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25 May 2009, Volume 25 Issue 3

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Content of Chemical Research in Chinese Universities Vol.25 No.3(2009)

2009, 25(3):  0. 

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Articles

Synthesis and Crystal Structure of Unprecedented Pentanuclear Cu₅^II Complex Containing both Macrocyclic and Azido Ligands

SUN Ya-qiu*, FAN Lan-lan, GAO Dong-zhao and LIAO Dai-zheng

2009, 25(3):  265-268. 

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The organic-inorganic hybrid complex with formula [(CuL)₂Cu₃(μ-1,1-N₃)₄(ClO₄)₂], complex 1, {CuL, [5,6:14,15-dibenzo-1,4,8,12-tetraazacyclopentadeca-7,13-diene-2,3-dione(2-)]copper(II)}, has been synthesized and structurally determined. The crystals of complex 1 crystallize in the triclinic system with space group P1, a=0.92983(12) nm, b=1.09644(14) nm, c=1.27396(16) nm, α=70.782(2)°, β=86.266(2)°, γ=78.284(2)°. In this complex, the five copper ions are bridged by macrocyclic oxamide groups and azido. Furthermore, C―H···O hydrogen bond interactions link the pentanuclear fragments to form a 2D supramolecular architecture.

Conformation Disturbance of CopC by α-Naphthylamine

LI Hui-qing, ZHENG Xiao-yan, ZHAO Ya-qin and YANG Bin-sheng*

2009, 25(3):  269-272. 

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It is known that urea and guanidine hydrochloride(GuHCl) induce conformational change of proteins in a certain range of molar ratios. In our research, α-naphthylamine(NA) above 10^–4 mol/L at pH 7.0 was discovered to perturb the conformation of CopC, a copper resistant protein with a Greek β-barrel motif; this was reflected by the greater fluorescence quenching and red-shifted emission peak of CopC. The conformation change of CopC was also verified in acrylamide collision experiment by comparing quenching levels of CopC in the presence or the abscence of NA. Comparison of emission change of CopC-Cu²⁺ with that of apo-CopC showed a consistent result with their denaturation in GuHCl. And decreasing fluorescence polarization of CopC with increasing NA concentration is consistent with a more extend conformation of CopC. Interaction mechanism was also explored.

Synthesis and Characterization of Model Complexes of Catechol Dioxygenases Supported by the Anionic Hydrotris-3, 5-dimethyl-pyrazolylborate Ligand

A Li-ta, DUAN Li-mei*, XU Xiu-ting and LIU Shu-qin

2009, 25(3):  273-278. 

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An iron(III) complex [Fe^III(Tpz^Me2)(Hpz^Me2)Cl₂](1) has been synthesized at a low temperature, which contains tripodal ligand, namely, the anionic hydrotris-3,5-dimethyl-pyrazolylborate(Tpz^Me2). A series of iron(III) catecholate complexes 2―5 has been obtained via the reaction of compound 1 with catecholate or substituted catecholates. These complexes were characterized by X-ray crystallographic analysis, mass spectrometry and elemental analysis, and the results show that TpzMe₂ ligand has the beneficial effect on the stabilization of iron(III) catecholate complexes.

Novel Metal-organic Framework Compound Pb(C₅H₄NCOO)₂ Showing One-dimensional Channel Defined as Four Leads and Four Nicotinic Acids

XU Xiao-yu, ZHOU Rui-sha, SONG Jiang-feng and XU Ji-qing*

2009, 25(3):  279-281. 

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A novel metal-organic framework(MOF) compound of Pb(C₅H₄NCOO)₂ was hydrothermally synthesized and structurally determined by X-ray single-crystal diffraction. The data of unit cell: orthorhombic space group Pccn, a=1.0325(2) nm, b=1.3597(3) nm, c=0.8499(2) nm, V=1.1931(4) nm³, Z=4, D_c=2.513 g/cm³, R₁=0.047 were obtained on the basis of 1365 reflections with F_o>2σ(F_o). PbN₂O₆ polyhedron adopts the distorted cubic configuration which is assigned to the holodirected geometry. These PbN₂O₆ polyhedra can form the zigzag chain by edge-sharing mode along(001) direction. Pb atom is connected by six nicotinic acid molecules, leading neutral 3D metal-organic framework with a channel defined by four Pb atoms and four nicotinic?acid molecules.

Layer Zirconogermanate——(H₂DETA)[ZrGe₃O₈F₂] Showing Odd 3MR and 7MR

LI Ya-feng*, SUN Jin-xu, WU Lei-lei, TIAN Yong, WANG Dao-wu, ZHANG Long, ...

2009, 25(3):  282-285. 

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A layered zirconogermanate, (H₂DETA)[ZrGe₃O₈F2](1), was hydro(solvo)thermally synthesized with diethylenetriamine(DETA) as template, and structurally determined by X-ray single-crystal diffraction. Compound 1 crystallized in the monoclinic space group P2₁/c with data of unit cell: a=0.7644(2) nm, b=1.1235(2) nm, c=1.6860(3) nm, V=1.4479(5) nm³, μ(Mo Kα)=6.931 mm^–1, Z=4, R₁=0.0402 for 3236 reflections with F_o>2σ(F_o). The structure of compound 1 was formed by alternatively packing the inorganic layer of ZrGe₃O₈F₂ and H₂DETA templated molecules along (001) direction. It was worth pointing out that the odd bifurcated 7MR nets were surrounded by odd 3MR. The protonated and disordered H₂DETA cations not only balanced the superfluous charges of framework but also stabilized the structure of compound 1 by the hydrogen bond between ―NH₃ group and oxygen on the framework. Furthermore, IR and TG were utilized to characterize the structure and thermal stability, respectively.

Synthesis and Catalytic Properties of ZSM-5 Zeolite with Alkyl-polyamine Triethylene-tetramine as Directing Agent

WEI Bo*, SUN Jian-min, CAO Hui-qun, Lü Yu-juan and FANG Lin

2009, 25(3):  286-290. 

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With alkyl-polyamine triethylene-tetramine as the structure-directing agent, aluminosilicate zeolite ZSM-5(MFI) crystals were synthesized and characterized by XRD, SEM, FTIR, and TG-DTA. The results indicate that the organic amine has a certain influence on the crystal shape and size. The alkaline condition was in favor of the crystallization of ZSM-5 zeolite in the triethylene-tetramine system. The catalytic activity of as-synthesized crystals was examined for the aqueous hydroxylation of phenol with hydrogen peroxide. The phenol conversion was 13.6%, and the selectivities of the as-synthesized samples for catechol, hydroquinone, and benzoquinone were 66.0%, 23.6%, and 10.4%, respectively. The as-synthesized ZSM-5 sample shows a relatively high selectivity towards catechol and could be a promising catalyst.

Interaction Between Mitoxantrone Metal Complex and Titan Yellow by Resonance Rayleigh Scattering Spectra and Its Analytical Application

HU Rong, YANG Qiong, ZHANG Shu-ran and YANG Ji-dong*

2009, 25(3):  291-296. 

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In a pH 2.4 Britton-Robinson buffer medium, the anthracycline antibiotics mitoxantrone(MXT) could react with metal ions such as Pd(II), Co(II) and Cu(II) to form 1:2(molar ratio) cationic chelates, which further reacted with the anionic dye titan yellow to form 1:2 ternary ion-association complexes by electrostatic interaction. As a result, the intensity of resonance Rayleigh scattering(RRS) was enhanced greatly. These RRS spectral characteristics of various metal ion systems were similar, and the maximum RRS wavelengths were all located at 454 nm. But the increments of RRS intensities were different in the series of Pd(II)>Co(II)>Cu(II). The enhanced RRS intensities were proportional to the concentration of MXT in a range of 0.03―2.4 μg/mL and the detection limit(3σ) was 0.009 μg/mL for the Pd(II) system. In this study, the optimum conditions of the reactions and the effects of foreign substances were investigated, in addition, the composition and reaction mechanism of ion-association complexes were discussed. Thus a highly sensitive, simple and rapid method is proposed for the determination of MXT in urine and serum samples.

