Superstructures with cyclodextrins: Chemistry and applications

• Helmut Ritter

Beilstein J. Org. Chem. 2012, 8, 1303–1304, doi:10.3762/bjoc.8.148

• covalent attachment of CDs to macromolecules and threading of CD molecules onto suitable macromolecular chains could be demonstrated. Unlike other macrocycles such as crown ethers or calixarenes, the cavity of CDs is big enough to include more or less hydrophobic molecules completely. In contrast to

Low-generation dendrimers with a calixarene core and based on a chiral C₂-symmetric pyrrolidine as iminosugar mimics

• Marco Marradi,
• Stefano Cicchi,
• Francesco Sansone,
• Alessandro Casnati and
• Andrea Goti

Beilstein J. Org. Chem. 2012, 8, 951–957, doi:10.3762/bjoc.8.107

• rigidification of the dendrimer structure and the iminosugar presentation in the clusters. The combination of the supramolecular properties of calixarenes with the advantage of a dendrimeric presentation of repetitive units opens up the possibility of generating well-defined multivalent and multifaceted systems

• with more complex and/or biologically relevant iminosugars. Keywords: calixarenes; cation-responsive system; dendrimers; iminosugars; multivalency; Introduction Polyhydroxylated pyrrolidines are one of the main classes of naturally occurring sugar mimics [1][2] and belong to the so-called iminosugars

• , such as calixarenes, with the advantages of a dendrimeric presentation of iminosugar analogues. Calixarenes [11] have been widely employed in host–guest chemistry, first as ligands for small ions and neutral molecules [12][13] and, more recently, for biologically relevant molecules and macromolecules

Enantioselective supramolecular devices in the gas phase. Resorcin[4]arene as a model system

• Caterina Fraschetti,
• Matthias C. Letzel,
• Antonello Filippi,
• Maurizio Speranza and
• Jochen Mattay

Beilstein J. Org. Chem. 2012, 8, 539–550, doi:10.3762/bjoc.8.62

• given complex is faster with BR than with BS. Again, the opposite is true when ξ < 1. A ξ = 1 value corresponds to equal displacement rates irrespective of the configuration of B. Chiral calixarenes, and their resorcinarene relatives, can be characterized by a variable conformational flexibility. They

• achiral subunits forming a chiral macrocyclic scaffold. Chiral centers in the side chains Flexible peptidoresorcin[4]arenes as chiral selectors of dipeptides. In 2002, the first investigations of chiral recognition by calixarenes in the gas phase were carried out in Rome by the group of Prof. Speranza by

Fifty years of oxacalix[3]arenes: A review

• Kevin Cottet,
• Paula M. Marcos and
• Peter J. Cragg

Beilstein J. Org. Chem. 2012, 8, 201–226, doi:10.3762/bjoc.8.22

• species. Applications in fields as diverse as ion selective electrode modifiers, fluorescence sensors, fullerene separations and biomimetic chemistry are described. Keywords: calixarenes; host–guest chemistry; macrocycles; oxacalixarenes; Introduction Calixarenes, macrocycles which are widely used in

• supramolecular chemistry, are 2,6-metacyclophanes with a methylene bridge between their phenolic groups, as shown in Figure 1 [1][2][3]. In 1994, the term “homocalixarene” was coined by Brodesser and Vögtle to describe analogues of calixarenes with two or more methylene groups between the aromatic moieties [4

• complementarity between the arrangement of phenolic groups and the preferred coordination environment of Na+. Removal of the tert-butyl groups through a conventional AlCl3 driven retro-Friedel–Crafts de-tert-butylation reaction, as seen in other calixarenes, is unsuccessful in the case of oxacalixarenes

Structural conditions required for the bridge lithiation and substitution of a basic calix[4]arene

• Conrad Fischer,
• Wilhelm Seichter and
• Edwin Weber

Beilstein J. Org. Chem. 2011, 7, 1602–1608, doi:10.3762/bjoc.7.188

• ], whereas we follow a route involving the formation of a methylene carbanion through lithiation, which by nucleophilic substitution forms the desired bridge-substituted calixarenes [4][5]. While the number of substituted methylene atoms in the first protocol depends clearly on the amount of N

• involving the addition of small amounts of NaI and acetronitrile-d3 to the CDCl3 solution, fixation of the calixarenes in a pure cone conformation was achieved (Figure 2). Separate lithiation of the two mixed ethers 11 and 12 followed by the addition of CO2 results in the desired carboxylic acid derivatives

Anion–π interactions influence pK_a values

• Christopher J. Cadman and
• Anna K. Croft

Beilstein J. Org. Chem. 2011, 7, 320–328, doi:10.3762/bjoc.7.42

• ]. The magnitude of the anion–π interaction varies with the size of the aromatic quadrupole and the polarisability of the system. Recent quantitative measurements of chloride binding to calixarenes in solution estimate these interactions to be as much as 4.6 kJ·mol−1 [18]. Moreover, computational models

Calix[4]arene-click-cyclodextrin and supramolecular structures with watersoluble NIPAAM-copolymers bearing adamantyl units: “Rings on ring on chain”

• Bernd Garska,
• Monir Tabatabai and
• Helmut Ritter

Beilstein J. Org. Chem. 2010, 6, 784–788, doi:10.3762/bjoc.6.83

• superstructures, CDs and calixarenes turned out to be very attractive not only as molecular receptors but also as building blocks for the construction of supramolecular architectures [5]. For that reason, we were encouraged to couple these two different types of macrocycles via click type reactions. Recent

• progress in the field of supramolecular chemistry is based on click chemistry, a versatile and powerful tool that permits the modular assembly of new molecular entities [6][7]. Both CDs as well as calixarenes have already been modified by click chemistry [8][9][10][11][12][13][14]. However, the coupling of

• calixarenes and β-CD via click reaction and their application in the field of supramolecular chemistry has not yet been reported. Herein, we describe the synthesis and complexation behavior of a dual type calix[4]arene-click-cyclodextrin (4) receptor by the cycloaddition of a dipropargylether of calix[4]arene

Molecular recognition of organic ammonium ions in solution using synthetic receptors

• Andreas Späth and
• Burkhard König

Beilstein J. Org. Chem. 2010, 6, No. 32, doi:10.3762/bjoc.6.32

• develop synthetic receptors for their selective molecular recognition. The type of host compounds for organic ammonium ion binding span a wide range from crown ethers to calixarenes to metal complexes. Typical intermolecular interactions are hydrogen bonds, electrostatic and cation–π interactions

• ]. Many types of synthetic ammonium ion receptors are available, ranging from crown ethers, calixarenes, porphyrins, cucurbiturils, cyclodextrins and cyclopeptides to tweezer ligands, sterically geared tripods and several types of metal complexes. The most important methods used for evaluating ammonium

• substance classes that have been mostly used in organic ammonium ion recognition: crown ethers, calixarenes [54], cyclodextrins [55][56][57], cucurbiturils, porphyrins, phosphonate based receptors, tripodal receptors, tweezer ligands, clefts, cyclopeptides and metal complexes. We have not included rotaxanes

Synthesis and properties of calix[4]arene telluropodant ethers as Ag⁺ selective sensors and Ag⁺, Hg²⁺ extractants

• Yang Lu,
• Yuanyuan Li,
• Song He,
• Yan Lu,
• Changying Liu,
• Xianshun Zeng and
• Langxing Chen

Beilstein J. Org. Chem. 2009, 5, No. 59, doi:10.3762/bjoc.5.59

• their potential receptor properties for cations, anions and neutral molecules, calixarenes have enjoyed widespread use in various areas of science and technology. One of their successful applications as sensors is in analytical chemistry. They are useful for separations, enrichment, and analyses of

• ionic and neutral molecular species [1][2][3][4]. In particular, the ion-selective electrode (ISE) is an important target in analytical applications [5][6][7][8][9][10]. To improve the ion selectivity of calixarenes, a great deal of effort has been devoted to the design and synthesis of novel

• functionalized calixarenes in recent years [1][2][3][4]. In fact, a large number of calixarene derivatives containing pendant ether, amide, ketonic, ester and crown ether groups have been employed in studies of ISEs sensitive to sodium ions [11][12][13][14][15][16][17][18][19][20], potassium ions [21][22][23][24

Synthesis of deep- cavity fluorous calix[4]arenes as molecular recognition scaffolds

• Maksim Osipov,
• Qianli Chu,
• Steven J. Geib,
• Dennis P. Curran and
• Stephen G. Weber

Beilstein J. Org. Chem. 2008, 4, No. 36, doi:10.3762/bjoc.4.36

• ; organofluorine; (perfluoroalkyl)alkyl aryl ethers; Introduction Calixarenes [1] are one of the most useful types of macrocyclic scaffolds. Since first reported by Zinke and Ziegler [2], calix[4]arenes have been used for a variety of molecular recognition, nanotechnology, and supramolecular applications. These

• extraction of organic substrates into a fluorous liquid phase via hydrogen bonding [21]. Combining the selective nature of fluorous chemistry with the extensive molecular recognition capabilities of calixarenes should generate a scaffold for selective molecular receptors, yet few reports exist that detail

• the synthesis and applications of fluorous calixarenes [22][23][24][25][26]. There are no reports of studies of solubilities of such calixarenes in fluorous solvents. The work reported herein is focused on synthesizing fluorous calixarenes that are easily functionalized for selective molecular