用改进的羟甲基化-还原法制备d-α-生育酚

介绍了用改进的羟甲基化-还原法制备d -α-生育酚的试验结果。经优化后得到的工艺条件为(原料2 0g) :第一、第二阶段反应时间分别为70min、90min ,多聚甲醛用量分别为10 0 g、14 0g ,催化剂用量为原料重的7 0 %、反应温度同取2 0 0℃、反应氢的压力同取4 5MPa、醋酸用量1 4mL。试验结果为:α-生育酚含量95 5 1%、VE 得率91 0 8% ,经制备后的α-生育酚通过理化性质检测确认结构与天然d -α-生育酚相同。

磺酸型MCM-41非均相催化剂应用于非α-生育酚转型反应研究

针对传统的非α-生育酚均相催化转型工艺存在的催化剂残留、废液处理难度大等问题,采用两步后合成磺化法制备了嫁接磺酸基团的MCM-41非均相催化剂,并通过XRD、FTIR等方法对其进行了表征。首次将磺酸型MCM-41催化剂用于非α-生育酚的羟甲基化-加氢还原转型反应,得到适宜的转型反应条件为反应温度180℃、反应时间4.5 h、催化剂用量为天然混合生育酚原料的16%,在此条件下α-生育酚收率为77.56%。催化剂复用5次后仍然具有较高的活性,α-生育酚收率为66.27%。

用羟甲基化-还原法制备高d-α-生育酚

VE是由α、β、γ、δ-生育酚及α、β、γ、δ-三烯生育酚等8种化合物组成的混合物,它们的生理活性各异,天然的d-α-生育酚具有迄今所知的最大的VE活性。目前,d-α-生育酚生产主要还是化学转化(通常称为半合成法)。介绍用羟甲基化-还原法制备d-α-生育酚的试验结果,优化后得到优化的工艺条件为(原料20g):反应温度200℃、多聚甲醛用量为14g、催化剂钯的用量为原料重7%、反应时间6h、醋酸用量为1.4mL。实验结果为:α-生育酚含量90.62%、VE得率为91.68%,经制备后的α-生育酚通过理化性质检测确认结构与天然d-α-生育酚相同。

测序级胰蛋白酶的制备工艺与质量检测

目的:制备高纯度、酶解效率高、酶切位点专一的测序级胰蛋白酶,应用于蛋白组学研究的蛋白质鉴定与分析中。方法:取实验室自制的猪胰蛋白酶粗酶,经硼氢化钠、甲醛还原甲基化修饰抑制胰蛋白酶自水解,采用高效液相色谱仪15RPC反相柱纯化,收集对应的甲基化胰蛋白酶峰组分,冷冻干燥;甲基化修饰的胰蛋白酶进一步经甲苯磺酰苯丙氨酰氯甲酮(TPCK)修饰,以抑制糜蛋白酶等非特异性酶切活性,并经反相色谱柱再纯化,获得终产物即质谱测序级胰蛋白酶;自制的测序级胰蛋白酶经SDS-PAGE、HPLC反相色谱分析、酶比活力测定,并应用于胶内蛋白质酶切质谱鉴定氨基酸序列等,检测其纯度、酶水解效率及酶切位点特异性。结果:自制甲基化TPCK修饰的测序级胰蛋白酶纯度大于95%,酶比活力为200 U/mgP(TAME)以上,质谱分析酶切特异性好;且酶的制备工艺流程稳定,可应用于测序级胰蛋白酶产品的生产与开发中。结论:制备的测序级胰蛋白酶纯度高、酶解效率优、酶切特异性强,可广泛应用于实验室中蛋白质和肽段测序鉴定、HPLC肽段谱图分析等蛋白组学研究分析中。

高活性α-生育酚的制备

介绍了用羟甲基化—还原法制备d-α-生育酚的试验结果,并讨论了各实验因素对实验结果的影响。经优化后得到优化的工艺条件为(原料30g):反应温度200℃,多聚甲醛用量为14g,催化剂钯的用量为原料重的7%,反应时间6h,醋酸用量为1.4mL。实验结果为:d-α-生育酚含量90.62%、VE得率为91.68%,经制备后的d-α-生育酚通过理化性质检测确认结构与天然d-α-生育酚相同。

Folate levels in mucosal tissue but not methylenetetrahydrofolate reductase polymorphisms are associated with gastric carcinogenesis

AIM: To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation. METHODS: Real-time PCR was used to study the expression of tumor related genes in 76 mucosal tissue samples from 38 patients with gastric cancer. Samples from the gastroscopic biopsy tissues of 34 patients with chronic superficial gastritis (CSG) were used as controls. Folate concentrations in these tissues were detected by the FOL ACS: 180 automated chemiluminescence system. MTHFR polymorphisms were analyzed by PCR-RFLP, and the promoter methylation of tumor-related genes was determined by methylation-specific PCR (MSP). RESULTS: Folate concentrations were significantly higher in CSG than in cancerous tissues. Decreased expression and methylation of c-myc accompanied higher folate concentrations. Promoter hypermethylation and loss of p16INK4A in samples with MTHFR 677CC were more frequent than in samples with the 677TT or 677CT genotype. And the promoter hypermethylation and loss of p21WAF1 in samples with MTHFR 677CT were more frequent than when 677CC or 677TT was present. The 677CT genotype showed a non-significant higher risk for gastric cancer as compared with the 677CC genotype. CONCLUSION: Lower folate levels in gastric mucosal tissue may confer a higher risk of gastric carcinogenesisthrough hypomethylation and overexpression of c-myc.

