硒化合物对羟基自由基作用的研究

本文选用硒代蛋氨酸(Se-Met)和无机硒化合物,采用自旋捕集技术,在温和条件下进行硒化合物与羟基自由基作用的ESR研究。实验结果表明,硒化合物对羟基自由基具有清除作用。     

明日叶黄酮类化合物清除羟基自由基活性研究

为了研究明日叶黄酮类化合物对羟基自由基的清除作用,以明日叶（主要取叶片）为原料,用体积分数为65％乙醇提取明日叶总黄酮,测定其总黄酮含量.通过Fenton反应体系产生羟基自由基,利用明日叶提取液中的功能成分黄酮类化合物对羟基自由基的清除作用进行研究.结果表明：明日叶提取物总黄酮质量分数为10.18％,且黄酮类化合物对羟基自由基有较强清除效力,当提取物总黄酮浓度在0.1～1.0 mg/mL范围内,其与清除率呈正相关.明日叶中黄酮类化合物对羟基自由基有较强清除效力,作为天然抗氧化产品开发具有一定价值.     

芳酰基硒脲合成及其对O~2清除作用的EPR研究

芳酰基硒脲的合成试剂芳酰基异硒氰酸脂是极不稳定的化合物。通过硒氰化铅在非极性溶剂苯中同芳酰氯反应能简便、稳定和可靠地合成芳酰基异硒氰酸脂、从而与芳胺反应能合成一系列芳酰基硒脲。经EFR 研究其对超氧阴离子自由基O~2具有明显的清除作用。     

两种新型水溶性异黄酮衍生物的合成与抗氧化活性

合成了未见文献报道的水溶性的3'-磺酸钠-4',7-二羧甲氧基异黄酮(L1)和3'-磺酸钠-4'-羟基-7-羧甲氧基异黄酮(L2), 采用IR, UV, ¹H NMR和元素分析对其结构进行了表征, 利用荧光光谱法研究了它们和母体大豆甙元(D)对羟基自由基的清除活性, 用紫外光谱法研究了其对超氧阴离子自由基和1,1-二苯基-2-苦肼基自由基(1,1-diphenyl-2-picrylhydrazyl free radical, 简称DPPH)的清除活性; 并采用量子化学AM1方法在全几何构型优化的基础上进行了电荷布居分析, 计算了它们抽氢反应的生成热(∆H_f), 从而从理论上探讨了目标化合物清除羟基自由基的活性. 实验结果表明本文合成的两种水溶性化合物清除超氧阴离子自由基和DPPH自由基的活性要优于母体大豆甙元, 对于目标化合物清除羟基自由基的活性, 实验和理论结果都显示其清除活性要优于大豆甙元．     

硒化合物与脂质过氧自由基作用的研究

本文以卵磷脂、亚油酸和脂质体作为生物膜模型, 鼠红细胞膜作为生物膜实例, 通过ESR研究, 观察到包括RSe和RSeSeR在内的硒化合物在模拟的和真实的生物膜体系中对脂质过氧自由基的清除作用, 使得硒作为自由基清除剂的假说在体外模型体系实验中被初步证实, 提示占体内总硒量约2/3的非GSH-Px硒可能是通过直接清除过氧自由基而发挥其生理功能, 研究表明, 其清除作用是针对生物膜磷脂分子上的不饱和脂肪酸过氧自由基, 其作用部位处于膜磷脂双分子层中部疏水区(脂相)中, 在体外实验的清除效果上, 有机硒优于无机硒, 某些有机硒化合物表面出“奇偶规律"。CNDO/2计算表明, 硒化合物清除脂质过氧自由基可能是通过硒中心自由基而起作用的。     

三种含硒环糊精的SeGPX活力及对HO·的清除作用

报道了３种硒代β－环糊精作为ＳｅＧＰＸ模拟物的活力,并初步探讨了硒环糊精的结构与活力的关系。利用Ｆｅｎｔｏｎ反应产生的羟基自由基与苯甲酸钠反应生成的具有荧光的羟基苯甲酸间接测定羟基自由基的含量。结果表明,３种含硒环糊精对ＨＯ·的生成均无明显的抑制作用。     

荧光-噻唑蓝法检测红色纳米硒的抗氧化活性

采用荧光法检测红色纳米硒的抗氧化性,并结合噻唑蓝法(MTT法)研究红色纳米硒抗氧化对细胞的作用。Fenton反应产生稳定羟自由基,罗丹明B为荧光指示剂,磷酸盐缓冲液中检测了纳米硒清除羟自由基的效果。再将纳米硒与肝细胞QSG7701共培养,检测了不同时期培养基的氧化还原状况,并用MTT实验检测作用后细胞生长情况。结果显示:纳米硒具有良好抗氧化作用,能有效改善培养基中的氧化还原环境,同时促进了细胞生长。     

