含自由氨基酸侧链的温敏性微凝胶的制备及性能

采用无皂乳液聚合法使N-异丙基丙烯酰胺(NIPAM)、ε-丙烯酰基-L-赖氨酸(εACRLLY)和N,N-亚甲基双丙烯酰胺(BA)交联共聚,制备了含有自由氨基酸侧链的温敏性微凝胶.利用透射电子显微技术(TEM)、动态光散射技术(DLS)及浊度法对所制备的微凝胶的形态及相转变进行了表征.TEM结果表明,所得的微凝胶具有规则的球型形态,微凝胶的粒径随εACRLLY含量的增加而减小.DLS及浊度结果表明,微凝胶粒径呈单分散的窄分布,随着温度的升高,微凝胶粒径减小,有着明显的体积相转变温度(VPTT);亲水单体εACRLLY的引入能够有效地调节共聚物微凝胶的VPTT,并且VPTT随εACRLLY含量的增加几乎呈线性上升.微凝胶在对盐酸阿霉素的药物释放研究表明,所制备的微凝胶在20℃,12 h内释放了56%,37℃下释放了73%;37℃,pH=7.4下13 h内释放73%,pH=4.5下基本释放完毕,该微凝胶表现出良好的药物缓释性能.     

聚(4-乙酰基丙烯酰乙酸乙酯-co-丙烯酸)水凝胶的溶胀动力学以及温度敏感性研究

通过分子结构设计, 合成了疏水性单体4-乙酰基丙烯酰乙酸乙酯(AAEA), 并以该单体与丙烯酸(AA)进行自由基溶液共聚, 制备了P(AAEA-co-AA)新型温度敏感性水凝胶. AAEA的¹H NMR及FT-IR分析表明, 该单体主要以烯醇式结构存在; P(AAEA-co-AA)的FT-IR分析发现, PAAEA与PAA之间存在较强烈的氢键作用, 使得AAEA烯醇异构体中的C—O伸缩振动吸收峰移向了低波数处. 对冷冻干燥后凝胶的电镜分析发现, 当AAEA用量较高时, 由于凝胶内部分子链段的疏水聚集, 各部分溶胀度以及溶胀速度不均一而使得凝胶表面粗糙不平. 采用DSC对凝胶的体积相转变进行了研究, 结果表明, 该水凝胶的体积相转变温度(VPTT)在48.2至61.8 ℃之间, 并且随着AAEA用量的减小, 凝胶的VPTT逐渐增加. 对该新型温度敏感性水凝胶在去离子水中的溶胀动力学研究发现, 当AAEA用量高于4.6 g时, 凝胶属于Fick凝胶; 反之凝胶则属于非Fick凝胶. 该水凝胶在去离子水中具有良好的温度敏感性, 当外界温度低于VPTT时, 凝胶能保持溶胀状态; 而当外界温度高于VPTT时, 凝胶的平衡溶胀度迅速下降, 表现为温度敏感性. 进一步研究发现, 凝胶组成不仅会影响凝胶的VPTT, 而且会影响凝胶温度敏感性的强弱.     

PVA增强P(AAEA-co-AA)温度敏感性水凝胶的合成及其性能研究

以4-乙酰基丙烯酰乙酸乙酯(AAEA)、丙烯酸(AA)以及PVA为原料, 通过自由基溶液聚合法, 制备了PVA-P(AAEA-co-AA)半穿网络型(s-IPN)水凝胶. 红外分析表明, AAEA主要以烯醇式结构存在, 并且由于PAAEA, PAA以及PVA之间较强的氢键作用, 使得PAAEA以及PVA分子上的C-O伸缩振动吸收峰移向了低波数处. 电镜分析表明, PVA能贯穿于P(AAEA-co-AA)交联网络中, 从而有效阻碍凝胶的相分离|而XRD研究发现, 当PVA用量较少时, PVA能均匀的贯穿于凝胶网络中, 形成完善的互穿网络结构, 当PVA用量过高时, PVA不能有效地贯穿于聚合物交联网络中而出现结晶. 采用DSC对s-IPN水凝胶的体积相转变进行了研究, 结果表明, 该s-IPN水凝胶的体积相转变温度(VPTT)在54.0至57.8 ℃之间, 并且随着PVA用量的增加, 凝胶的VPTT逐渐升高. 研究了该s-IPN水凝胶的抗压缩性能, 结果表明, PVA与P(AAEA-co-AA)形成的半互穿网络结构能有效提高凝胶的抗压缩强度, 其最大抗压缩强度可达8.4 MPa. 对凝胶的温度敏感性研究发现, 当外界温度低于VPTT时, 凝胶能保持溶胀状态|而当温度高于VPTT时, 凝胶的平衡溶胀度迅速下降, 表现为温度敏感性.     

快速响应大孔聚(N-异丙基丙烯酰胺-co-丙烯酸)水凝胶的合成及表征

以聚乙二醇6000为成孔剂,由自由基引发N-异丙基丙烯酰胺(NIPA)和丙烯酸(AAc)共聚交联得到大孔凝胶,研究了凝胶对环境温度的响应性能.在凝胶制备过程中,PEG6000分子充当成孔剂,得到的凝胶具有大孔结构.这种大孔结构有利于水分子的进出,大孔凝胶对温度变化有较快的响应速率.增加亲水单体AAc的含量,凝胶的LCST有所升高,凝胶的亲水性增强,在较低温度下凝胶的溶胀率也随之升高.振荡实验表明,所得的大孔凝胶具有反复使用的能力.     