Determination of Saponins in Leaf of Panax Ginseng C. A. Mey. by High Performance Liquid Chromatography

LIU Gui-ying, ZHOU Hong-yu, LU Juan, ZHU Na, GUI Ming-yu, JIN Yong-ri, ......

2009, 25(3):  297-301. 

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A high performance liquid chromatography(HPLC) with UV detection was established for simultaneous determination of saponins in the leaf of Panax ginseng C. A. Mey. Nine ginsenosides(Rb₁, Rb₂, Rb₃, Rc, Rd, F1, F2, F3, F5) and notoginsenoside Fe(NFe) were studied. Among the saponins, the ginsenosides F1, F2, F3, F5 and NFe were determined by HPLC-UV method for the first time. The determination of the ginsenosides via the HPLC-UV method was performed on a reversed-phase C₁₈ column with gradient elution in 40 min. The linearity, precision, accuracy, and detection limit for determining the saponins were studied and the samples from different areas in China were analyzed. The HPLC-ESI-MS was used to identify the saponins. The results indicate that the HPLC-UV provided a good accuracy, reproducibility and sensitivity for the determination of the ten saponins.

Dynamic High Pressure Micro-fluidization Effects on Structure and Physico-chemical Properties of Egg White Protein

TU Zong-cai*, WANG Hui, LIU Cheng-mei, LIU Guang-xian, CHEN Gang......

2009, 25(3):  302-305. 

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The authors dealt with the effects of dynamic high pressure micro-fluidization(untreated and 20―160 MPa treated) on the structure and physico-chemical properties of egg white solutions[6%(mass fraction) or 61.2 mg protein/mL]. Micro-fluidization treatment resulted in a decrease in mean particle size, and little change in solubility. It was found that the residual denaturation enthalpy was decreased with the increase of pressure from 20 to 100 MPa and from 120 to 160 MPa, reaching into the maximum at 160 MPa. There was an increase of surface hydrophobicity with the maximum at 100 MPa observed. Simultaneously, micro-fluidization treatment also resulted in a decrease in the content of sulfhydryl groups.

Effect of Ionic Liquid on Retention of Solutes on C₁₈ Column Based on Linear Solvation Energy Relationships

TIAN Ming-lei and ROW Kyung Ho*

2009, 25(3):  306-311. 

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Several chromatography systems with ionic liquids and a mixture of water with the modifier as mobile phase were characterized via the linear solvation energy relationships(LSER) model. The effects of the ionic liquids and modifier(methanol) concentrations on the retention of 10 solutes(caffeine, pyridine, aniline, phenol, methylparaben, acetopenone, m-cresol, p-cresol, o-cresol, and benzene) were discussed. The LSER model demonstrated high potential to predict retention factors with high squared correlation coefficients(r²>0.97). A comparison of predictable and experimental retention factors revealed that LSER can adequately reproduce the experimental retention factors of the solutes under different investigated experimental conditions. This model is a helpful tool to evaluate the retention characteristics of ionic liquid systems and to understand the interactions of solutes and ionic liquids.

Novel Efficient Method for Synthesis of N_1,4-Disubstituted-1,4-benzodiazepine-2,5-diones

WANG Qiu-yan, YU Jing-jun, LU Cui-fen*, CHEN Zu-xing and YANG Gui-chun

2009, 25(3):  312-316. 

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A novel and efficient method was developed for the liquid-phase synthesis of N_1,4-disubstituted-benzodiazepine-2,5-diones with 2-chloro-5-nitrobenzoic acid as initiating material via 4 step reactions containing  esterification, “Ulmn reaction”, acylation, alkylation and cyclization. The reaction conditions were mild and the overall yields of the products ranged from 45% to 71%.

Photophysical Behavior of Heteroduplexes Formed from Naphthalene Incorporated Foldamers, and Linear Donors and Pyromellitic Diimide Incorporated Foldamers

ZHAO Shu-min, GU Hai-ning and ZHOU Qi-zhong*

2009, 25(3):  317-327. 

