Cover Picture: A Stepwise Annulation for the Transformation of Cyclic Ketones to Fused 6 and 7‐Membered Cyclic Enimines and Enones (Chin. J. Chem. 4/2019)

The cover picture shows a typical building within the Campus of Xiamen University displaying Chen Jiageng (Tan Kah Kee)'s style. Just like many beautiful buildings designed and constructed by human, Nature “designs and constructs” a huge number of useful molecules with fascinating structures called natural products. Many natural products possess a fused six or seven‐membered carbocyclic unity. On page 315–322, the Huang's group disclosed a three‐step “[2+n]” annulation method for the construction of fused six and seven‐membered carbocyclic enimines and enones. The method starts from simple cyclic ketones and terminal olefinic amides, and relies on both the Suzuki coupling reaction and the olefin‐amide based Friedel‐Crafts type acylating reaction, a method developed by Huang and coworkers.

     

A Novel Dihydroflavone from the Roots of Uvaria Macrophylla

A new dihydroflavone (1), named macrophyllol A, was isolated from the roots of Uvaria macrophylla. Its structure was elucidated on the basis of spectroscopic evidence.     

Esters of 5-carboxyl-5-methyl-1-pyrroline N-oxide: a family of spin traps for superoxide

Apparent rate constants, at acidic pH and neutral pH for the reaction of a family of ester-containing 5-carboxyl-5-methyl-1-pyrroline N-oxides with superoxide (O2*-) were estimated, using ferricytochrome c as a competitive inhibitor. It was of interest to note that the rate constants were similar among the different nitrones and not that significantly different from that found for 5-(diethoxyphosphoryl)-5-dimethyl-1-pyrroline N-oxide. At acidic pH, the rate constant for spin trapping O2*- was 3-fold greater than that at physiological pH. Subsequent experiments determined the half-life of aminoxyls, derived from the reaction of these nitrones with O2*-. The EPR spectra were modeled by using a global analysis method. The results clearly demonstrated that EPR spectra of all the aminoxyls were inconsistent with a model that included a single gamma-hydrogen splitting. A better interpretation modeled them as two diastereomers with identical nitrogen splittings and slightly different beta-hydrogen splittings. Detailed line width analyses slightly favored an equal line width-unequal population ratio for the two diastereomers.     

模式识别—人工神经网络在化学中的若干新应用

本文通过我们应用模式识别－人工神经网络方法预报新化合物、熔盐相图以及复杂化学反应体系的研究，展示应用模式识别－人工神经网络方法与物理化学理论相结合，研究化学现象的可能性和应用价值。     

Novel carboxylated oligothiophenes as sensitizers in photoelectric conversion systems

Novel carboxylated oligothiophenes with different thiophene units were designed and synthesized as photosensitizers in dye-sensitized solar cells (DSSCs) for efficient opto-electric materials. The introduction of -COOH into thiophene molecules can lead to a red shift of UV-visible absorption, increase light-harvesting efficiency, and enhance photoinduced charge transport by forming efficient covalent bonds to the substrate surface. A red shift of the absorption spectrum of oligothiophene is also achieved by the increase in the number of thiophene units. The DSSCs based on the oligomers have excellent photovoltaic performances. Under 100 mW cm(-2) irradiation a short-circuit current of 10.57 mA cm(-2) and an overall energy conversion efficiency of 3.36 % is achieved when pentathiophene dicarboxylated acid was used as a sensitizer. The incident photo-to-current conversion efficiency (IPCE) has a maximum as high as 80 %. In addition, photovoltage and photocurrent transients show that slow charge recombination in DSSCs is important for efficient charge separation and excellent photoelectric conversion properties of the oligomers. These initial and promising results suggest that carboxylated oligothiophenes are efficient photosensitizers.     

Reaction of porous silicon with both end-functionalized organic compounds bearing alpha-bromo and omega-carboxy groups for immobilization of biomolecules

Both end-functionalized (alpha-bromo and omega-carboxy) compounds were first tested for the radical reaction on the silicon-hydride (Si-H) terminated porous silicon (PSi) with/without the presence of diacyl peroxide initiator under microwave irradiation. Then the carboxylic acid monolayers (CAMs) assembled on PSi through the robust Si-C bonds were converted to amino-reactive linker, N-hydroxysuccinimide (NHS)-ester, terminated monolayers. And finally two proteins of bovine serum albumin (BSA) and lysozyme (Lys) were immobilized through amide bonds. The optimum PSi membrane for protein immobilization without collapse, with parameters of porous radii 4-10 nm and depth 0.2-4.6 mum, was prepared from the (100)-oriented p-type silicon wafer. The chemically converted surface products were monitored with Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM).     

The Crystalline Changes of Starch from Rhizoma Dioscorea by Acid Hydrolysis

Dioscoreae (Chinese name Shanyao), the rhizome of various species of genus Dioscorea opposita Thunb.(Dioscoreaceae), has been used as an important invigorant in traditional Chinese medicine (TCM) for many years1. Starch, the most abundant carbohydrate in …     

Cloud Point Extraction Preconcentration of Trace Cadmium as 1-Phenyl-3-methyl-4-benzoyl-5-pyrazolone Complex and Determination by Flame Atomic Absorption Spectrometry

A new method for the determination of trace cadmium in water samples by flame atomic absorption spectrometry (FAAS) after cloud point extraction (CPE) is proposed. The method is based on the complexation of Cd with 1-phenyl-3-methyl-4-benzoyl-5-pyrazolone (PMBP) in the presence of non-ionic micelles of Triton X-100. The effect of experimental conditions such as pH, concentration of chelating agent and surfactant, equilibration temperature and time on cloud point extraction was studied. Under the optimum conditions, the detection limits are 0.64 ng mL^±1 with relative standard deviations (RSDs) of 2.1% (n = 10). The proposed method was applied to the determination of trace cadmium in water samples with satisfactory results.     

Synthesis and screening of a molecularly imprinted polymer library targeted for penicillin G

A library of molecularly imprinted polymers (MIPs) was synthesized by radical bulk polymerization using the beta-lactam antibiotic penicillin G as the template. Diversity of the library was obtained by combining various functionalized monomers and cross-linkers and by varying the stoichiometry and the concentration of the components in the prepolymerization mixtures. The library was screened for selectivity to penicillin G by a radioligand binding assay and was compared to a corresponding control library. The best MIP candidate, showing the highest selectivity for penicillin G, was prepared from methacrylic acid and trimethylolpropane trimethacrylate as the functionalized monomer and cross-linker, respectively. Cross-reactivity studies with other beta-lactam antibiotics showed a low cross-reactivity of penicillin V (15%), ampicillin (16%), and amoxicillin (19%). Nafcillin and oxacillin showed less cross-reactivity (<1%). Cross-reaction with a cephalosporin antibiotic (cephapirin) and structurally nonrelated antibiotics (chloramphenicol, tetracycline, dapsone, and erythromycin) was less than 0.01%.     

Existence in the Large for Pressure-Gradient System

In this paper, the authors use Glimm scheme to study the global existence of BV solutions to Cauchy problem of the pressure-gradient system with large initial data. To this end, some important properties of the shock curves of the pressure-gradient system in the Riemann invariant coordinate system and verify that the shock curves satisfy Diperna’s conditions (see [Diperna, R. J., Existence in the large for quasilinear hyperbolic conservation laws, Arch. Ration. Mech. Anal., 52(3), 1973, 244–257]) are studied. Then they construct the approximate solution sequence through Glimm scheme. By establishing accurate local interaction estimates, they prove the boundedness of the approximate solution sequence and its total variation.