低共熔溶剂中酶催化水解黄芩苷的工艺条件研究

研究用低共熔混合物作为溶剂,黄芩自生酶催化水解黄芩苷的工艺条件。以黄芩苷的水解率为指标,采用单因素试验和正交试验,考察了温度、底物浓度和加酶量等因素,采用HPLC法测定黄芩苷的含量。选择了含水量80%的ChCl∶U=1∶1的低共熔溶剂作为溶解黄芩苷的溶剂,确定最优水解工艺条件为反应温度为50℃,黄芩苷浓度为0.2 mg·mL~(-1),加入黄芩自生酶160μL·mL~(-1)。以低共熔混合物作为溶剂,黄芩自生酶催化水解黄芩苷是一种绿色环保、经济、快速的方法。     

紫外分光光度法测定黄芩中黄芩苷的含量

从黄芩中提取黄芩苷,并用紫外分光光度法对纯化后的黄芩苷进行测定。建立了一种以乙醇为溶剂、超声溶解制样、检测波长为278nm的测定黄芩苷含量的新方法。纯化后黄芩苷纯度达98．76％,黄芩苷乙醇溶液的含量在1～18μg／mL之间与吸光度呈良好的线性关系,相关系数为0．9993,平均回收率为99．49％,相对标准偏差为0．328％（n=4）。该方法适用于黄芩苷的定量测定。     

黄芩苷在纳米MnO2-离子液体修饰电极上的电化学性质及电分析方法研究

用疏水性离子液体1-丁基-3-甲基咪唑六氟磷酸盐([BMIM]PF6)和纳米MnO2作修饰剂,通过壳聚糖(CHIT)的成膜效应,构置了玻碳修饰电极([BMIM]PF6-MnO2-CHIT/GCE).在Britton-Robinson(B-R)缓冲液中研究了黄芩苷在修饰电极上的电化学行为,建立了测定黄芩胶囊中黄芩苷含量的...     

葡聚糖凝胶柱层析法测定黄芩苷脂质体载药性能的研究

采用逆相蒸发法制备黄芩苷脂质体,通过葡聚糖凝胶G-50柱层析分离游离黄芩苷和黄芩苷脂质体,比较不同流速和不同上样量条件下的分离效果,考察包封率测定方法的回收率,确定黄芩苷脂质体包封率的测定方法,并对黄芩苷脂质体的制备工艺进行优化。结果表明,以PBS为洗脱液(柱直径Φ为16mm,床层高度h为18cm),当采用流速0.5mL/min进行洗脱,进样量为3mL时,黄芩苷脂质体和游离黄芩苷的分离效果最好,且该方法测定包封率的回收率较高;据方差分析可知,大豆磷脂与胆固醇质量比(m_(大豆磷脂)/m_(胆固醇))、有机相与水相体积比(V_(有机相)/V_(水相))和黄芩苷浓度均对黄芩苷包封率有显著性影响,优化条件为:m_(大豆磷脂)/m_(胆固醇)为2:1、V_(有机相)/V_(水相)为3:1、黄芩苷浓度为1.6mg/mL。该条件下,黄芩苷脂质体包封率为(81.22±1.22)%,可采用葡聚糖凝胶G-50柱层析分离测定黄芩苷脂质体的包封率。     

黄芩苷和栀子苷抗炎活性和抗炎机理的理论研究

药理实验研究表明，黄芩-栀子药对主要成分黄芩苷和栀子苷配伍可抗脑缺血炎性损伤，其作用机制可能与抑制COX-2的表达和活性有关。在此基础上，本文运用密度泛函理论和分子对接方法，以黄芩苷和栀子苷为研究对象，以环氧合酶COX-2为靶点，从分子水平上揭示黄芩苷和栀子苷的结构与抗炎活性之间的关系，探讨黄芩苷-栀子苷配伍治疗脑缺血炎性损伤的作用机制。综合研究结果可知，黄芩苷对COX-2的抑制作用大于栀子苷对COX-2的抑制作用，黄芩苷的抗炎活性强于栀子苷，从而为黄芩苷和栀子苷的抗炎活性和作用研究提供了实验基础和理论依据。     

紫外光谱法结合多元曲线分辨研究黄芩苷的转化规律

采用紫外光谱法采集不同工艺条件下黄芩苷转化过程的光谱数据, 结合多元曲线分辨-交替最小二乘法(MCR-ALS)处理获得的数据, 得到黄芩苷转化反应过程中各组分的光谱图和浓度随时间变化曲线. 结果表明, 黄芩苷转化过程符合两步连续一级反应模型; 根据不同时间点采集的多级质谱和飞行时间质谱信息, 推断了黄芩苷转化产物和可能的转化途径, 转化产物主要包括黄芩苷的同分异构体、 黄芩素和黄芩素二聚体. 对黄芩苷转化规律的研究有助于黄芩制剂的质量控制.     

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%.     

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.     

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.     

A general and convenient synthesis of 4-(tosylmethyl)semicarbazones and their use in amidoalkylation of hydrogen,heteroatom, and carbon nucleophiles

A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL.     

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.     

Synthesis of novel chiral bidentate hydroxyalkyl-N-heterocyclic carbene ligands and their application in palladium-catalyzed Mizoroki–Heck couplings and asymmetric addition of diethylzinc to benzaldehyde

A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions.