2-芳基-5-[4′-(2,2,6,6-四甲基哌啶-1-氧)氨基]-1,3,4-恶二唑自旋标记化合物的合成

2,2,6,6,-四甲基哌啶-1-氧自由基是目前应用最广泛的自旋标记试剂之一,但用哌啶氮氧自由基标记1,3,4-恶二唑类杂环的研究。迄今未见报道。1,3,4-恶二唑杂环衍生物具有抗结核、     

过氧亚硝酸诱导生成硫中心自由基的荧光表征

将4-羟基-2,2,6,6-四甲基哌啶氮氧自由基用于标记9-羧基-吖啶,得到自旋标记荧光探针4-(9-吖啶酯)-2,2,6,6-四甲基哌啶氮氧自由基. 以谷胱甘肽作为蛋白质肽模型,研究了活性氧过氧亚硝酸诱导其损伤产生的硫中心自由基的荧光表征. 自旋标记荧光探针为弱荧光物质,当与硫中心自由基作用后,导致其荧光增强,从而可对硫中心自由基进行表征.     

乙烯系单体自由基聚合的阻聚效应——ⅩⅣ.4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基低聚物的合成及对丙烯酸阻聚的研究

研究了数均分子量10~3～5×10~3的聚甲基丙烯酸甲酯的制备及其在甲醇镁存在下和2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基(TMHPO·)间的酯交换反应,合成了聚-4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基(PMTMPO·)低聚物。同时观察了4-甲基丙烯酰氧基2,2,6,6-四甲基哌啶的调聚反应,同样制得PMTMPO·低聚物。利用IR、EPR和TGA技术对PMTMPO·进行了表征。评价了PMTMPO·对AIBN引发的丙烯酸(AA)自由基聚合的影响,表明PMTMPO·对AA有良好的阻聚功效。     

2-芳基-5-[4''-(2,2,6,6,-四甲基哌啶-1-氧)氨基]-1,3,4-恶二唑自旋标记化合物的合成

本文报道了2-芳基-5-[4'-(2,2,6,6-四甲基哌啶-1-氧)氨基]-1,3,4-恶二唑自旋标记化合物的合成及其结构特征。     

乙烯系单体自由基聚合的阻聚效应——ⅩⅣ.4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基低聚物的合成及对丙烯酸阻聚的研究

 研究了数均分子量10³～5×10³的聚甲基丙烯酸甲酯的制备及其在甲醇镁存在下和2,2,6,6-四甲基-4-羟基哌啶-1-氧自由基(TMHPO·)间的酯交换反应,合成了聚-4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶-1-氧自由基(PMTMPO·)低聚物。同时观察了4-甲基丙烯酰氧基2,2,6,6-四甲基哌啶的调聚反应,同样制得PMTMPO·低聚物。利用IR、EPR和TGA技术对PMTMPO·进行了表征。评价了PMTMPO·对AIBN引发的丙烯酸(AA)自由基聚合的影响,表明PMTMPO·对AA有良好的阻聚功效。     

新型α-生育酚自旋标记衍生物的合成

以2-硝基丙烷为原料,经溴化、取代及还原反应合成了中间体2,3-二甲基-2,3-二羟胺基丁烷(3);α-生育酚与4-甲酰苯甲酸经酯化反应制得4-甲酰苯甲酸-2,5,7,8-四甲基-2-(4,8,12-三甲基十三烷基)-6-色满酯(4);3与4的加成反应产物经高碘酸钠氧化合成了一种新型的α-生育酚自旋标记衍生物——4-[2-(4,4,5,5-四甲基-1,3-二氧基-2-吡咯啉基)]苯甲酸-2,5,7,8-四甲基-2-(4,8,12-三甲基十三烷基)-6-色满酯,其结构经1H NMR,IR,HR-ESI-MS,元素分析和EPR表征。     

具有抗癌活性氟尿嘧啶自旋标记衍生物的合成

氟尿嘧啶(5-FU,1)及其一些衍生物(如FT和HCFU等)是临床上广泛使用的抗代谢类抗癌药物,但它们均具有较大的毒副作用.近年来的研究发现,一些稳定的氮氧自由基能迅速穿越细胞膜和血-脑屏障,将其作为载体与某些已知抗癌药物相连接,能显著提高药物对癌细胞的选择性~[1～5],同时也为借助电子自旋共振技术研究药物的作用机理和代谢提供了一种新手段~[4,5].为了寻找新一代高效低毒的抗癌药物和探讨氮氧自由基在标记药物中的作用机制,我们设计合成了一系列1-取代及1,3-二取代的氟尿嘧啶自旋标记衍生物2a～6b.合成路线如下:     

含有仲氨基团的甲基丙烯酸酯单体的原子转移自由基聚合研究

聚(4-甲基丙烯酰氧基-2,2,6,6-四甲基哌啶氮氧自由基)(PTMA)是一种具有应用前景的锂离子电池正极材料,一般通过2,2,6,6-四甲基哌啶醇-4-甲基丙烯酸酯(TMPM)的自由基聚合及进一步氧化来制备.但是TMPM的可控自由基聚合受制于其分子中的仲氨基团.通过对不同的引发剂和催化体系TMPM的原子转移自由基聚合(ATRP)进行了研究,得到了TMPM最优的ATRP聚合条件,为合成具有不同分子量或拓扑结构的自由基聚合物奠定了基础.     