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The authors synthesized the electron-rich 1,5-dioxonaphthyl group incorporated foldamers, and linear donors and electron-deficient pyromellitic diimide incorporated foldamers, which were investigated in organic solvents. There is an evident charge transfer process from the donors to the electron-deficient foldamers, due to the donor-acceptor interaction of the heteroduplexes formed from the donors and the electron-deficient foldamers in chloroform, observed by using the ultraviolet(UV) visible method. The charge transfer process of the heteroduplexes depends on the molecular structure(not only the number of 1,5-dioxonaphthyl groups and pyromellitic diimide groups in the heteroduplex, but also the intermolecular double hydrogen bond in the heteroduplex), the intercalative π-π sta- cking motif, the initial concentration of heteroduplexes, and the polarity of the solvent. Fortunately, the authors found a critical bumping concentration(CBC) of the donors in acetonitrile or chloroform, which is useful in quantitative research, by using the fluorescence method. The value of CBC depends not only on intramolecular folding and the intramolecular hydrogen bond, but also on intramolecular π-π stacking and the solvent. The electron-deficient foldamers quenched the fluorescence of the donors. Fluorescence quenching depends not only on the number of pyromellitic diimide groups and 1,5-dioxonaphthyl groups in the heteroduplex, but also on the intercalative π-π stacking motif between the donor and the acceptor.

Constituents from Aerial Parts of Bidens ceruna L. and Their DPPH Radical Scavenging Activity

ZHU Na, LI Xu-wen, LIU Gui-ying, SHI Xiao-lei, GUI Ming-yu, SUN Chang-qing......

2009, 25(3):  328-331. 

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A new chalcone glycoside, butein-4-methoxyl-4'-O-(6''-O-acetyl)-β-D-glucopyranoside(2), along with seven known compounds, namely, quercitrin(1), luteolin-7-O-β-D-glucopyranoside(3), butein-4'-O-β-D-glucopyranoside(4), butein-4-methoxyl-4'-O-β-D-glucopyranoside(5), butin-7-O-β-D-glucopyranoside(6), isoquercitrin(7), and sulfurein(8) was isolated from aerial parts of Bidens ceruna L. Their structures were elucidated on the basis of spectroscopic studies. Compounds 1―8 were tested for their DPPH radical scavenging activity and, except compounds 2 and 5, other compounds showed scavenging activity.

Design, Synthesis, and Biological Evaluation of 5H-Thiazolo[3,2-a]pyrimidine-6-carboxylic Acid Ethyl Ester Derivatives as a Novel Series of Acetylcholinesterase Inhibitors

ZHI Hui, CHEN Lan-mei, ZHANG Lin-lin, LIU Si-jie, David Chi Cheong WAN......

2009, 25(3):  332-337. 

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Acetylcholinesterase inhibitors are the most frequently prescribed anti-Alzheimer’s drugs. A series of 5H-thiazolo[3,2-a]pyrimidine-6-carboxylic acid ethyl ester derivatives as the novel acetylcholinesterase inhibitors was designed based on virtual screening methods. The target compounds were synthesized with Biginelli reaction and Hantzsch-type condensation of dihydropyrimidines with substituted phenacyl chlorides, and were characterized with elemental analysis, IR, MS, ¹H NMR, and ¹³C NMR. The biological evaluation against human acetylcholinesterase  in vitro indicated all the target compounds show more than 50% inhibition at 10 μmol/L by means of the Ellman method. The results provide a starting point for the development of novel drugs to treat Alzheimer’s disease and lay the foundation of searching for improved acetylcholinesterase inhibitors with the novel scaffolds.

Synthesis of 2,4-Diarylcyclooctenopyridines with One-pot Four-component Reactions

WANG Qi-fang and YAN Chao-guo*

2009, 25(3):  338-342. 

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An efficient one-pot four-component reaction has been developed for the synthesis?of 2,4-diarylcyclooc- tenopyridines, in moderate yields. This route is an effective modified two-step synthesis of Kröhnke pyridine and involves a four-component tandem reaction of pyridinium bromide with aromatic aldehydes and cyclooctanone in a system of NH4OAc/HOAc under microwave irradiation.

Iodine-catalyzed Efficient Synthesis of β-Keto Esters from Aldehydes and Ethyl Diazoacetate Under Solvent-free Conditions

WANG Hong-she* and ZENG Jun-e

2009, 25(3):  343-346. 

