Synthetic enantiopure aziridinomitosenes: preparation, reactivity, and DNA alkylation studies

An enantiocontrolled route to aziridinomitosenes had been developed from l-serine methyl ester hydrochloride. The tetracyclic target ring system was assembled by an internal azomethine ylide cycloaddition reaction based on silver ion-assisted intramolecular oxazole alkylation and cyanide-induced ylide generation via a labile oxazoline intermediate (62 to 66). Other key steps include reductive detritylation of 26, methylation of the N-H aziridine 56, oxidation of the sensitive cyclohexenedione 68 to quinone 70, and carbamoylation using Fmoc-NCO. Although the aziridinomitosene tetracycle is sensitive, a range of protecting group manipulations and redox chemistry can be performed if suitable precautions are taken. A study of DNA alkylation by the first C-6,C-7-unsubstituted aziridinomitosene 11a has been carried out, and evidence for DNA cross-link formation involving nucleophilic addition to the quinone subunit is described.     

原子吸收光谱法间接测定叶酸的含量

在pH5．0的NaOAc-HOAc缓冲溶液中，过量的硝酸银完全沉淀叶酸，用原子吸收光谱法测定剩余的硝酸银，间接计算出叶酸的含量。方法简单快速，回收率在98％～104％之间，相对标准偏差为2．4％。     

羧甲基壳聚糖/聚乙烯醇/甘油环氧树脂蛇笼型复合螯合膜的制备及对金属离子的吸附性能

以交联甘油环氧树脂交联的聚乙烯醇(PVA)为笼树脂，羧甲基壳聚糖(CCTS)为蛇树脂制备了具有蛇笼结构的复合螯合膜，研究了其对Cu^2 、Ni^2 、Pb^2 、Fe^3 、Zn^2 ，Hg”^2 、Cd^2 等金属离子的吸附性能，研究表明，该树脂对Cu^2 、Ni^2 、Pb^2 有较好的吸附性能，其中PVA是对Cu^2 的吸附的主要贡献者，而CCTS则是在对Ni^2 的吸附中起主要作用。该树脂可以用于含Cu^2 废水的处理。     

Fluoride and lead adsorption on carbon nanotubes

The properties and applications of CNT have been studied extensively since Iijima discovered them in 1991[1,2]. They have exceptional mechanical properties and unique electrical property, highly chemical stability and large specific surface area. Thus far, they have widely potential applications in many fields. They can be used as reinforcing materials in composites[3], field emissions[4], hydrogen storage[5], nanoelectronic components[6], catalyst supports[7], adsorption material and so on.…     

Study on the Tautomer Interconversion of 3-Oxo Pentanoate During Gas Chromatography

Enol and keto tautomers of methyl 3-oxo pentanoate could be separated on a HP-5 capillary column. The chromatographic peaks were identified by examining characteristic mass ions arose from the corresponding enol and keto molecular ions. The study showed that the area percentage of enol tautomer is a function of temperature of the column. Treating the column as a reactor, the energy of activation for the on-column tautomerization could be extracted (35.1 kJ mol⁻¹) by monitoring the loss of the enol tautomer, because the reaction is found to obey pseudo first-order kinetics. The enthalpy and the entropy changes (ΔH = −3.98 kJ mol⁻¹, ΔS = −7.89 J K⁻¹mol⁻¹) for the enol-to-keto reaction in the stationary phase were also obtained.     

有机锡试剂在有机合成中的某些新应用

本文阐述有机锡试剂在有机台成巾的一些新应用。在钯催化下,有机锡试剂与亲电试剂进行偶联,条件温和,收率高。有机锡试剂促进醇醛缩合,可用于不对称合成中。     

On-line Separation and Detection of Peptides by Capillary Electrophoresis / Electrospray FT-ICR-MS

Recently, capillary electrophoresis/electrospray ionization mass spectrometry (CE/ESI- MS) has been rapidly developed as a powerful analytical tool for charged species ranged from small molecules such as carboxylic acids1, phenolic compounds2, metal species3, tetramines4, herbicides5, drugs and drug metabolites6 to peptides and proteins7, 8. The ESI mode has proven to be sensitive, versatile and relatively easy to use in combination with CE. CE confers rapid analysis and efficient separ…     

A New Approach to α—Bromochalcones

α-Bromo benzolymethylene triphenylphosphorane 3 has been synthesized by the reaction of benzoylmethylene triphenylphosphorane 1 with N-bromosuccinimide in the yield of 87% and can react with aromatic aldehydes 4 to give α-bromochalcones 5 in good yields.     

化学镀钴基合金镀液中钴的快速测定

研究了采用显色剂 苦胺酸偶氮变色酸对化学镀钴基合金镀液中钴含量进行测定的试验条件,在pH11的氨 氯化铵缓冲溶液中,钴与显色剂配合物的最大吸收峰在650nm波长处,钴(Ⅱ)在0～60μg/25ml范围内服从比耳定律,表观摩尔吸光系数为3.1×104L·mol-1·cm-1。该法测定钴的选择性好,在大量镍存在下,也能准确测定,对镀液样品进行了测定,相对标准偏差小于1%,结果满意。     

Synthesis of Cucurbit [ n ] uril-based Rotaxanes

Non-covalent attractive forces are commonly employed in biological systems to drive the assembly of highly orga nized supramolecular entities from relatively simple subunits.