicon nanotubes(MWSiNTs) without or with hydrogen terminations are systematically identified.Notably,coronal MWSiNTs,where the interaction between the walls is preferable through covalent bonds rather than weak interaction,show better stability than CNT-like SiNTs. Moreover,they exhibit good elasticity with small Young’s modulus.The investigation of the electronic structure demonstrates that they present metallic characteristics,which is in striking contrast to bulk silicon.Thus,the MWSiNTs may find important applications in electronic devices.     

Solvent effects on oxygen atom transfer reaction between manganese(V)-oxo corrole and alkene

Pseudo-first order reaction rate constants of 5,10,15-tris（pentafluorophenyl）corrole Mn（V）-oxo (F₁₅CMn（V）-oxo),5,15-bis（pentafluorophenyl）-10-（phenyl）corrole Mn（V）-oxo(F₁₀CMn（V）-oxo),5,15- bis（phenyl）-10-（pentafluorophenyl）corrole Mn（V）-oxo（F₅CMn（V）-oxo） and 5,10,15-tris（phenyl）corrole Mn（V）-oxo（F₀CMn（V）-oxo） with a series of alkene substrates in different solvents were determined by UV-vis spectroscopy.The results indicated that the oxygen atom transfer pathway between Mn（V）-oxo corrole and alkene is solvent-dependent.     

Two novel fluorescent calix[4]arene derivatives with benzoazole units in 1,3-alternate conformation for selective recognition to Fe~(3+) and Cr~(3+)

Two novel fluorescent calix[4]arene derivatives 1a and 1b with benzoxazole or benzothiazole units in 1,3-alternate conformation have been synthesized and characterized by IR,~1H NMR,~(13)C NMR and MS.Their complexation properties to different heavy and transition metal ions have been studied by UV-vis spectroscopy and fluorescence spectrometer.Compounds 1a and 1b show selective recognition to Fe~(3+) and Cr~(3+).     

A new macrolide and glycosides from the stem of Sargentodoxa cuneata

A new macrolide glycoside,cuneataside F was isolated from the n-butanol extract of the stem of Sargentodoxa cuneata. The structure was elucidated on the basis of extensive 1D and 2D NMR as well as HRESI-MS spectroscopic analysis.     

Electroanalysis and simultaneous determination of dopamine and epinephrine at poly(isonicotinic acid)-modified carbon paste electrode in the presence of ascorbic acid

A carbon paste electrode modified with electropolymerized fills of isonicotinic acid was developed.The modified electrode shows excellent electrocatalytic activity toward the oxidation of both dopamine(DA)and epinephrine(EP).Separation of the reduction peak potentials for dopamine and epinephrine was about 357 mV in pH 5.3 phosphate buffer solution(PBS)and the character was used for the detection DA and EP simultaneously.The peak currents increase linearly with DA and EP concentration over the range of 8.0×10-5 to 7.0×10-4 mol/L and 5.0×10-6 to 1.0×10-4 mol/L with detection limits of 2 × 10-5 and 1×10-6 mol/L,respectively.The interference studies showed that the modified electrode exhibits excellent selectivity in the presence of large excess of ascorbic acid(AA).     

Cytotoxic triterpenoid saponins from Ardisia pusilla

A new triterpenoid saponin,3-O-{β-D-xylopyranosyl-(1→2)-β-D-glucopyranosyl-(1→4)-[β-D-ghcopyranosyl-(1→2)]-α-L-arabinopyranosyl }-3β,16α,28α-trihydroxy-1313,28-epoxy-oleanan-30-al(ardipusilloside Ⅲ,1),together with two known sapo-nins,ardisiacrispins A(2)and B(3),were isolated from the whole plants ofArdisia pusilla A.DC.Their structures were elucidated by extensive spectral analysis and chemical evidences.Saponins 1 and 3 exhibited significant cytotoxicity against human glioblastoma U251MG cells.     

Determination of sulfur anions by ion chromatography-postcolumn derivation and UV detection

A novel method for determination of formaldehyde sulfoxylate,sulfite,thiocyanate,and thiosulfate in foodstuffs by ion chromatography separation with postcolumn derivation and UV detection has been developed.All species are separated at Dionex IonPac AG22A and AS22A with mobile phase of a mixture of 4.5 mmol/L sodium carbonate and 0.8 mmol/L sodium bicarbonate at a flow-rate of 1.0mL/min.The postcolumn derivation solution was 0.24%iodine in 0.2%phosphate acid and the detection wavelength was set at 288 nm...     

Cytotoxic terpenes from Abies sibirica

One new and 16 known compounds were isolated from Abies sibirica.Their structures were assigned mainly on the basis of NMR and MS spectroscopic data.In bioassay for anti-proliferative activity against four human tumor cells,compound 7 exhibited selective anti-proliferative activity against COLO-205 tumor cell with an IC₅₀ value of 0.9μg/mL.     

H_2SO_4-SiO_2:Highly efficient and novel catalyst for the Ferrier-type glycosylation

<正>Sulfuric acid immobilized on silica gel is designed as a very useful catalyst for synthesis of 2,3-unsaturated glycopyranosides. This handy,metal-free,environment friendly transformation provides high yields andα-stereoselectivities in a very few amount (0.02 eq.) of catalyst and in short reaction times(10 min).     

Synthesis and Biological Activity of a Series of Novel N‐Substituted β‐Lactams Derived from Natural Gallic Acid

A series of novel β‐lactams derived from natural gallic acid were conveniently synthesized via classical Staudinger ketene‐imine cycloaddition reaction. Their structures were confirmed by satisfactory analytical and spectroscopic methods. The preliminary bioassay showed that some of the target compounds exhibited obvious insecticidal activity against Heliothis armigera at the dosage of 0.2 mg/mL.