Mechanism for the inhibition of the acid degradation of ampicillin by 2-hydroxypropyl- β -cyclodextrin

The formation of inclusion complexes between amoxicillin (AMPC) and 2-hydroxypropyl-β-cyclodextrin (HPCD) was investigated by isothermal microcalorimetry and molecular dynamics simulation to evaluate the inhibitory effects on the degradation of AMPC in aqueous solutions at various pH. The process depended significantly on the ionic species of AMPC in the solution. In a strong acid solution, cationic AMPC and HPCD formed two different types of inclusion complexes with a 1:1 stoichiometry: the first-type had a high association constant K ₁ of 4.0-8.0·10³ M^-1 and included the penam ring of AMPC in the HPCD cavity (Mode I), while the second-type with a K ₂ of 1.0·10³ M^-1 contained the phenyl group of AMPC (Mode II). Furthermore, a complex with a 1:2 (AMPC:HPCD) stoichiometry was realized in a two-step reaction and was characterized by a smaller K _1:2of 4.0·10² M^-1 and larger negative enthalpy and entropy changes than the complexes with a 1:1 stoichiometry. Since the β-lactam ring of AMPC could be protected by inclusion with HPCD in the 1:2 complex and Mode I of 1:1 complexes, the degradation of AMPC in the presence of HPCD was approximately four times slower than in its absence at pH 1.2 and 37°C. In weak acid and neutral solutions, zwitterionic AMPC and HPCD formed only one type of inclusion complex with a 1:1 stoichiometry, where the phenyl group was included (Mode II). AMPC was very stable in these solutions (t _1/2=226 h at pH=6.0) and there is little significant difference in the degradation rate between complexed AMPC and uncomplexed AMPC. Thus, the results indicated that the inclusion complex of AMPC with HPCD, effectively increasing the stability of AMPC in a strong acidic solution like that the stomach, would be useful for eradicating Helicobacter pylori infection and as a drug delivery system. This revised version was published online in July 2006 with corrections to the Cover Date.     

Crystal Structure of [Cd（pom）2Cl2]

ＣｒｙｓｔａｌＳｔｒｕｃｔｕｒｅｏｆ［Ｃｄ（ｐｏｍ）_２Ｃｌ_２］ＷｕＷｅｎ－Ｓｈｉ（ＤｅｐａｒｔｍｅｎｔｏｆＣｈｅｍｉｓｔｒｙ，Ｈｕａ－ｑｉａｏＵｎｉｖｅｒｓｉｔｙ，Ｆｕｊｉａｎ，Ｃｈｉｎａ，３６２０１１）ＤｏｎｇＭｅｉ－Ｂｉｎ；ＬｉＳｏｎｇ－Ｘｉａ...     

Hydroxypropyl chitosan bearing beta-cyclodextrin cavities: synthesis and slow release of its inclusion complex with a model hydrophobic drug

Hydroxypropyl chitosan-graft-carboxymethyl beta-cyclodextrin (HPCH-g-CM beta-CD) was synthesized by grafting CM beta-CD onto HPCH using water soluble 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide (EDC) as the condensing agent. Due to the presence of hydrophobic beta-CD rings onto the HPCH backbone, this polymer can be used as a matrix for controlled drug release. The adsorption of a hydrophobic model drug, ketoprofen, by HPCH-g-CM beta-CD microparticles (using tripolyphosphate as an ionic crosslinking agent) fitted well in the Langmuir isotherm equation. The drug dissolution profile showed that HPCH-g-CM beta-CD microparticles provided a slower release of the entrapped ketoprofen than chitosan, and the release behavior was influenced by the pH value of the medium. These results suggest that beta-CD grafted with chitosan derivatives may become a potential biodegradable delivery system to control the release of hydrophobic drugs with pH-responsive capability.     

两个双核铁（Ⅲ）和三足配体的配合物的合成和晶体结构

运用三足四齿配体三（2－甲基吡啶）胺（TPA）或三（2－甲基苯丙咪唑）胺（TBA）,得到两个双核铁(III)配合物，[Fe₂L₂(μ₂-O)(μ₂-p-NH₂-C₆H₄COO)]³⁺ (L = TPA, 1 和 L = TBA, 2)。两个配合物均为单斜晶系，空间群为P2(1)/c.晶胞参数 1: a = 1.4529(4), b = 1.6622(5), c = 2.0625(6) nm, β= 100.327(5)º, V = 4.900(3) nm³, z = 4, F(000) = 2344, 分子量M_r = 1142.91, Dc = 1.549 g/cm³, R₁ = 0.0544, R₂ = 0.0962. 2: a = 1.3378(4), b = 2.1174(7), c = 2.4351(7) nm, β= 97.315(6)º, V = 6.842(4) nm³, z = 4, F (000) = 3116, 分子量M_r = 1505.08, Dc = 1.444 g/cm³, R₁ = 0.0793, R₂ = 0.1623. 在两个双核铁(III)配合物中，中心的三价铁和配体TPA或TBA上的四个氮原子和两个氧原子通过不同的桥形成一个畸变的八面体构型。     

Electrochemical approaches to generation of phosphinidene complexes of tungsten pentacarbonyl

An alternative approach to synthesis of electrophilic terminal phosphinidene complexes of tungsten pentacarbonyl with various substituents at the phosphorus atom has been developed. The approach is based on the reaction of the electrochemically generated tungsten pentacarbonyl ion with trivalent phosphorus acyl chlorides. Electrochemical reduction of ethyldichlorophosphines in the presence of α-diimines is a one-step process that forms 1,3,2-diazaphospholenes containing an exocyclic P-C bond.     

