Asymmetric Michael addition reactions catalyzed by calix[4]thiourea cyclohexanediamine derivatives

• Zheng-Yi Li,
• Hong-Xiao Tong,
• Yuan Chen,
• Hong-Kui Su,
• Tangxin Xiao,
• Xiao-Qiang Sun and
• Leyong Wang

Beilstein J. Org. Chem. 2018, 14, 1901–1907, doi:10.3762/bjoc.14.164

• and yields of the Michael reactions. Supramolecular catalysis has drawn tremendous interest in the past few years [15][16][17][18][19][20][21][22][23]. In this context, calixarenes are ideal supramolecular macrocyclic scaffolds for the design of molecular receptors and organocatalysts due to their

• , this may offer us the opportunity to improve the green aspect of many reactions both in organic and aqueous medium [30]. For example, it has been reported that calixarenes linked with thiourea groups can be used to catalyze asymmetric Aldol reactions or Michael addition reactions in recent years [31

• ][32][33]. Compared with the lower rim in the cone conformation of calixarenes, the functionalization of the upper rim is more challenging. Notably, it should be more valuable to exploit the cavity of upper rim-functionalized calixarenes because of the possibility of simultaneously using the

Strong binding and fluorescence sensing of bisphosphonates by guanidinium-modified calix[5]arene

• Jie Gao,
• Zhe Zheng,
• Lin Shi,
• Si-Qi Wu,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2018, 14, 1840–1845, doi:10.3762/bjoc.14.157

• particularly suitable for the detection of analytes lacking chromophores. The key factor in IDA is the rational design of artificial receptors that are capable of binding analytes strongly and specifically. Calixarenes are the third generation of macrocyclic receptors after crown ethers and cyclodextrins. Due

• to their facial modification, Prof. Böhmer demonstrated calixarenes as having “(almost) unlimited possibilities” [17]. We have focused on molecular recognition and self-assembly of water-soluble calixarene derivatives for a long time [18][19][20][21][22][23][24], directed by exploring biomedical

Synthesis and photophysical studies of a multivalent photoreactive Ru^II-calix[4]arene complex bearing RGD-containing cyclopentapeptides

• Sofia Kajouj,
• Lionel Marcelis,
• Alice Mattiuzzi,
• Adrien Grassin,
• Damien Dufour,
• Pierre Van Antwerpen,
• Didier Boturyn,
• Eric Defrancq,
• Mathieu Surin,
• Julien De Winter,
• Pascal Gerbaux,
• Ivan Jabin and
• Cécile Moucheron

Beilstein J. Org. Chem. 2018, 14, 1758–1768, doi:10.3762/bjoc.14.150

• involved in the angiogenesis process [60]. Furthermore, the use of calixarenes for biological applications is the subject of intensive researches. They are indeed exploited in various areas such as surface recognition, structural mimes or membrane receptor inhibition [61][62][63], and it was also shown

• that calixarenes themselves display antibacterial, antiviral, and anticancer properties [64]. Herein, we describe the synthesis of a multivalent phototherapeutic agent designed in order to specifically target membrane receptors involved in the angiogenesis process. The multivalent system is composed of

Host–guest complexes of conformationally flexible C-hexyl-2-bromoresorcinarene and aromatic N-oxides: solid-state, solution and computational studies

• Rakesh Puttreddy,
• Ngong Kodiah Beyeh,
• S. Maryamdokht Taimoory,
• Daniel Meister,
• John F. Trant and
• Kari Rissanen

Beilstein J. Org. Chem. 2018, 14, 1723–1733, doi:10.3762/bjoc.14.146

• intramolecular O···H–O hydrogen bonds (HBs) [1][2]. The combination of their confined cavity and conformational flexibility has driven the interest in these synthetic receptors [3], a subclass of calixarenes [4], for a wide range of applications in fields such as catalysis [5][6][7][8][9], sensors [10][11

A conformationally adaptive macrocycle: conformational complexity and host–guest chemistry of zorb[4]arene

• Liu-Pan Yang,
• Song-Bo Lu,
• Arto Valkonen,
• Fangfang Pan,
• Kari Rissanen and
• Wei Jiang