N-(2,2,5,5-四甲基-3-吡咯啉-1-氧自由基)-N-(酰胺基)脲化合物的合成及抗癌活性

本文合成19个新的N-(2,2,5,5-四甲基-3-吡咯啉-1-氧自由基)-N-(酰胺基)脲化合物.研究了此类化合物的ESR,MS及IR波谱性质.初步观察了此类化台物对白血病L7712癌细胞以及腹水型肝癌细胞的抑制作用.发现有的化合物抑制效果显著.     

2-(2-苯并咪唑基)-4,4,5,5-四甲基-3-氧化咪唑啉-1-氧基自由基的合成、晶体结构与量化计算

报道了2-(2-苯并咪唑基)-4, 4, 5, 5-四甲基-3-氧化咪唑啉-1-氧基自由基(NITBzImH)的合成和晶体结构.晶体属正交晶系Pbca空间群.a=0.87446(4), b=1.55600(8), c=2.01139(1) nm,α=β=γ=90°,Z=8,V=2.7368(2) nm³, R=0.0478,ωR=0.1101;并用密度泛函(DFT)计算了该自由基的自旋密度分布.     

A Simple Method of Synthesis of 3-Carboxy-2,2,5,5-Tetraethylpyrrolidine-1-oxyl and Preparation of Reduction-Resistant Spin Labels and Probes of Pyrrolidine Series

Stable free radicals are widely used as molecular probes and labels in various biophysical and biomedical research applications of magnetic resonance spectroscopy and imaging. Among these radicals, sterically shielded nitroxides of pyrrolidine series demonstrate the highest stability in biological systems. Here, we suggest new convenient procedure for preparation of 3-carboxy-2,2,5,5-tetraethylpyrrolidine-1-oxyl, a reduction-resistant analog of widely used carboxy-Proxyl, from cheap commercially available reagents with the yield exceeding the most optimistic literature data. Several new spin labels and probes of 2,2,5,5-tetraethylpyrrolidine-1-oxyl series were prepared and reduction of these radicals in ascorbate solutions, mice blood and tissue homogenates was studied.     

Nitroxydes-88 : Etude de la conformation par R.P.E. d'un biradical

Dispiro(2,2,6,6-tetramethyl piperidine piperidine 1-oxy)-4,4'(oxazolidine 3'-oxyl)-2',1'-cydobexane] has been studied by ESR and NMR. Detailed analysis of the ESR spectrum of the frozen solution shows that the C-N bond of oxazolidine ring is equatorial relative to the chair piperidiae ring. Landé (g), dipolar (D) and hyperfine (A) tensors have been determined. Proton hyperfine splittings of cyclohexane ring have been measured by NMR at room temperature, with the results consistent with the C-N bond of oxazolidine ring being in equatorial position relative to the chair cyclobexane ring.     

Synthesis of the tetraethyl substituted pH-sensitive nitroxides of imidazole series with enhanced stability towards reduction

The synthesis of 2,2,5,5-tetraethylimidazole nitroxides from 3-ethylpent-2-ene is described. The newly synthesized nitroxides, namely 4-methyl-2,2,5,5-tetraethyl-2,5-dihydro-1H-imidazol-1-yloxy (1), 3,4-dimethyl-2,2,5,5-tetraethylperhydroimidazol-1-yloxy (2) and 2,2,5,5-tetraethyl-4-pyrrolidin-1-yl-2,5-dihydro-1H-imidazol-1-oxyl (3), were found to be pH sensitive spin probes, with pK values of 1.2, 4.95 and 7.4, respectively. The most important finding was the fact that these new nitroxides were 20-30 times more stable in the presence of ascorbate and had significantly longer halflifes in rat blood as compared to 2,2,5,5-tetramethyl analogs. The latter observation provides a unique advantage for the application of tetraethyl substituted imidazole nitroxides as functional EPR probes.     

3-芳基-4-[4′(2,2,6,6-四甲基哌啶-1-氧)]-1,2,4-三唑啉-5-硫酮类的合成

前文指出,各种1,4-二取代的酰氨基硫脲可在碱性物质催化下脱水环化形成1,2,4-三唑啉-5-硫酮类杂环化合物,然而连接2,2,6,6-四甲基哌啶-1-氧自由基的酰氨基硫脲类化合物能否在相同条件下环化脱水形成类似结构的杂环化合物,迄今未见文献报道。各种3,4-二取代的1,2,4-三唑啉-5-硫酮杂环化合物具有广泛的生物活性,如抗菌,杀虫等,而2,2,6,6-四甲基哌啶-1-     

ESR spin probes in ionic liquids.

The spin probes 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO), 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL), and 2,2,6,6-tetramethyl-4-trimethylammoniumpiperidine-1-oxylIodide (CAT-1) are examined in a number of ionic liquids based on substituted imidazolium cations and tetrafluoroborate and hexafluorophosphate anions, respectively. The reorientation correlation times tau(R) of the spin probes in these systems have been determined by complete spectra simulation and, for rapid reortientation, by analysis of the intensities of the hyperfine lines of the electron spin resonance (ESR) spectra. A comparison of the results with those from the model system glycerol/water and selected organic solvents is made. Additions of diamagnetic and paramagnetic ions allow the conclusion that salt effects and spin exchange are present, and that both are superimposed by motional effects. Specific interactions in the ionic liquids, as well as between the spin-probe molecules and the constituents of the ionic liquids are reflected in the spectra of the spin probes, depending on their molecular structure.     

Détermination des Axes Propres et des Valeurs Principales du Tenseur ḡ dans deux Radicaux Libres Nitroxydes par Étude de Monocristaux

The low temperature phase structure of the nitroxide radical 2,2,6,6-tetramethyl piperidin-1-oxyl (Tanane) is isomorphic of 2,2,6,6-tetramethyl-4-piperidinol-1-oxyl (Tanol). An ESR study of single crystals yielded the principal values and position of principal axes of the ? tensor in these two radicals. The major significant differences observed in Tanol are a moderate decrease in the g_xx, g_yy and g_zz values, and a deviation of the principal axes situated in the molecular mirror plane from the N? O bond and π-orbital, respectively (8° ± 2°). The intermolecular hydrogen bond is probably responsible for this fact.     

Electron spin resonance studies on the oxidation mechanism of sterically hindered cyclic amines in TiO2 photocatalytic systems

A sterically hindered cyclic amine, 4-hydroxy-2,2,6,6-tetramethylpiperidine (HTMP), is converted to the corresponding aminoxyl radical (nitroxide radical), 4-hydroxy-2,2,6,6-tetramethyl piperidine 1-oxyl (TEMPOL radical) as a result of a photocatalytic reaction in TiO2 aqueous suspension. The time profile of the radical formation and the effect of additives, such as SCN-, I-, methanol, and H2O2, on the initial formation rate were measured in order to elucidate the reaction mechanism. The experimental observations indicated that the direct photocatalytic oxidation of HTMP followed by reaction with O2 is the dominant process in the formation of TEMPOL radicals. Electrochemical measurements showed that HTMP is oxidized at 0.7 V (vs NHE), which is consistent with the proposed mechanism. The possibility of other processes, involving reactions with singlet molecular oxygen, superoxide radical, and hydroxyl radical, were excluded from the reaction mechanism.     

XPS spectra of free nitroxyl radicals and their electronic structure

The N(1s) and O(1s) XPS spectra of stable nitroxyl radicals and molecules with a related heterocycle structure: 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(3-nitrophenyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(2-hydroxyphenyl)-4,5-dihydro-1H-imidazole-3-oxide-1-oxyl, 4,4,5,5-tetramethyl-2-(2-hydroxy-3-nitrophenyl)-4,5-dihydro-1Himidazole-3-oxide-1-oxyl, and 4,4,5,5-tetramethyl-2-phenyl-4,5-dihydro-1H-imidazole-3-oxide were studied. The possibility to apply X-ray electron spectra for investigation of the charge electron and spin density distribution on free radical atoms and at their coordination by a metal is considered.     

Nanoemulsion drug delivery by ketene based polyester synthesized using electron rich carbon/silica composite surface

A new carrier matrix for nanoemulsion drug delivery was synthesized from glycine as the raw material, using mesoporous/microporous electron rich carbon-silica composite surface (MAC(800)). MAC(800) was prepared from rice husk in two-stage carbonization. The surface area, pore volume, and pore size distribution of MAC(800) were measured, using nitrogen adsorption isotherms at 77K. The unpaired electron density of MAC(800) was measured in electron spin resonance spectroscopy (ESR), using TEMPOL (4-hydroxy-2,2,6,6-tetramethyl piperidine-1-oxyl) as the reference spin probe. Glycine was converted into ketene at the surface of MAC(800), which further underwent radical polymerization to form a low molecular weight ketene polymer (LMKP) of ester structure. The structure and the properties of LMKP were confirmed through (13)C, (1)H and DEPT nuclear magnetic resonance (NMR) spectroscopy, attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and size exclusion chromatography (SEC). The two hydrophilic drugs namely ciprofloxacin hydrochloride (CPH) and gentamicin sulphate (GS) were chosen for the nanoemulsion preparation and characterization. They were characterized for morphology, interaction of drugs with the polymer and their crystallinity, using HR-TEM, DSC and XRD, respectively. The encapsulation efficiency of the LMKP towards the drugs ciprofloxacin hydrochloride and gentamicin sulphate were 26% and 12%, respectively. The dissolution studies of the nanoemulsion were carried out for the pH 6.5, 7.4 and 8.0. The cytocompatibility studies were done for LMKP as well as nanoemulsion using Hep2 epithelial cells.