Crystal Structure and Ethylene Oligomerization Catalytic Activity of {2-Carbethoxy-6-[1-[（2,6-diethylphenyl）imino]ethyl]pyridine}CoCl2

The unsymmetric precursor ethyl 6-acetylpyridine-2-carboxylate （4） was synthesized from 2,6-dimethylpyridine （1）. On the basis of this precursor, a new mono（imino）pyridine ligand （5） and the corresponding Co（Ⅱ） complex {2-carbethoxy-6-[1-[（2,6-diethylphenyl）imino]ethyl]pyridine}CoCl2 （6） were prepared. The crystal structure of complex indicates that the 2-carbethoxy-6-iminopyridine is coordinated to the cobalt as a tridentate ligand using [N, N, O] atoms, and the coordination geometry of the central cobalt is a distorted trigonal bipyramid, with the pyridyl nitrogen atom and the two chlorine atoms forming the equatorial plane. Being applied to the ethylene oligomedzation, this cobalt complex shows catalytic activity of 1.820× 10^4 g/mol-Cooh at 101325 Pa of ethylene at 15.5℃ for 1 h, when 1000 equiv, of methylaluminoxane （MAO） is employed as the cocatalyst.     

斯蒂芬酸氢铷的制备，晶体结构和热分解机理

A new compound,[RbHTNR]_∞[HTNR:C_6H(NO_2)_3(OH)O],was synthesized by the reaction of rubidium ni-trate and styphnic acid.The molecular structure was characterized using X-ray diffraction analysis,elementalanalysis and FTIR spectroscopy.The crystalline is monoclinic with space group P2_1/n and the empirical formulaC_6H_2N_3O_8Rb.The unit cell parameters are:a=0.4525 nm,b=1.0777 nm,c=1.9834 nm,β=90.47(2)°,V=0.96725 nm~3,Z=4,D_c=2.263 g/cm~3,Mr=329.58,F(000)=640,μ(Mo Kα)=5.165 mm~(-1).The thermal decompo-sition mechanism of the complex was studied by differential scanning calorimetry(DSC),thermogravimetry-derivative thermogravimetry(TG-DTG)and FTIR techniques.At the linear rate of 10 ℃/min,the thermaldecomposition of the complex showed three mass reducing processes between 60 and 500 ℃,and finally evolvedRbCN and some gaseous products.     

新型硅基桥连双(环戊二烯基)四羰基二铁类配合物的合成

以六甲基二硅烷为原料,经氯代、格式反应和锂化反应制得双(环戊二烯基)配体(C5H5)2MeSiSiMe2R(3a^3c),将该配体分别与五羰基铁在对二甲苯中回流反应,合成了3种新型的硅基桥连双(环戊二烯基)四羰基二铁类配合物[η^5,η^5-C5H4MeSi(SiMe2R)C5H4]Fe2(CO)2(μ-CO)2[R=p-C6H4CH3(4a),R=p-C6H4OCH3(4b),R=CH2C6H5(4c)],其结构经1H NMR,13C NMR,IR和元素分析表征。并用X-射线单晶衍射法确定了配合物4b的分子结构。结果表明:4b(CCDC:1942618)属单斜晶系,Cc空间群,晶胞参数a=18.591(3)A,b=10.3080(10)A,c=14.136(2)A,α=90°,β=117.262(6)°,γ=90°,V=2408.1(6)A^3,Z=4,F(000)=1152,Dc=1.546 g·cm^-3,μ=1.338 mm^-1,R1=0.0351,wR2=0.0754。     

1,10-邻菲咯啉-铜(Ⅱ)-L-蛋氨酸配合物的合成、表征及其分子结构

The complex [Cu(L-met)(phen)(H₂O)]NO₃·H₂O has been synthesized and investigated by elemental analysis, molar conductivity, spectroscopic and X-ray diffraction methods, where phen=1,10-phenanthroline and L-met=L-methioninate group. The complex crystallized in the monoclinic space group P2₁ with a=12.053(2)?, b=6.886(1)?, c=13.385(3)?, β=113.59(3)°, V=1018.1(3)?³, Z=2,D_c=1.598g·cm^-3, μ=1.223mm^-1, F(000)=506, R₁=0.0306, and wR₂=0.0742. The copper(Ⅱ) atom is ligated in a distorted square-pyramidal geometry by two nitrogen atoms of one phen and the amino nitrogen atom , one carboxylate oxygen atom of L-met in the base plane, and an aqua at the apical position. A one-dimensional chain configuration formed by the hydrogen-bonding and weak Cu-O (the uncoordinated carboxyl oxygen atom) coordination interactions be-tween neighboring [Cu(L-met)(phen)(H₂O)]⁺ cations. CCDC: 183368.     

Adsorptive Voltammetry of Polyelectrolyte Complex Between 11‐Ferrocenyltrimethylundecylammonium and Polyanions at Carbon Paste Electrode

For polyelectrolyte complex between cationic surfactant and polyanion, the adsorptive voltammetry at carbon paste electrode using an electroactive cationic surfactant was examined. The adsorption state of the cationic surfactant in the complexes at CPE was estimated from the half‐height width of the oxidation waves. The half‐height width for poly(styrene sulfonate) was independent of the molecular weight, and was same as that for poly(vinyl sulfate). The half‐height width for heparin was broad and different from that of the vinyl polyanions. According to the analysis by Frumkin isotherm, the interaction between cationic surfactants was attractive in heparin complex at CPE, however, in the vinyl polyanion complexes at CPE the interaction was non‐cooperative as that predicted with the Langmuir isotherm. In spite of the same adsorption state, the concentration dependency of the peak current for poly(styrene sulfonate) was quite different from that for poly(vinyl sulfate). The concentration dependence indicated the reactive property of each polyanion on the association with the cationic surfactant in aqueous solution.