New Phenolic Components from Daphne giraldii

Two new bis‐coumarins, namely daphnogitin ( 1 ), daphnogirin ( 2 ), and a flavan‐3‐ol derivative, 5‐O‐methylafzelechin ( 3 ), together with eleven known compounds, daphnetoxin, 1,2‐dihydrodaphnetoxin, daphnetin, daphnoretin, daphneticin, isodaphneticin, trans‐2,3‐dihydro‐3‐(4‐hydroxy‐3‐methoxyphenyl)‐2‐(hydroxymethyl)‐9H‐pyrano[2,3‐f]‐1,4‐benzodioxin‐9‐one (= demethoxyisodaphneticin; 4b ), (+)‐pinoresinol, acuminatin, (−)‐dihydrosesamin, and isosalicifoline, were isolated from the leaves and stems of Daphne giraldii. Compound 4b was isolated for the first time as a natural product, and 1,2‐dihydrodaphnetoxin, daphneticin, isodaphneticin, (+)‐pinoresinol, acuminatin, (−)‐dihydrosesamin, and isosalicifoline were isolated for the first time from Daphne giraldii. The structures of the three new compounds were elucidated by spectroscopic analysis.     

解微分方程组的改进尤拉方法的改进

对改进尤拉方法解微分方程组的方法作了改进,改进的算法与原来算法的计算量一样,但精度比较高.     

Simultaneous Quantification of Benazepril, Gliclazide and Valsartan in Human Plasma by LC–MS–MS and Application for Rapidly Measuring Protein Binding Interaction between Rhein and These Three Drugs

For new drug candidates with high protein binding in the treatment of diabetic nephropathy, their influence on the protein bindings of angiotensin-converting enzyme inhibitors, sulfonylurea drugs, and angiotensin receptor blockers should be predicted to prevent side effects. To provide an efficient tool for this study, a sensitive and rapid LC–MS–MS method was developed for the simultaneous quantification of representative drugs, benazepril, gliclazide and valsartan in human plasma. Chromatographic separation was performed on a Shim-pack VP-ODS C18 column (250 × 2.0 mm i.d., 5 μm) using methanol–0.05% formic acid (90:10, v/v) as mobile phase. Detection was performed on a triple quadrupole tandem mass spectrometer equipped with an electrospray ionization source and operated in SRM mode. Lower limits of quantification were 2, 2 and 20 ng^?1 mL for benazepril, gliclazide and valsartan with 0.1 mL plasma sample. The method fulfills the precision, accuracy, linearity, sensitivity, selectivity requirements to quantify the three drugs and has been successfully used to studying protein binding of benazepril, gliclazide and valsartan in the presence of rhein.     

Bi2O3 Hierarchical Nanostructures: Controllable Synthesis,Growth Mechanism,and their Application in Photocatalysis

Flower power : Unique 3D flower‐like Bi₂O₃ hierarchical nanostructures were synthesized using a mild aqueous template‐free method (see figure). By introducing VO₃^? into the reaction system, which mediated the nucleation and growth of Bi₂O₃, the in situ self‐assembly of 3D hierarchitectures from 2D nanosheets has been realized.

     

Enantioselective Friedel–Crafts Alkylation of Indoles with Alkylidene Malonates Catalyzed by N,N′‐Dioxide–Scandium(III) Complexes: Asymmetric Synthesis of β‐Carbolines

An efficient catalytic asymmetric Friedel–Crafts alkylation of indoles with alkylidene malonates has been developed by using a chiral N,N′‐dioxide–Sc(OTf)₃ complex as the catalyst (see scheme). Some optically active intermediates containing the indole skeleton have been synthesized, such as indolepropionic acid, tryptamines, and β‐carbolines. The coordination between the scandium atom and the chiral N,N′‐dioxide compound has been revealed by X‐ray structure analysis.

     

Hydroxycinnamic Acids as DNA‐Cleaving Agents in the Presence of CuII Ions: Mechanism,Structure–Activity Relationship,and Biological Implications

The effectiveness of hydroxycinnamic acids (HCAs), that is, caffeic acid (CaA), chlorogenic acid (ChA), sinapic acid (SA), ferulic acid (FA), 3‐hydroxycinnamic acid (3‐HCA), and 4‐hydroxycinnamic acid (4‐HCA), as pBR322 plasmid DNA‐cleaving agents in the presence of Cu^II ions was investigated. Compounds bearing o‐hydroxy or 3,5‐dimethoxy groups on phenolic rings (CaA, SA, and ChA) were remarkably more effective at causing DNA damage than the compounds bearing no such groups; furthermore, CaA was the most active among the HCAs examined. The involvement of reactive oxygen species (ROS) and Cu^I ions in the DNA damage was affirmed by the inhibition of the DNA breakage by using specific scavengers of ROS and a Cu^I chelator. The interaction between CaA and Cu^II ions and the influence of ethylenediaminetetraacetic acid (EDTA), the solvent, and pH value on the interaction were also studied to help elucidate the detailed prooxidant mechanism by using UV/Vis spectroscopic analysis. On the basis of these observations, it is proposed that it is the CaA phenolate anion, instead of the parent molecule, that chelates with the Cu^II ion as a bidentate ligand, hence facilitating the intramolecular electron transfer to form the corresponding CaA semiquinone radical intermediate. The latter undergoes a second electron transfer with oxygen to form the corresponding o‐quinone and a superoxide, which play a pivotal role in the DNA damage. The intermediacy of the semiquinone radical was supported by isolation of its dimer from the Cu^II‐mediated oxidation products. Intriguingly, CaA was also the most cytotoxic compound among the HCAs toward human promyelocytic leukemia (HL‐60) cell proliferation. Addition of exogenous Cu^II ions resulted in an effect dichotomy on cell viability depending on the concentration of CaA; that is, low concentrations of CaA enhanced the cell viability and, conversely, high concentrations of CaA almost completely inhibited the cell proliferation. On the other hand, when superoxide dismutase was added before, the two stimulation effects of exogenous Cu^II ions were significantly ameliorated, thus clearly indicating that the oxidative‐stress level regulates cell proliferation and death. These findings provide direct evidence for the antioxidant/prooxidant mechanism of cancer chemoprevention.     

Magnetic nanocomposites of Fe_3O_4/SiO_2-FITC with pH-dependent fluorescence emission

This paper describes the formation of magnetic and fluorescent nanocomposite particles which consist of superparamagnetic Fe_3O_4 core,SiO_2 shell and organic dye(FITC) coating layer on their surface.The obtained nanocomposites possess typical superparamagnetism and exhibit clear green fluorescence image.And their fluorescence emission is pH-dependent,which would be applied to pH sensing.     

A simple and efficient synthesis of 2-substituted benzothiazoles catalyzed by H_2O_2/HCl

A simple and efficient procedure for the synthesis of substituted benzothiazoles through condensation of 2-aminothiophenol with aromatic aldehydes in the presence of H_2O_2/HCl system in ethanol at room temperature is described.The target compounds have been characterized by ~1H NMR,~(13)C NMR,IR and MS.Short reaction time,easy and quick isolation of the products,and excellent yields are the main advantages of this procedure.     

A new member of the calix[4]crown family:Facile synthesis and characterization of a calix[4]crown-9 cone conformer

25,27-Dipropoxy-p-tert-butylcalix[4]crown-9 cone conformer 5 was readily synthesized via an intramolecular cyclization strategy in good yields.The structures of all the new compounds involved were confirmed by NMR,ESI-MS and elementalanalyses.All of them were proved to be in the cone conformation.