以七-(2,6-二-O-甲基)-β-环糊精为核磁共振手性溶解剂测定布洛芬的光学纯度

研究了七-(2,6-二-O-甲基)-β-环糊精(DM-β-CD)作为核磁共振手性溶解剂在识别布洛芬对映体及测定布洛芬光学纯度中的应用。在DM-β-CD存在下,布洛芬对映体混合物~1H-NMR谱的某些吸收峰裂分成两组信号,分别对应两个对映体,可以用于确定布洛芬的绝对构型。DM-β-CD可以使布洛芬~(13)C-NMR谱的某些核磁信号裂分成两个完全没有重叠的吸收峰,不但可以确定布洛芬的绝对构型,而且可以测定布洛芬对映体混合物的光学纯度。     

两种七元瓜环与3-(2-萘基)-丙氨酸的包结行为分析

以反式七元瓜环(i Q[7])和七元瓜环(Q[7])作为主体分子,一对氨基酸对映体L-3-(2-萘基)-丙氨酸(L-NA)及D-3-(2-萘基)-丙氨酸(D-NA)为客体分子,利用紫外-可见吸收光谱、荧光光谱、等温滴定量热分析、基质辅助激光解吸电离飞行时间质谱以及核磁共振技术等手段,对比探究了这两种具有不同空腔大小的七元瓜环与这一对氨基酸对映体之间的自组装模式的异同点,实验结果表明:这四组主客体包结物具有相同的作用模式,均为瓜环的空腔包结了客体分子的萘环部分而客体分子的氨基及羧酸部分位于瓜环的端口外侧,主客体均以1∶1的作用比相互配位形成较为稳定的超分子自组装体,同时发现两种七元瓜环对L/D-NA手性对映体的分子选择性略有不同.     

手性单Schiff碱大环对青霉胺对映体识别研究

大量手性药物分子均具有D-和L-对映异构体, 呈镜像结构的对映体通常表现出截然不同的生理学反应. 青霉胺(Pen)是从青霉素中获取的一种常见的手性药物, 研究者为了实现这两种对映异构体严格区辨和分析一直在不断付出努力. 基于含有NH功能基的手性席夫碱大环化合物具有合成条件温和、结构收敛的优点, 本工作报道了含NH功能基的手性单Schiff碱大环对映异构体的合成(C_R和C_S)及其对小分子青霉胺对映体(D-Pen和L-Pen)的键合作用及对映体识别选择性. 通过X射线单晶衍射技术解析了单Schiff碱大环对映异构体的晶体结构, 结果表明这两个大环对映体均具有扭曲的非平面构型, 环状骨架中与环己基手性碳相连的亚胺(NH)质子均指向环腔内侧. 采用紫外可见光吸收光谱(UV-Vis)和核磁共振氢谱(¹H NMR)滴定技术对手性大环与青霉胺对映体之间相互作用行为进行考察, 表明手性大环与青霉胺不同对映体键合比均为1∶1, 键合常数接近10⁷ L•mol^-1, 电喷雾电离质谱法(ESI-MS)表征观察到大环与青霉胺按1∶1键合的缔合物[C-Pen+H]⁺的分子离子峰. ¹H NMR滴定表明手性大环与青霉胺对映体之间的缔合源于大环结构中不对称NH功能基与青霉胺对映体之间形成分子间氢键作用. 通过手性大环与青霉胺对映异构体之间的键合常数比较, 表明大环C_R对L-Pen具有更高的选择性键合能力, 而C_S则对D-Pen表现出更高的选择性键合能力, 选择性键合常数比均接近2倍. 进一步通过圆二色光谱(CD)滴定考察, 阐释了手性大环与青霉胺对映体选择性键合作用能力与两者之间对映体结构的手性匹配性质密切相关, 主体大环对与其手性相匹配青霉胺对映体表现出较高的键合作用能力, 而与手性不相匹配的青霉胺对映体键合作用则相对较弱.     

化学修饰环糊精—胶束动电色谱法直接拆分巴比妥对映体

应用胶束动电色谱法，于移动相中直接加入环糊精作为手性选择剂，用于对４种手性巴比妥盐的对映体拆分。实验结果表明，十二烷基磺酸钠和γ－环糊精体系对戊巴比妥和戊硫巴比妥对映体具有手性识别作用，这两种巴比妥盐的手性碳位于脂肪侧链上，与巴比妥环相隔一碳原子；胆酸和α－环糊精体系可直接拆分这四对手性对映体。本文还讨论了胆酸、ＳＤＳ对环糊精的手性识别作用的影响以及经甲基化修饰的环糊精的手性识别作用的变化。     

石墨烯基环糊精传感器的构建及对组氨酸对映体的电位识别

以具备手性识别作用的环糊精聚合物为手性选择剂, 以石墨烯为手性放大材料, 通过层层修饰的方法构建了石墨烯基环糊精聚合膜电位识别传感器. 由所构建的传感器测得的组氨酸对映体的氧化峰电位存在明显的差异, 电位差值近100 mV, 且不同比例的组氨酸对映体混合溶液的氧化峰电位值与对映体过量值呈现良好的线性关系. 据此, 建立了一种通过电位同时识别组氨酸对映体两组分的新方法.     

大环抗生素手性固定相拆分克伦普罗对映体及分离机制研究

应用三种大环抗生素类手性固定相Chirobiotic V、Chirobiotic T和Chirobiotic R,采用高效液相色谱法对盐酸克伦普罗对映体进行了拆分研究。实验考察了洗脱模式、流动相组成、柱温等因素对分离的影响,对分离结果进行了比较,并对其分离机制进行了探讨。结果表明,盐酸克伦普罗对映体在Chirobiotic R手性固定相上不能实现分离,在Chirobiotic V和Chirobiotic T手性固定相上,最佳色谱条件为:新极性有机相模式,流动相为甲醇-乙酸-三乙胺(100∶0.01∶0.01,V/V/V),流速:1.0mL/min,柱温:20℃,分离度可分别达到2.00和2.13。实验证明,盐酸克伦普罗对映体与大环抗生素类固定相之间的离子相互作用是实现对映体分离的最主要分离机制。     

手性金属有机骨架构筑的电化学传感器对色氨酸对映体的识别

本文将金属离子(Cu(Ⅱ)), 1,10-菲啰啉(Phen)和L-谷氨酸(L-Glu)组装,使用一锅法合成了手性金属有机骨架(L-Glu-Phen-Cu(Ⅱ))。L-Glu-Phen-Cu(Ⅱ)作为一种新型的电化学传感界面,由于具有良好的对映体选择性(IL/ID=2.24),被用于对色氨酸(Trp)对映体的手性识别中。Cu(Ⅱ)和L-Glu配位实现了L-Glu-Phen-Cu(Ⅱ)立体选择性的构建,Cu(Ⅱ)和Phen配位增强了电化学信号,实现了L-Glu-Phen-Cu(Ⅱ)高对映选择性的构建。本研究不仅为高效的Trp对映体检测提供了一种易于调节、低成本的传感界面,而且将直接合成的手性MOFs用于手性识别提供了一种可行的新思路。     

3，5-二甲基苯基异氰酸酯替考拉宁和苯基异氰酸酯替考拉宁手性固定相的评价与比较

用大环抗生素替考拉宁手性固定相(TE CSP)分别与3,5-二甲基苯基异氰酸酯和苯基异氰酸酯反应得到了两种新型的高效液相色谱手性固定相----3,5-二甲基苯基异氰酸酯替考拉宁手性固定相(DMP-TE CSP)和苯基异氰酸酯替考拉宁手性固定相(Ph-TE CSP)。用十八个手性化合物在反相及极性流动相模式对这两种CSP的对映体分离能力进行了评价和比较。在反相流动相中,十二个化合物（包括八个氨基酸和四个非氨基酸化合物----对羟基苯甘氨酸,拉米夫定,醇酸和去甲羟安定）的对映体在这两种手性固定相上都获得了分离,大部分的溶质在DMP-TE上获得了更强的保留和稍好的手性分离效果。在极性流动相中,六个氨基醇类化合物在DMP-TE上获得了更强的保留,但它们在两种CSP上的选择因子几乎没有区别。对自制的替考拉宁衍生物手性固定相进行评价和比较,将有助于大环糖肽类抗生素手性固定相手性识别机理的研究。     

高效液相色谱手性流动相添加剂法拆分酪氨酸甲酯对映体

分别将β-环糊精、羟丙基-β-环糊精作为手性流动相添加剂，研究了酪氨酸甲酯对映体在反相HPLC系统中的拆分，考察了流动相种类、pH和手性流动相添加剂浓度对手性拆分的影响，建立了β-环糊精手性流动相添加剂法拆分酪氨酸甲酯对映体的方法。     

Pirkle型手性固定相拆分盐酸克伦特罗对映体

建立并优化了高效液相色谱手性固定相分离盐酸克伦特罗对映体的方法。使用两种Pirkle型手性固定相(α-Burke-2和Pirkle-1J)拆分了盐酸克伦特罗对映体,考察了缓冲盐添加剂,有机溶剂种类和浓度,以及柱温对保留行为和分离的影响。当流动相为二氯甲烷-乙醇(19:1,V/V)含5 mmol/L乙酸铵,流速2.0 mL/min,柱温20℃时,盐酸克伦特罗对映体在α-Burke-2色谱柱上能实现较好的分离,分离度可达1.85;在Pirkle-1J色谱柱上,分离度可达0.64。盐酸克伦特罗对映体与Pirkle型固定相之间的π-π主客体相互作用和氢键作用是实现对映体分离的最主要分离机制。方法可用于盐酸克伦特罗对映体的质量控制及立体选择性药代动力学的研究。     

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%.     

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.     

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.     

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%).     

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.     

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.     

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.     

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.     

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.