Beilstein J. Org. Chem. 2018, 14, 1570–1577, doi:10.3762/bjoc.14.134

• macrocycles possess multiple conformers due to the naphthalene flipping in analogy with the phenyl-ring flipping seen in the more common calixarenes. The conformers so formed undergo quick interconversion and each one has a slightly different cavity. Thus, these conformers consist of a complex conformational

Hyper-reticulated calixarene polymers: a new example of entirely synthetic nanosponge materials

• Alberto Spinella,
• Marco Russo,
• Antonella Di Vincenzo,
• Delia Chillura Martino and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2018, 14, 1498–1507, doi:10.3762/bjoc.14.127

• efficiency indeed depends on the effective occurrence of both electrostatic and hydrophobic interactions between the guest and the polymer lattice. Thus, our CaNS nanosponges can be considered as a new class of purely synthetic smart absorbent materials. Keywords: calixarenes; nanosponges; smart materials

• report on the synthesis and characterization (FTIR, solid-state NMR, SEM) of a new class of entirely synthetic nanosponge materials based on calixarenes (CaNSs), by reacting a tetrakis(propargyloxy)calix[4]arene with alkyl diazides. The synthesis was accomplished by means of a classical “click” approach

Recent applications of chiral calixarenes in asymmetric catalysis

• Mustafa Durmaz,
• Erkan Halay and
• Selahattin Bozkurt

Beilstein J. Org. Chem. 2018, 14, 1389–1412, doi:10.3762/bjoc.14.117

• Analysis Technological Application and Research Center (UBATAM), Usak University, Usak, Turkey Vocational School of Health Services, Usak University, 64200 Usak, Turkey 10.3762/bjoc.14.117 Abstract The use of calixarenes in asymmetric catalysis is receiving increasing attention due to their tunable three

• -dimensional molecular platforms along with their easy syntheses and versatile modification at the upper and lower rims. This review summarizes the recent progress of synthesis and use of chiral calixarenes in asymmetric syntheses which emerged later than 2010. Keywords: asymmetric catalysis; chiral

• asymmetric catalysis has received considerable interest and witnessed significant progress in recent years [2][3][4]. Calixarenes are considered as the third generation of supramolecular hosts after cyclodextrins and crown ethers [5][6]. Due to their easy preparation and readily modification at either the

A selective removal of the secondary hydroxy group from ortho-dithioacetal-substituted diarylmethanols

• Anna Czarnecka,
• Emilia Kowalska,
• Agnieszka Bodzioch,
• Joanna Skalik,
• Marek Koprowski,
• Krzysztof Owsianik and
• Piotr Bałczewski

Beilstein J. Org. Chem. 2018, 14, 1229–1237, doi:10.3762/bjoc.14.105

• been used in the treatment of overactive bladder, external genital warts and osteoporosis (Figure 1). The diarylmethyl motif also plays a pivotal role in supramolecular architectures of calixarenes [13] and orthocyclophanes [14]. A special, ortho-carbonyl-substituted diarylmethyl scaffold is present in

On the design principles of peptide–drug conjugates for targeted drug delivery to the malignant tumor site

• Eirinaios I. Vrettos,
• Gábor Mező and
• Andreas G. Tzakos

Beilstein J. Org. Chem. 2018, 14, 930–954, doi:10.3762/bjoc.14.80

• vehicles and formulates like nanoparticles [24] and calixarenes or cyclodextrins [25][26], where the cytotoxic drug is loaded and can be released at the malignant tumor site; b) installation of labile chemical groups to the tumor microenvironment (i.e., low pH) able to mask the cytotoxic drug and form a

Nanoreactors for green catalysis

• M. Teresa De Martino,
• Loai K. E. A. Abdelmohsen,
• Floris P. J. T. Rutjes and
• Jan C. M. van Hest

Beilstein J. Org. Chem. 2018, 14, 716–733, doi:10.3762/bjoc.14.61

• calixarenes [38][39]. Besides these supramolecular cage structures compartmentalization can also be achieved in macromolecular nanoreactors. The advantage of employing these polymeric structures is their improved robustness and loading capacity, which makes recycling and efficient usage of catalytic species

From dipivaloylketene to tetraoxaadamantanes

• Gert Kollenz and
• Curt Wentrup

Beilstein J. Org. Chem. 2018, 14, 1–10, doi:10.3762/bjoc.14.1

• complexes, which is typical for capped calixarenes [43]. However, the lower rim is very congested, thereby hindering the endohedral addition of water to the bisdioxine unit, and in fact a tetraoxaadamantane derivative was not formed. Conclusion The stable 1,3-dioxin-4-one ketene derivative 3 is obtained by

Binding abilities of a chiral calix[4]resorcinarene: a polarimetric investigation on a complex case of study

• Marco Russo and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2698–2709, doi:10.3762/bjoc.13.268

• evaluation of the relevant binding constants. We were interested in verifying if the same technique could be suitably applied to other classes of chiral hosts. Thus, proline-modified calixarenes or calixresorcinarenes appeared ideal testing candidates. It is also worth noting that, because of the large

• occurring in host–guest complex formation processes involving calixarenes in general. This can be particularly useful, even because CAP and structurally related ligands might find various interesting applications, due to their amphiphilic character, chirality and coordination ability towards metal cations

Glyco-gold nanoparticles: synthesis and applications

• Federica Compostella,
• Olimpia Pitirollo,
• Alessandro Silvestri and
• Laura Polito

Beilstein J. Org. Chem. 2017, 13, 1008–1021, doi:10.3762/bjoc.13.100

• [45][56][57][58]. Prosperi and co-workers coated dodecanthiol AuNPs with manno-calixarenes exploiting hydrophobic interactions, obtaining an efficient targeting against cancer cells [56]. Similarly, a reversible addition−fragmentation chain transfer (RAFT) polymerization approach has been exploited

Interactions between photoacidic 3-hydroxynaphtho[1,2-b]quinolizinium and cucurbit[7]uril: Influence on acidity in the ground and excited state

• Jonas Becher,
• Daria V. Berdnikova,
• Darinka Dzubiel,
• Heiko Ihmels and
• Phil M. Pithan

Beilstein J. Org. Chem. 2017, 13, 203–212, doi:10.3762/bjoc.13.23

• , cyclodextrins, calixarenes or cucurbiturils, usually has a significant influence on their chemical and physicochemical properties [1][2]. Among the most efficient and versatile host systems along these lines are cucurbit[n]urils (CB[n]) [3][4][5], that consist of methylene-linked glycoluril units that create a

Advances in the synthesis of functionalised pyrrolotetrathiafulvalenes

• Luke J. O’Driscoll,
• Sissel S. Andersen,
• Marta V. Solano,
• Dan Bendixen,
• Morten Jensen,
• Troels Duedal,
• Jess Lycoops,
• Cornelia van der Pol,
• Rebecca E. Sørensen,
• Karina R. Larsen,
• Kenneth Myntman,
• Christian Henriksen,
• Stinne W. Hansen and
• Jan O. Jeppesen

Beilstein J. Org. Chem. 2015, 11, 1112–1122, doi:10.3762/bjoc.11.125

• systems [11][27], to the incorporation of MPTTFs and BPTTFs into more complex molecular architectures such as macrocycles [8][9][14], calix-pyrroles [1][10][11], calixarenes [29] and porphyrins [30]. Note that for MPTTFs, R1 and R2 can be either the same or different. Here, we present recent developments

Tuning of tetrathiafulvalene properties: versatile synthesis of N-arylated monopyrrolotetrathiafulvalenes via Ullmann-type coupling reactions

• Vladimir A. Azov,
• Diana Janott,
• Dirk Schlüter and
• Matthias Zeller

Beilstein J. Org. Chem. 2015, 11, 860–868, doi:10.3762/bjoc.11.96

• nature on the aromatic group, as well as can be employed with substituted and non-substituted MPTTFs, opening the way for its application for the synthesis of more complex molecular systems, such as conjugates with non-protected calixarenes. New aromatic-MPTTF conjugates were characterized using

Inherently chiral calix[4]arenes via oxazoline directed ortholithiation: synthesis and probe of chiral space

• Simon A. Herbert,
• Laura J. van Laeren,
• Dominic C. Castell and
• Gareth E. Arnott

Beilstein J. Org. Chem. 2014, 10, 2751–2755, doi:10.3762/bjoc.10.291

• shown to be significant [14][15][16][17]. With this in mind, chiral calixarenes have been synthesized, either by the incorporation of a chiral group into the calixarene scaffold, or by the introduction of asymmetry into the structure itself, creating chirality associated with form and termed inherent

• chirality [18]. Efforts to explore the properties of inherently chiral calixarenes have been hampered by the difficulty with which enantiomerically pure or enriched antipodes can be obtained. Until recently, no significantly asymmetric method for functionalizing calix[4]arenes had been developed, with all

• inherently chiral calixarenes to be obtained, in good enantiomeric ratios (Scheme 1). We reasoned though that the diastereoselectivity of the reaction would be even better if a more bulky oxazoline was employed, i.e., using a tert-butyl group. Herein we report our results on the use of tert-butyloxazolines

Clicked and long spaced galactosyl- and lactosylcalix[4]arenes: new multivalent galectin-3 ligands

• Silvia Bernardi,
• Paola Fezzardi,
• Gabriele Rispoli,
• Stefania E. Sestito,
• Francesco Peri,
• Francesco Sansone and
• Alessandro Casnati

Beilstein J. Org. Chem. 2014, 10, 1672–1680, doi:10.3762/bjoc.10.175

• activity [6]. Furthermore, Gal-3 can act as a competitive inhibitor against Gal-1 which, on the other side, induces anoikis of tumor cells [7][8]. Glycocalixarenes [9][10][11][12], calixarenes [13][14][15] adorned with carbohydrates at the upper and/or at the lower rims, have been demonstrated to be

• interaction with the protein in solution [38] and is tailored to have the immobilized protein properly oriented for the interaction with ligands. The sensorgrams shown in Figure 3 were obtained by fluxing an 1 mM solution of calixarenes over the protein-coated chip. The small increases of resonance units in

• the sensograms (Figure 3) showed a weak affinity of all calixarenes for Gal-3. However, the three synthetic molecules showed a very similar trend of Gal-3 binding affinity in three independent measurements (experiments A, B and C in Figure 4a). In particular, glycocalixarene 3 (cone structure, four

Topochemical control of the photodimerization of aromatic compounds by γ-cyclodextrin thioethers in aqueous solution

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2013, 9, 1858–1866, doi:10.3762/bjoc.9.217

• smallest possible templates for the control of photoreactions. Such a host provides a well-defined nano environment, a so-called molecular reaction vessel [6], which can catalyze and direct particular transformations. Calixarenes [7], cucurbiturils [8][9], and cyclodextrins (CDs) [10][11][12][13][14][15

Host–guest complexes of mixed glycol-bipyridine cryptands: prediction of ion selectivity by quantum chemical calculations, part V

• Svetlana Begel,
• Ralph Puchta and
• Rudi van Eldik

Beilstein J. Org. Chem. 2013, 9, 1252–1268, doi:10.3762/bjoc.9.142

• have been investigated experimentally as well as by computational methods to gain information about the geometric and electronic demands of this process [7][8][9][10]. Well-known supramolecular species, e.g., calixarenes [11][12][13][14][15], cyclodextrines [16], crown ethers [17][18][19][20][21][22

Molecular solubilization of fullerene C₆₀ in water by γ-cyclodextrin thioethers

• Hai Ming Wang and
• Gerhard Wenz

Beilstein J. Org. Chem. 2012, 8, 1644–1651, doi:10.3762/bjoc.8.188

• hampered by the toxicities of the employed organic solvents or surfactants. The most successful strategy to carry the extremely hydrophobic C60 molecule into water is the use of appropriate water-soluble carriers that can form host–guest complexes, such as calixarenes [19][20] and cyclodextrins (CDs) [21

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