Ni-mediated Liquid Phase Reduction of Carbonyl Compounds in the Presence of Atmospheric Hydrogen

An efficient reduction system of benzaldehyde with hydrogen under ambient pressure was developed using facile NiO catalyst. The non-aromatic solvents such as cyclohexane, tetrahydrofuran (THF) and n-hexane, and the addi-tive with strong basicity e.g. KOH, were necessary for smooth conversion of the substrate. That the catalyst can be recov-ered and reused for nine times without loss of catalytic activity indicates that this catalyst is a recyclable one for benzal-dehyde reduction.

One-pot synthesis of poly vinyl alcohol(PVA) supported silver nanoparticles and its efficiency in catalytic reduction of methylene blue

Stable silver nanoparticles were synthesized using polyvinyl alcohol （PVA） as reducing and capping agent. The method of steric stabilization was adopted for the incorporation of silver nanoparticles in the polymer matrix. The successful incorporation of silver nanoparticles in a PVA matrix was confirmed by UV–Visible spectroscopy, transmission electron microscopy （TEM） and Fourier transform infrared （FT-IR） spectroscopy. The synthesized silver nanoparticles were characterized by a peak at 426 nm in the UV–Vis spectrum. TEM studies showed the formation of spherical shaped silver nanoparticles of 10-13 nm, following the reduction by UV irradiation. Catalytic properties were studied by means of UV-Visible spectroscopic analysis. The synthesized silver nanoparticles exhibited good catalytic properties in the reduction of methylene blue.

Industrial Synthesis of N-Methylhydroxylamine Hydrochloride by Electrochemical Reduction of Nitromethane

An industrial electrolytic cell was designed for the electrochemical synthesis of N-methylhydroxylamine hydrochloride （N-MHA）. Copper was used as the cathode, graphite as the anode, and a cation membrane as the separator. The results show that N-MHA with a high purity of 99% can be electrosynthesized directly from nitromethane in HC1 solution. Under a constant current of 1000-2500A.m^-2 in the temperature of 30-50℃, the average yield, current efficiency, and reaction selectivity were 65%, 70%, and 99%, respectively. Graphite electrode and membrane material can be used continuously in the preparative electrolysis for 5000h. Moreover, the effects of the electrode and membrane materials, current intensity, electrolyte temperature, and other associated parameters on the electrosynthesis results were investigated. The direct current power consumption was 8151.3kW-h-（1000kg N-MHA）^ -1. This method is a simple separation process with limited contamination and hence, is a new green synthesis method for the industrial production of N-MHA.

Mixed hetero-/homogeneous TiO_(2)/N-hydroxyimide photocatalysis in visible-light-induced controllable benzylic oxidation by molecular oxygen

Homogeneous and heterogeneous types of catalysis are frequently considered as separate disciplines or even opposed to each other.In the present work,a new type of mixed het-ero-/homogeneous catalysis was demonstrated for the case of selective alkylarene oxidation by molecular oxygen.The proposed catalytic system consists of two widely available components:N-hydroxyphthalimide(NHPI,a homogeneous organocatalyst for free-radical chain reactions)and nanosized TiO_(2)(heterogeneous UV-active photoredox catalyst).The interaction of NHPI with TiO_(2) allows for a shift from UV to visible light photoredox activity and generation of phthalimide-N-oxyl(PINO)radicals that diffuse into the solution where NHPI/PINO-catalyzed free-radical chain reaction can proceed without the additional light input providing a fundamental increase in energy efficiency.The NHPI/TiO_(2) ratio controls the selectivity of oxidation affording preferential formation of hydroperoxide or ketone from alkylarene.

Asymmetric Synthesis of (-)-1-Trimethylsilyl-ethanol with Immobilized Saccharomyces Cerevisiae Cells in Water/Organic Solvent Diphasic System

Asymmetric synthesis of (-)-1-trimethylsilyl-ethanol with immobilized Saccharomyces cerevisiae cells in water/organic solvent biphasic system was studied. The effects of shake speed, hydrophobicity of organic solvent, volume ratio of water phase to organic phase, pH value of aqueous phase and reaction temperature on the initial reaction rate, maximum yield and enantiomeric excess (ee) of the product were systematically explored. All the above-mentioned factors had significant influence on the reaction. n-Hexane was found to be the best organic solvent for the reaction. The optimum shake speed, volume ratio of water phase to organic phase, pH value and reaction temperature were 150 r.min-1, 1/2, 8 and 30 ℃ respectively, under which the maximum yield and enantiomeric excess of the product were as high as 96.8% and 95.7%, which are 15% and 16% higher than those of the corresponding reaction performed in aqueous phase. To our best knowledge, this is the most satisfactory result obtained.

新的滇桂艾纳香寡糖BROS结构分析

以滇桂艾纳香枝叶为原料,经陶瓷膜、有机膜分离,醇沉、Sevag法除蛋白,DEAE-纤维素柱层析和SephadexG-10,SephadexG-50凝胶柱色谱纯化得到的BROS;经HPGPC检测分析表明,BROS为均一寡糖,MALDI-TOF-MS测定分子量为1314.用IR,HPLC,甲基化分析,GC-MS,NMR(1H NMR,13C NMR,1H-1HCOSY,HMQC和HMBC)等方法对BROS结构进行表征,结果表明,该寡糖由1个葡萄糖(α-D-Glcp)和7个果糖(β-D-Fruf)组成,残基间以→2)Fruf-(1→链接,分子末端链接为α-Glcp-(1→,→2)-β-D-Fruf,推出BROS的结构式为:β-D-Fruf1-(2→1)-β-D-Fruf2-(2→1)-β-D-Fruf3-(2→1)-β-D-Fruf4-(2→1)-β-D-Fruf5-(2→1)-β-D-Fruf6-(2→1)-β-D-Fruf7-(2→1)-α-D-Glcp.

Redox potentials of trifluoromethyl-containing compounds

Trifluoromethylation reactions are important transformations in the research and development of drugs, agrochemicals and functional materials. An oxidation/reduction process of trifluoromethyl-containing compounds is thought to be involved in many recently tested catalytic trifluoromethylation reactions. To provide helpful physical chemical data for mechanistic studies on trifluoromethylation reactions, the redox potentials of a variety of trifluoromethyl-containing compounds and trifluoro- methylated radicals were studied by quantum-chemical methods. First, eoB97X-D was found to be a reliable method in predicting the ionization potentials, electron affinities, bond dissociation enthalpies and redox potentials of trifluoromethylcontaining compounds. One-electron absolute redox potentials of 79 trifluoromethyl substrates and 107 trifluoromethylated radicals in acetonitrile were then calculated with this method. The theoretical results were found to be helpful for interpreting experimental observations such as the relative reaction efficiency of different trifluoromethylation reagents. Finally, the bond dissociation free energies （BDFE） of various compounds were found to have a good linear relationship with the related bond dissociation enthalpies （BDE）. Based on this observation, a convenient method was proposed to predict one-electron redox potentials of neutral molecules.

The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of(+)-preussin by step-economical methods

The first enantioselective total synthesis of(+)-preussin B and an improved synthesis of the antifungal alkaloid(+)-preussin are described. Our approach relied on the four step-economical synthetic methods developed in our laboratory:(1) the cis-diastereoselective reductive dehydroxylation of hemiaminals;(2) the direct amide/lactam reductive alkylation;(3) the one-pot N,O-bisdebenzylation-N-methylation; and(4) the one-step synthesis of malimide from malic acid. Both total syntheses are quite concise, which have been achieved in six steps, and gave overall yields of 25.7% and 27.6%, respectively.

Direct electroreduction of solid cuprous chloride to copper powder in 1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid

Direct electroreduction of solid cuprous chloride to prepare copper powder in a"neutral"ambient-temperature ionic liquid,1-butyl-3-methylimidazolium tetrafluoroborate ionic liquid(BMIMBF4)was investigated.Cyclic voltammetry of the CuCl powder in a Pt-powder cavity microelectrode exhibited that solid CuCl can be electrochemical reduced in the ionic liquid.Chronoamperometry of the salt powder filled Mo-cavity electrode(current collector)in the ionic liquid further demonstrated the conversion of chloride to metal inside the cavity,as confirmed by scanning electron microscopy,energy-dispersive X-ray,and X-ray diffraction spectra.

Synthesis and electrochemical properties of a series of novel tetra(4-benzoyl)phenoxyphthalocyanine derivatives

A novel phthalocyanine, 2,9（10）,16（17）,23（24）-tetra（4-benzoyl）phenoxyphthalocyanine, and its complexes with Zn（Ⅱ）, Cu（Ⅱ）, Co（Ⅱ）, and Ni（Ⅱ） have been synthesized and characterized by a combination of elemental analysis, IR, IH NMR, UV-vis spectroscopy and mass spectrometry. All of the materials are very soluble in common organic solvents such as dichloro- methane, chloroform, tetrahydrofuran, N,N-dimethylformamide and dimethyl sulfoxide. The Q band wavelengths of the com- plexes decrease in the order： Zn 〉 Cu 〉 Ni 〉 Co. Redox processes were observed at -1.06, -0.74, 0.51 and 0.98 V for the free phthalocyanine, at -0.72 and 1.04 V for the Co（Ⅱ） complex, at -1.24, -0.77, -0.24, 0.61 and 0,91 V for the Cu（Ⅱ） complex, and at -0.74 and 1.20 V for the Ni（Ⅱ） complex. The cyclic voltammograms of the phthalocyanine ring of the four species are similar, with reduction and oxidation couples each involving a one-electron transfer process.