毛细管区带电泳分离和测定嘧啶碱

本报道毛细管区带电泳分离和测定胞嘧啶，胸腺嘧啶，尿嘧啶，羟乙基氟尿嘧啶，尿嘧啶丙酸和５－氟尿嘧啶，在熔硅毛细管（７０ｃｍ×７５μｍｉ，ｄ，有效长度６３ｃｍ）上，以０．０１ｍｏｌ／Ｌ硼砂缓冲溶液（ｐＨ＝９．２５）作电解质，电压为２０ｋＶ，温度为３５℃，真空进样１ｓ，于２７０ｎｍ处检测，可在８ｍｉｎ内完全分离上述６种嘧啶碱，塔板数达到２．５×１０＾５，碱基检测限为（０．９～３．６）×１０＾－６ｍｏｌ     

七种嘧啶碱和嘌呤碱的胶束电动毛细管色谱分离研究

研究了影响七种核酸碱基－胸腺嘧啶，尿嘧啶，胞嘧啶，腺嘌呤，腺嘌呤，腺嘌呤、鸟嘌呤，黄嘌呤和次黄嘌呤毛细管电泳分离的因素。在２４．５℃下，七种碱基在４０ｍｍｏｌ／Ｌ十二烷基硫酸钠－１０ｍｍｏｌ／Ｌ硼砂－１７％－３．０ｍｍｏｌ／Ｌβ－环糊精缓冲液中电泳可得良好分离，保留时间的变异系数小于１．８％。     

毛细管电泳用于评价脱氧核糖核酸退火反应

将毛细管电泳技术用于定性和定量评价互补单链脱氧核糖核酸（DNA）的退火反应，从电泳信号能直接观察退火效率。解释了双链DNA的电泳迁移特性，对DNA产品基质中的NaCl浓度进行了测定，考察了DNA样品中NaCl浓度对进样的稀释效应。在所应用的实验条件下，NaCl浓度在20mmol/L以内稀释效应的影响是可以忽略的。     

毛细管离子分析的高灵敏化学发光检测

首次报道毛细管离子分析的新型研究技术─—自行组装的毛细管电泳化学发光检测器,将内径为５０μｍ的电泳毛细管经刻蚀插入内径为５３０μｍ的反应管,内径为１２０μｍ的试剂管通过聚四氟乙烯三通将试剂引入反应管中,反应管上的检测窗定位于光电倍增管前,使光信号尽可能多地被接收。金属离子催化鲁米诺－过氧化氢发光是较灵敏的化学发光研究体系,但干扰严重。高效液相色谱分离对象有限,分离效率不十分理想。本系统成功地基线分离了Ｃｏ￣（２＋）、Ｃｕ￣（２＋）、Ｎｉ￣（２＋）、Ｆｅ￣（３＋）、Ｍｎ￣（２＋）五种金属离子。     

毛细管电泳在线化学发光分离及检测铬（Ⅲ）与钒（Ⅴ）

基于在碱性介质中 Cr( )和 V( )对鲁米诺和过氧化氢的催化化学发光反应 ,研究了毛细管电泳在线化学发光分离和检测 Cr( )和 V( )。方法简便、快速、灵敏、进样量少。 Cr( )和 V( )的检出限分别为 7.8× 1 0 - 8mol/L和 5.0× 1 0 - 6mol/L ,线性范围分别是 32～ 80 ng/m L和 0 .55～ 3.0μg/m L     

毛细管电泳接触反应法测定血清中铁传递蛋白的浓度

建立了一种测定血清中铁传递蛋白的毛细管电泳接触反应方法，利用血清中铁传递蛋白计算化学结合铁的性质，用标准铁饮和铁传递蛋通过对铁准确定量，测定血清铁伟递蛋白的有浓度。     

毛细管电泳电化学检测测定阿司匹林水解反应速率常数

本文利用毛细管电泳-电化学检测方法研究了阿司匹林水解产物水杨酸的浓度随反应时间变化的规律。在pH7．4的中性条件下,在不同温度下对阿司匹林水解反应速率进行了测定,并分别求得反应活化能Ea为786．8kJ／mol。     

阿魏酸转化反应速率常数的毛细管电泳测定方法研究

初步确定了阿魏酸自然转化产物的结构 ,并用毛细管电泳测定了转化反应速率常数。在常温下 ,用毛细管区带电泳法直接测定阿魏酸浓度随时间变化的规律 ,并根据HPLC -MS -MS得到的质谱图及紫外光谱图初步确定了转化产物。在23℃ ,阿魏酸转化反应正向和逆向反应速率常数分别为5.194×10 -6s -1、5.360×10 -6s -1。方法简单、灵敏、快速     

蔗糖水解反应速率常数的毛细管电泳测定方法研究

利用具有高分辨率和高灵敏度的毛细管电泳-电化学检测方法直接测定蔗糖及其水解产物的浓度随反应时间变化的规律．在HCI催化下，对不同温度时蔗糖的水解反应速率常数进行了测定，并求得反应活化能Ea为109．8kJ／mol．该方法比经典的旋光度测定方法更直观简便，结果令人满意．     

固定化D-氨基酸氧化酶催化DL-氨基酸去消旋化制备非天然L-氨基酸

在过氧化氢酶和氧气存在下,固定化D-氨基酸氧化酶(D-AAO)对映选择性催化DL-氨基酸中的D-对映体氧化脱氨为相应酮酸,L-对映体保留.研究了D-AAO的底物特异性并对反应条件进行了优化.结果表明:D-AAO具有较宽的底物谱,能够催化疏水性α-氨基酸的D-对映体氧化脱氨.在最优反应条件下,D-AAO催化DL-2-氨基丁酸、DL-2-氨基戊酸去消旋化,L-2-氨基丁酸、L-2-氨基戊酸的收率分别为48%和47%,ee分别为99.5%和99.8%.进一步地利用Pd-C/HCOONH4催化氧化脱氨过程中产生的亚氨基酸原位还原,有效提高了L-2-氨基丁酸、L-2-氨基戊酸的收率并保持高的光学纯度.     

A carbanion induced synthesis of highly congested pyrazole and imidazole containing heterocycles

An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions.     

α-Amino acid derived enaminones and their application in the synthesis of N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates and other heterocycles

A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives.     

Specific intramolecular aromatic CH insertion of diazosulfonamides

The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp³)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp²)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp²)?H and aliphatic 1,5- and 1,6-C(sp³)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp³)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp²)?H insertion.     

Selective synthesis of 4,5-dihydroimidazo- and imidazo[1,5-a]quinoxalines via modified Pictet–Spengler reaction

An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction.     

N-Heterocyclic carbene-palladacyclic complexes: synthesis,characterization and their applications in the C-N coupling and α-arylation of ketones using aryl chlorides

N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%).     

Understanding the Diels-Alder reactivity of 1,2-azaborine analogues

The Diels-Alder reactivity of 1,2-heteroborines (H₄C₄B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed.     

Synthesis of N-substituted carbazolones from α-iodo enaminones via Pd(0)-catalyzed intramolecular coupling under microwave irradiation

A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd₂(dba)₃-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring.     

Synthesis of substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles by intramolecular nitrilimine cycloaddition

Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles.     

Iodine-mediated oxidative Pictet-Spengler reaction using terminal alkyne as the 2-oxoaldehyde surrogate for the synthesis of 1-aroyl-β-carbolines and fused-nitrogen heterocycles

An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y₁ and Y₂. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones.     

Facile synthesis of bicyclic 1-arylpyrazol-5-ones

In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates.