超两亲分子:可控组装与解组装

与基于共价键的两亲性分子相对照,超两亲分子系指基于非共价键构筑的两亲分子.基于超分子体系的分子工程学的思想,本文总结了超两亲分子的各种类型,包括小分子型、聚合物型和响应性超两亲分子等,以及组装超两亲分子的各种推动力,如主客体相互作用、基于电荷转移作用和不同分子间的协同作用等.研究表明,超两亲分子的研究既可丰富传统的胶体界面化学,又为高级结构的可控组装提供了新的构筑基元,并为制备功能超分子材料开拓了新的途径.     

肽超分子自组装:结构调控和功能化

生物分子自组装对生物体有重要意义,利用生物分子构筑具有功能性的有序组装体一直是人们关注的焦点.肽分子是一类重要的组装基元,肽的超分子自组装可形成多种纳米或微米尺度的结构,并可应用于能源、医药等领域.如何实现肽自组装结构的精准调控以及精准调控肽自组装实现功能化,是目前该领域面临的新挑战.肽的自组装是基于非共价键力的协同作用实现的,通过各种因素调节这些非共价键力的作用,是实现自组装结构调控和功能化的关键.虽然自组装结构调控可以通过改变外部环境调控,但是通过精确分子设计、组装基元分子间的相互作用调控可以更好地实现结构的精准调控;并有利于进一步通过引入功能性分子作为组装基元,实现自组装体的功能化.本文将针对肽自组装体的结构调控以及功能化两个方面对相关研究进行综述.     

二苯丙氨酸短肽手性结构的可控组装

以阳离子二苯丙氨酸（Cationic dipeptide,CDP）为组装基元,通过控制熟化时间,在乙醇溶液中分别获得了平滑的纳米纤维和螺旋纤维结构.通过红外光谱和圆二色光谱系统研究了CDP在乙醇溶液中的组装体随时间的变化.研究发现,CDP在乙醇中可以组装成纳米纤维的结构.随着在乙醇中熟化时间的增加,CDP纳米纤维发生扭曲,最终组装成绳状的螺旋纤维结构.光谱数据分析表明纳米纤维转变成螺旋纤维主要源于相邻肽分子中的正电荷之间的强静电排斥作用和肽分子间氢键作用控制的β-折叠二级结构.这项工作通过简单的控制熟化时间实现了对超分子组装体结构的调控,为超分子手性组装体的可控制备提供了一种简单可行的方法.     

基于冠醚衍生物的超分子聚合物

自组装现象是生命科学最本质的内容之一,生物体系可以精确地利用非共价键相互作用形成高度有序的功能组装体.受到大自然的启发,近年来利用分子自组装构筑包括超分子聚合物在内的有序聚集体是超分子科学的研究热点.此类组装体不仅在拓扑学上具有重要的意义,而且可以用来制备动态的超分子功能材料.冠醚作为第一代超分子主体化合物,由于其结构...     

界面超分子聚合

超分子聚合物诞生于高分子化学与超分子化学的交叉融合,一般是指单体间通过非共价键作用连接形成的聚合物,并在溶液或体相中表现出类似聚合物的性质。目前超分子聚合物一般通过均相溶液聚合制备得到,但溶液中的超分子聚合是一个自发的组装过程,具有浓度依赖性,组装过程不易可控。为解决此问题,研究人员可以将超分子聚合从均相溶液转移到界面,在界面上可控地制备超分子聚合物。通过界面聚合制备超分子聚合物具有一些独特的优势,如可以制备得到分子量更高的超分子聚合物,易于制备一些缺陷少、面积大、有序的二维超分子聚合物等。本文基于在液-液、气-液和固-液三种界面上制备超分子聚合物的一些代表性工作,介绍了界面超分子聚合方法和应用,并展望其未来发展。     

聚合物多层膜的表面分子工程

概述了作者及其研究群体发展的基于氢键、配位键和共价键的聚合物交替沉积组装方法.在此基础上,重点讨论将溶液中的超分子组装与界面交替沉积相结合的非常规界面交替沉积组装方法.通过结构构筑与功能组装的结合,实现了不同表面物理化学性质的可控调节,包括仿生矿化、超疏水涂层、可控组装与释放、表面分子印迹等.这些研究结果对发展基于聚合物多层膜的表面分子工程具有重要意义.     

从超分子聚合物到超分子有机框架:组装溶液相超分子结构的周期性

单体分子在溶液相自发形成周期性的网络结构,是超分子化学和分子自组装研究领域的重大挑战.多头基分子在溶液相通过分子间非共价键作用可以形成超分子聚合物.提高多头基(三头基和四头基)分子骨架的刚性,可以提高结合位点的结构预组织,进而增强分子间相互作用的协同性和多价性特征,提高自组装结构的有序性或周期性.本文综述了多头基分子自组装形成超分子聚合物的一些重要进展,介绍了二维超分子有机框架(一类新的溶液相周期性自组装网络结构研究的最新进展.     

自组装共混制备PEG化基因载体

通过含PEG链段的两亲聚合物的自组装共混, 制备了基于疏水作用力的新型PEG化非病毒基因载体. 分别选用胆固醇-聚乙二醇和聚乙二醇-聚丙二醇-聚乙二醇作为共混改性剂, 研究两亲聚合物的种类对组装体在生理盐溶液中的稳定性及基因转染效率的影响. 结果表明, 疏水驱动力的大小是获得稳定的PEG化基因超分子组装体的关键. 通过对两亲聚合物中疏水链段的选择调控, 可制备稳定的PEG化基因超分子组装体, 提高基因传递体系在生理盐溶液中的稳定性及基因转染效率. 通过自组装共混, 为新型PEG化基因超分子组装体的制备提供了切实可行的新方法.     

超分子有机框架:水相周期性自组装孔结构

概述了水相超分子有机框架组装方面最近的进展. 在简述了利用多头基单体构筑超分子组装体的背景之后, 介绍了利用三头基和四头基分子形成超分子网络组装体的重要例子, 着重描述了利用刚性预组织平面三角形单体和四面体单体, 通过葫芦脲[8]对4-苯基吡啶盐堆积二聚体的包结作用, 在水相构筑二维和三维超分子有机框架的进展, 并简要叙述了在水相表征周期性自组装结构的仪器分析方法. 最后就超分子有机框架构筑的单体设计及其可能的应用及功能做了分析与展望.     

基于超分子环糊精两亲分子的敏感型囊泡体系

敏感型囊泡可初步概括为由两亲分子通过非共价键构筑的、对外界的刺激具有特色响应性的一类新型囊泡体系。由"超分子环糊精两亲分子"自组装形成的囊泡体系是该类体系中重要的一类。本文重点介绍了环糊精参与的"超分子环糊精两亲分子"囊泡体系的研究进展。以与环糊精复合的化合物结构类型不同进行分类,介绍了该类囊泡体系的制备以及该体系在医药工程、新型"智能"材料以及生物模拟等方面的潜在应用;结合现阶段的研究状况,对该类囊泡体系的发展前景进行了展望。     

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.     

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.     

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.     

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.     

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.     

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.