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An efficient procedure for the synthesis of β-keto esters from the reaction of aldehydes and ethyl diazoacetate catalyzed by iodine at room temperature under solvent-free conditions has been described. The catalytic procedure has the advantages of easily available catalyst, mild reaction conditions, high yields, and easy work-up.

Adjuvant Effects of Dual Co-stimulatory Molecules on Cellular Responses to HIV Multiple-epitope DNA Vaccination

SHEN Zhen-wei, JIN Hong-tao, LI Chang, CONG Yan-zhao, NAN Wen-long......

2009, 25(3):  347-352. 

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Designing adjuvants that can induce strong cytotoxic T cell responses is largely required for preparing DNA vaccines. In this study we explored dual costimulatory molecules 4-1BBL and OX40L as adjuvants to improve the efficiency of the HIV multiple-epitope DNA vaccine. When explored in the human dendritic cell-T cell based coculture system, dual costimulatory molecules significantly enhanced the anti-HIV T cell response of the HIV multiple-epitope DNA vaccine, as detected by intracellular cytokine staining to HIV antigens, cytokines accumulation in the cultures, and antigen-specific cytotoxic T lymphocyte responses. These results suggest that dual costimulatory molecules 4-1BBL and OX40L can effectively increase the potential of the HIV multiple-epitope antigen DNA vaccine and may provide an exciting approach for HIV therapy.

Study on a Specific Site Tyr⁴⁴⁴ on a Hyperthermophilic Enzyme APE1547

RAO Lang, BI Yun-feng, XIE Gui-qiu, ZHANG Fei, WANG Yan, CAO Shu-gui......

2009, 25(3):  353-356. 

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Hyperthermophilic enzyme APE1547 is an extremely thermostable recombinant protein from thermophilic archaeon Aeropyrum pernix K1. The Tyr⁴⁴⁴ located in the catalytic domain adjacent to the catalytic amino acid Ser⁴⁴⁵ and formed hydrogen bond with Ile⁵⁶⁷. To study the effect of Tyr⁴⁴⁴ on the activity of APE1547, site-directed mutagenesis was applied. Two mutant enzymes T444S and T444G were created. Comparison of the mutant enzymes with wide enzyme, the thermostability of mutants T444S and T444G decreased by 10%―20%, but the catalytic efficiency of mutants toward pNPC8 and Ac-Leu-pNA increased 1.33 and 1.75 fold respectively. Molecular modeling shows that the elimination of hydrogen bond between Tyr⁴⁴⁴ and Ile⁵⁶⁷ is the cause of the decrease in thermostability and increase in catalytic efficiency. These observations suggest that Tyr⁴⁴⁴ plays an important role in the catalytic ability and thermostability of this enzyme.

Molecular Cloning and Expression Analysis of an Actin Gene from Chinese Licorice(Glycyrrhiza uralensis Fisch)

WANG Fang, DONG Le* and YUAN Jian-jun

2009, 25(3):  357-361. 

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A PCR-based homologous cloning strategy was used to identify an actin gene from the roots of Chinese licorice(Glycyrrhiza uralensis Fisch). Results of sequence analysis indicate that a 1137 bp cDNA with an open reading frame encoding 377 amino acids, actin ortholog, GuActin, was successfully cloned and characterized(GenBank accession No. EU190972). Thus far, GuActin is the first actin of Chinese licorice that has been identified at a molecular level. Analysis by Northern blot shows that GuActin was expressed strongly in the roots, particularly in radicles than in stems and leaves. These results suggest that GuActin may be a member of the vegetative subfamily of the actin family.

Fluorescence-quenching of Tryptophan Ion-18-crown-6 Complex——A Different Observation from Its Neutral Counterpart

YU Qing, CAO Jie*, LIU Tao and WANG Zhi-xiang*

2009, 25(3):  362-367. 

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It is well-known that primary amines form inclusive complexes with crown ethers. This kind of noncovalently inclusive complexes, exemplified tryptophan complex with 18-crown-6, was studied by combination of two experimental methods, fluorimetry and mass spectrometry, with theoretical calculation. Fluorescence intensity of tryptophan in the absence and the presence of 18-crown-6 in aqueous HAc-NaAc buffer solution at pH=3.73 has been studied by fluorometry. The fluorescence intensity decreases significantly with increasing the concentration of 18-crown-6. The association constant K for the 1:1 complex of tryptophan ion-18-crown-6 was determined by means of fluorimetry. Mass spectrometric study of the complex gives direct evidence of the complex in the gas phase whose structure and binding energy are properly predicted by ab initio calculation.

Synthesis of Mesoporous Carbon Monolith by Direct Carbonization of Compressed Sucrose/Silica Composite

LIU Yu, LIU Gang*, XU Yue, ZHANG Wen-xiang, WU Shu-jie and JIA Ming-jun*

2009, 25(3):  368-372. 

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Mesoporous carbon monolith was synthesized by the direct carbonization of compressed sucrose/silica composite, which was prepared by using sol-gel method. The structural and textural properties of the materials were investigated by XRD, DRIFT, N₂-adsorption and SEM. The characterization study shows that the resultant carbon monolith possesses a relatively high surface area, large pore volume and well interconnected pore system. Addition of a certain amount of citric acid or aluminum nitrate into the sol-gel precursor of sucrose/silica composite could considerably change the structure parameters of the carbon monolith.

Studies of Solvent Effects on Structure and Low Frequency Vibrational Spectra of 2,4-Dinitrotoluene

WANG Lin, JIN Ming-xing, LIU Hang and DING Da-jun*

2009, 25(3):  373-376. 

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Solvent effects on 2,4-dinitrotoluene(2,4-DNT) molecule in different solvents(toluene, ethanol, and water) were studied via DFT PCM method at B3LYP/6-311+G(d,p) level. The influences of these solvents on the molecular structure, vibrational spectra, charge distribution, and dipole moment were studied as well. The results show that PCM computations are successful in describing the vibrational spectra of 2,4-DNT molecules in these solutions and the solvent effects on the low frequency vibrational spectra are weak.

Adsorption of Benzene and Propylene in Zeolite ZSM-5: Grand Canonical Monte Carlo Simulations

SUN Xiao-yan, LI Jian-wei*, LI Ying-xia, YAN Shi-cheng and CHEN Biao-hua

2009, 25(3):  377-382. 

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The adsorption behavior of benzene and propylene in zeolite ZSM-5 was studied by Grand Canonical Monte Carlo(GCMC) simulations. It could be found that benzene and propylene molecules showed different adsorption behavior in the zeolite cavities. The loadings of propylene were significantly larger than those of benzene at 100 kPa. From the figures of potential energy distribution, the potential energy of benzene/zeolite was more negative than that of propylene/zeolite, so benzene could be adsorbed more stably than propylene. When the temperature was increased from 298 to 443 K at 100 kPa, the loading of propylene was reduced from 99 to 82 molecules, whereas that of benzene changed little. When benzene and propylene were adsorbed in zeolite simultaneously, the competitive adsorption of them occurred; therefore, the potential energy distribution could be changed significantly. Besides, the adsorption isotherms of benzene and propylene in ZSM-5 at 298 and 443 K were simulated. The results exhibit that the different factors influenced the molecular adsorption at various temperatures and pressures, leading to the diffe- rent rules for the adsorption of benzene and propylene molecules in the zeolite. At a low pressure, the unfavorable energy of propylene/zeolite and the “commensurate freezing” phenomenon of benzene would make the loadings of itself higher than those of propylene. When pressure was higher than 5 kPa, the adsorption of benzene in ZSM-5 would nearly reach saturation.

Synthesis, Crystal Structure and Nonisothermal Kinetics of Complex Co(tda)(5-mphen)(H₂O)

2009, 25(3):  383-387. 

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The title complex, formulated as Co(tda)(5-mphen)(H₂O)(H₂tda=thiodiglycolic acid, 5-mphen= 5-methyl-1,10-phenanthroline), was synthesized and characterized by elemental analysis, IR spectroscopy, X-ray single crystal diffraction, and TG-DTG techniques. The complex crystallized in monoclinic space group C2/c, with parameters of a=1.8142(2) nm, b=0.78251(9) nm, c=2.4624(3) nm, β=93.809(2)°, V=3.4880(7) nm³, Z=8, D_c=1.579 g/cm³, the final R indices [I>2σ(I)] are R₁=0.0469, wR₂=0.1021, R indices for all data are R₁=0.0835, wR₂=0.1169. The central Co²⁺ cation is coordinated in a distorted octahedral geometry with the ligand tda, 5-mphen, and water molecule. The coordination complex possesses a three-dimensional framework by means of hydrogen bonds and π-π stacking interactions. According to TG-DTG curves, the possible thermal decomposition mechanisms, the possible kinetic parameters, and equation of dehydration stage of the complex are obtained, that is, E_a=110.98 kJ/mol, lg(A/s^–1)=8.554, dα/dT = 10^8.5546/β·3(1–α)[–ln(1–α)]^2/3·exp(–13349/T), respectively.

Theoretical Studies on Structures and Electron Affinities of 5- and 6-Halouracils

WANG Hui-ping, XU Wen-guo and ZHANG Hong-xing*

2009, 25(3):  388-396. 

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The molecular structures and electron affinities of 5- and 6-halouracils(XU, X=F, Cl, Br) were determined by means of five different density functional methods. The basis set used in this work is of double-ζ plus polarization(DZP) quality with additional diffuse s- and p-type functions, denoted DZP++. The geometries were fully optimized with each density functional theory(DFT) method, and discussed. Three different types of the neutral-anion energy separations reported in this work are the adiabatic electron affinity(AEA), the vertical electron affinity(VEA), and the vertical detachment energy(VDE). An excellent agreement between our B3LYP results and those obtained by other calculations regarding the structural modifications and electron affinities of neutral and anion 5XU was found. The differences in charge distribution between uracil and halogenated uracils were indicated, thus the ability to form the hydrogen bonds of halogenated uracils was discussed. It shows the applicability of the DFT/DZP++ method to predict the similar molecular models at a highly economical computational cost.

Ring-opening Copolymerization of Adipic Anhydride and Propylene Oxide Catalyzed by Yttrium Triflates

CHEN Feng, ZHU Wei-pu* and SHEN Zhi-quan*

2009, 25(3):  397-399. 

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The ring-opening copolymerization of adipic anhydride with propylene oxide was carried out with yttrium triflates as a catalyst. Poly(propylene adipate) could be synthesized by controlling the copolymerization conditions. The copolymerization procedure was tracked by ¹H NMR analyses.

Facile Route to Aromatic Hyperbranched Poly(ester amines)

ZHANG Zheng-hui and SHI Wen-fang*

2009, 25(3):  400-403. 

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The aromatic hyperbranched poly(ester amines)(AHPEAs) were successfully synthesized via the mild condensation of N-4-cyanobenzyl diethanolamine hydrogenchloride as an AB₂ monomer in concentrated HCl. The polymerization was monitored by FTIR to suppose the reasonable reaction mechanism. The degree of branching was determined to be 0.55 by ¹H NMR with an increased conversion of up to 96%. The glass transition temperature was measured by differential scanning calorimetry to range from –19 to 15 °C. The molecular weights and polydispersities were investigated by gel permeation chromatography.

Letter

Triterpene Acids from Cynoglossum amabile

XU Qing-jun, ZHANG De-zhi*, DANG Li-juan and LI Kun-ping

2009, 25(3):  404-406. 

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A new triterpene acid 2α,3β-dihydroxyolean-12-en-23,28,30-trioic acid, named as amabilic acid(1) was isolated from a water extract of the herbs of Cynoglossum amabile Stapf et Drumm, along with two known triterpene acids, 2α,3β,19α,23-tetrahydroxyolean-12-en-28-oic acid(2) and 21-O-β-D-glucopyranosyl-2α,3β,21β,23-tetrahydr oxyolean-12-en-28-oic acid(3). Their structures were elucidated on the basis of spectroscopic methods and by comparison with literature data. they were reported for the first time from Cynoglossum genus.