七种天然黄酮类化合物对超氧阴离子自由基的清除活性

用单扫描示波极谱法研究了从东紫苏和黑沙蒿中分离出的七种黄酮类化合物对超氧阴离子自由基的清除作用.结果表明:七种黄酮类化合物清除O 2的作用强弱与它们所含酚羟基数目多少有关,羟基数目越多,对O 2清除的效果越好.C2-C3双键对黄酮类化合物清除O 2的活性也有贡献;糖苷因空间位阻效应而导致黄酮类化合物抗氧化能力下降.     

毛细管电泳法测定过氧化氢酶与天然抗氧化剂协同清除羟自由基作用

在抗坏血酸/Fe2+羟自由基产生体系中,以苯甲酸为羟自由基捕获剂,建立了羟自由基的毛细管电泳分析方法。优化了背景缓冲液的pH值、电解质浓度、表面活性剂浓度及分离电压。在最优的电泳条件下,研究了羟自由基产生体系中各底物浓度和反应时间对产物生成量的影响。本方法可在15 min内实现体系中的各物质的分离;产物间羟基苯甲酸的线性范围是5×10!6~1×10!3mol/L,检出限为2.8×10!7mol/L。将本方法用于血清基质中过氧化氢酶、原花青素和绿原酸对羟自由基IC50的测定,并研究了过氧化氢酶与原花青素及与绿原酸的协同清除羟自由基作用。结果表明,过氧化氢酶与原花青素及与绿原酸均存在协同清除羟自由基作用,在过氧化氢酶与原花青素的协同作用间还存在量效关系。     

双峰倍增配平法用于同步、导数-同步荧光法同时测定邻羟基苯甲酸和间羟基苯甲酸

邻羟基苯甲酸（ｏＨＢＡ）和间羟基苯甲酸（ｍＨＢＡ）荧光光谱严重重叠，同步及导数技术虽使选择性有所改善，但仍不能完全分辨开重叠谱。用双峰倍增配平计算法结合同步、一阶导数－同步荧光法对双组分体系（邻羟基苯甲酸／间羟基苯甲酸，ｐＨ１２介质）同时测定。结合计算的两种测定方法精密度、回收率和不同组分间浓度比范围均优于一阶导数－同步荧光法。     

二氧化碳和丙烯直接合成甲基丙烯酸的NiPMo/TiO2催化剂的研究

用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%.     

Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction

In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments.     

CoFe2O4自形成磁性液体场致结构化对磁化的影响

The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula.     

Highly regioselective Buchwald–Hartwig amination at C-2 of 2,4-dichloropyridine enabling a novel approach to 2,4-bisanilinopyridine (BAPyd) libraries

The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines.     

KMnO4-mediated oxidative CN bond cleavage of tertiary amines: Synthesis of amides and sulfonamides

KMnO₄-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields.     

Chemistry of heterocyclic compounds at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences, over 50 years (Review)

The review contains a concise historical account and information on the most significant researches undertaken by the staff at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry of Heterocyclic Compounds. Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008.     

Sulfur-directed metal-free and regiospecific methyl C(sp3)–H imidation of thioanisoles

Regiospecific and direct imidation of the methyl C(sp³)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products.     

Selective syntheses of 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones via temperature-dependent Rh(II)-carbenoid-mediated 2H-azirine-ring expansion

The Rh(II)-catalyzed reaction of 2-carbonyl-substituted 2H-azirines with ethyl 2-cyano-2-diazoacetate or 2-diazo-3,3,3-trifluoropropionate provides an easy access to 2H-1,3-oxazines and 1H-pyrrol-3(2H)-ones. These compounds can be selectively prepared from the same starting material using temperature as the only varied parameter. The 2-azabuta-1,3-diene intermediate, a common precursor for both heterocyclic products, isomerizes into 2H-1,3-oxazine under kinetic control, while 1H-pyrrol-3(2H)-one is the sole product of the reaction at elevated temperatures. According to DFT-calculations a one-atom oxazine ring contraction involving ring-opening to a 2-azabuta-1,3-diene intermediate, followed by a 1,5- and 1,2-prototropic shift leads to the consecutive formation of imidoylketene and azomethine ylide, which then further undergo cyclization to the pyrrole derivative.     

Synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives

Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields.