Dynamics and interactions of ibuprofen in cyclodextrin nanosponges by solid-state NMR spectroscopy

• Monica Ferro,
• Franca Castiglione,
• Nadia Pastori,
• Carlo Punta,
• Lucio Melone,
• Walter Panzeri,
• Barbara Rossi,
• Francesco Trotta and
• Andrea Mele

Beilstein J. Org. Chem. 2017, 13, 182–194, doi:10.3762/bjoc.13.21

• the reflexes of IbuNa, shown in upper traces of the figure (Figure 10f). As a final remark, the PXRD patterns show that ibuprofen entrapped into the nanosponge network still retains crystallinity, thus confirming that the formation of the polymer-drug association is a mild process. Conclusion The

Phosphated cyclodextrins as water-soluble chiral NMR solvating agents for cationic compounds

• Cira Mollings Puentes and
• Thomas J. Wenzel

Beilstein J. Org. Chem. 2017, 13, 43–53, doi:10.3762/bjoc.13.6

• . Equation 1 and Equation 2 show the association of the (R)- and (S)-enantiomers of a substrate (Sub) with a chiral solvating agent (CSA). Provided that the exchange of substrates with the CSA is fast on the NMR time scale, there are two mechanisms through which chiral solvating agents (CSAs) can cause

• enantiomeric differentiation. The first is that the complexes of the two enantiomers of the substrate with the enantiomerically pure CSA are diastereomers and therefore exhibit different chemical shifts. The second relies on a frequently observed difference in the association constants of the two enantiomers

• . In those cases where enantiomeric differentiation occurs solely through differences in association constants of the two enantiomers of the substrate with the P-CD, the magnitude of the enantiomeric differentiation may decrease at increasing P-CD concentrations from 5 to 20 mM. In this situation, the

Stabilization of nanosized titanium dioxide by cyclodextrin polymers and its photocatalytic effect on the degradation of wastewater pollutants

• Tamás Zoltán Agócs,
• István Puskás,
• Erzsébet Varga,
• Mónika Molnár and
• Éva Fenyvesi

Beilstein J. Org. Chem. 2016, 12, 2873–2882, doi:10.3762/bjoc.12.286

• occur depending on the conformation of the host–guest complex (if the light-sensitive part of the molecule is located within or outside of the cavity), on the complex association constant and on the concentration ratio of the guest to the CD. It was shown that the photodecomposition of MB was enhanced

• by stabilizing Ag/TiO2 nanoparticles with β-CD, but applying β-CD in excess the rate of degradation decreased dramatically [46]. The association constant of IBR/β-CD complex falls in the range of 103–104 M−1 [47][48], while that of MB/β-CD is less than 103 M−1 [49][50]. According to NMR studies IBR

• is deeply included into the cavity [51], while MB is too large to be completely shielded by complexation. The too strong association between IBR and the cavities of CMBCD-P can be a possible reason of protection instead of catalytic decomposition in this process. Further experiments are needed to

O-Alkylated heavy atom carbohydrate probes for protein X-ray crystallography: Studies towards the synthesis of methyl 2-O-methyl-L-selenofucopyranoside

• Roman Sommer,
• Dirk Hauck,
• Annabelle Varrot,
• Anne Imberty,
• Markus Künzler and
• Alexander Titz

Beilstein J. Org. Chem. 2016, 12, 2828–2833, doi:10.3762/bjoc.12.282

• and Michael Hoffmann (Helmholtz Institute for Pharmaceutical Research Saarland, HIPS) for HRMS measurements. We are grateful to the Helmholtz Association (grant no. VH-NG-934) and the Deutsche Forschungsgemeinschaft (grant no. Ti756/2-1) for financial support.

Direct arylation catalysis with chloro[8-(dimesitylboryl)quinoline-κN]copper(I)

• Sem Raj Tamang and
• James D. Hoefelmeyer

Beilstein J. Org. Chem. 2016, 12, 2757–2762, doi:10.3762/bjoc.12.272

• ) intermediate may be well-stabilized by boron as a Z-type ligand, and the mesityl groups surrounding boron may favor the association of arenes for the deprotonation–metalation and the oxidative addition steps. Wang et al. proposed concerted metalation–deprotonation via a sigma bond metathesis involving a cyclic

Identification, synthesis and mass spectrometry of a macrolide from the African reed frog Hyperolius cinnamomeoventris

• Markus Menke,
• Pardha Saradhi Peram,
• Iris Starnberger,
• Walter Hödl,
• Gregory F.M. Jongsma,
• David C. Blackburn,
• Mark-Oliver Rödel,
• Miguel Vences and
• Stefan Schulz

Beilstein J. Org. Chem. 2016, 12, 2731–2738, doi:10.3762/bjoc.12.269

• towards a biological evaluation of the gland secretion and its compounds to understand their real function in the behavior of the frogs. Although no experimental evidence has been obtained so far, the close association of the innervation of the gland with the mating period, its location and use during

Interactions between cyclodextrins and cellular components: Towards greener medical applications?

• Loïc Leclercq

Beilstein J. Org. Chem. 2016, 12, 2644–2662, doi:10.3762/bjoc.12.261

• binding constants between CDs (α- or γ-CD) and short phospholipids (i.e., diheptanoylphosphatidylcholine, DHPC) [63]. In this study, the association constants were estimated from 1H NMR measurements. The results proved that the K1 values are in the order α-CD < γ-CD while the K2 values are in the order γ

• ]. In the same idea, Mascetti et al. proposed that CDs interact directly with cholesterol [82]. Based on molecular simulations, López et al. proposed the following mechanism: i) association of CDs in aqueous solution to form dimers, ii) binding of dimers at the membrane surface, iii) extraction and

• logical that D-glucose interacts weakly with native CDs due to its size and its hydrophilic property. However, from these conflicting results, Turner proposed to use kinetic measurements to determine the association constants of several sugars with β-CD [98]. This new method has been published in 2000 [99

Radical polymerization by a supramolecular catalyst: cyclodextrin with a RAFT reagent

• Kohei Koyanagi,
• Yoshinori Takashima,
• Takashi Nakamura,
• Hiroyasu Yamaguchi and
• Akira Harada

Beilstein J. Org. Chem. 2016, 12, 2495–2502, doi:10.3762/bjoc.12.244

• selected as a non-ionic molecule with a high association constant to α-CD (Ka = 134 M−1 ) [70]. In the presence of C6 diol, the reaction yields dropped to 63–72%, whereas the molecular weights of the polymers increased (22.9 and 19.4 kDa in entries 3 and 6, respectively). It is considered that by

High performance p-type molecular electron donors for OPV applications via alkylthiophene catenation chromophore extension

• Paul B. Geraghty,
• Calvin Lee,
• Jegadesan Subbiah,
• Wallace W. H. Wong,
• James L. Banal,
• Mohammed A. Jameel,
• Trevor A. Smith and
• David J. Jones

Beilstein J. Org. Chem. 2016, 12, 2298–2314, doi:10.3762/bjoc.12.223

• maximum absorption at 490 nm, while BMR has a maximum absorbance at 541 nm, Table 1. While the BPR and BQR spectra show broad featureless peaks, the spectra for BMR (and BBR) show more complicated structure indicating possible association in solution with the development of strong aggregates. The UV–vis

Experimental and theoretical investigations on the high-electron donor character of pyrido-annelated N-heterocyclic carbenes

• Michael Nonnenmacher,
• Dominik M. Buck and
• Doris Kunz

Beilstein J. Org. Chem. 2016, 12, 1884–1896, doi:10.3762/bjoc.12.178

• for complexes with the unsaturated NHC ligand III, which favors the respective NHC/COapic intermediate by 14.9 kJ/mol. Assuming similar low activation barriers for the CO association and the dissociation, release of the CO ligand from the trigonal plane in the intermediate 3a NHC/COapic leads to the

Sustainable catalysis

• Nicholas J. Turner

Beilstein J. Org. Chem. 2016, 12, 1778–1779, doi:10.3762/bjoc.12.167

• terms of safety and disposal of waste byproducts. Recently, many of these aspects of green chemistry have been the focus of the CHEM21 project (http://www.chem21.eu), funded by the Innovative Medicines Initiative, which is supported by the European Federation of Pharmaceutical Industries Association

Amidofluorene-appended lower rim 1,3-diconjugate of calix[4]arene: synthesis, characterization and highly selective sensor for Cu²⁺

• Rahman Hosseinzadeh,
• Mohammad Nemati,
• Reza Zadmard and
• Maryam Mohadjerani

Beilstein J. Org. Chem. 2016, 12, 1749–1757, doi:10.3762/bjoc.12.163

• interaction with Cu2+. The 1:1 stoichiometry of the obtained complex has been determined by Job’s plot. The association constant determined by fluorescence titration was found to be 1.8 × 106 M−1. The sensor showed a linear response toward Cu2+ in the concentration range from 1 to 10 µM with a detection limit

• fluorescence intensity spectrum showed a gradual decrease up to 5 equiv of Cu2+. With higher Cu2+ concentrations the fluorescence quenched completely (Figure 5a). The stoichiometry of the complex was found to be 1:1 between L and Cu2+ based on the Job’s plot and its association constant was calculated using

• allows a suitable complex formation with a copper ion (Scheme 3). To show the high selectivity of chemosensor L for copper ions, the association constant and limit of detection (LOD) were compared with those reported for other related chemosensors (Table 1). It should be emphasized that due to different

Cyclisation mechanisms in the biosynthesis of ribosomally synthesised and post-translationally modified peptides

• Andrew W. Truman

Beilstein J. Org. Chem. 2016, 12, 1250–1268, doi:10.3762/bjoc.12.120

• tyrosine side chains [17] (Figure 10C). This proposal was confirmed by in vitro reconstitution of PqqE activity with PqqA [128]. Interestingly, PqqE activity is dependent on PqqD, a 10 kDa protein that functions as a chaperone that tightly binds PqqA [129]. This key interaction promotes an association with

From steroids to aqueous supramolecular chemistry: an autobiographical career review

• Bruce C. Gibb

Beilstein J. Org. Chem. 2016, 12, 684–701, doi:10.3762/bjoc.12.69

• sulfate increased guest association, whilst salting-in sodium perchlorate weakened binding considerably. The surprise was that the root cause of the latter was competitive binding of the anions to the hydrophobic pocket of our anionic host. A follow-on full paper expanded in these results considerably and

• provided a detailed thermodynamic picture of how the concentration and nature of salts influence hydrophobic solute association [56]. But why did some salts cause binding to increase? We answered this question back in New Orleans, not

Creating molecular macrocycles for anion recognition

• Amar H. Flood

Beilstein J. Org. Chem. 2016, 12, 611–627, doi:10.3762/bjoc.12.60

• solvents that avoid ion pairing. But, in those cases, the triazolophanes then start to self-associate [17][19]. The story of macrocycle self-association is still unfolding in our hands. None of the multiequilibria fitting would be possible without the use of appropriate software. This allows me to

• where its properties begin to depart from cyanostar’s. This planarity leads to extremely high self-association behavior. While a crystal structure has so far been elusive, the pattern of molecular packing has been examined from studies of surface assembly. We inspected the tricarb macrocycle’s surface

• clean self-association into 2D patterns of fused rosettes (Figure 17c). This pattern allowed us to readily discern binding of iodide anions as bright features constituting a pattern with the same unit-cell dimensions as the parent honeycomb. These macrocycles had another characteristic that was

Interactions between 4-thiothymidine and water-soluble cyclodextrins: Evidence for supramolecular structures in aqueous solutions

• Vito Rizzi,
• Sergio Matera,
• Paola Semeraro,
• Paola Fini and
• Pinalysa Cosma

Beilstein J. Org. Chem. 2016, 12, 549–563, doi:10.3762/bjoc.12.54

• appears to be 1:1 for all examined CDs. Keywords: cyclodextrins; inclusion complex; photodynamic therapy; Introduction Since several years, supramolecular chemistry has been considered the chemistry of the intermolecular bonds inducing the association of several chemical species with the formation of

• superstructures [1][2][3]. The Nobel laureate J. M. Lehn said that “supramolecular chemistry may be defined as chemistry beyond the molecule, bearing on the organized entities of higher complexity that result from the association of two or more chemical species held together by intermolecular forces. Its

• molecule is located inside CDs cavity, the CDs protons, i.e., H3 and H5 are sensitive to the changed environment [52]. If an upfield shift for H3 and H5 protons is observed, an anisotropic shielding effect arisen from the host–guest association can be considered [53]. Indeed, when the inclusion complex is

Self and directed assembly: people and molecules

• Tony D. James

Beilstein J. Org. Chem. 2016, 12, 391–405, doi:10.3762/bjoc.12.42

• to flourish and over the years has been funded by many routes including a TSB project [58] on “A Calibration Free Continuous Invasive Sensor Targeted at Glycaemic Control in the ICU”. This project is worthy of mention since it started a long standing association between myself and John S. Fossey who

Natural products from microbes associated with insects

• Christine Beemelmanns,
• Huijuan Guo,
• Maja Rischer and
• Michael Poulsen

Beilstein J. Org. Chem. 2016, 12, 314–327, doi:10.3762/bjoc.12.34

• toxin indicating an ancient and mutually obligatory association with the host. In another model system, it was also found that the aphid symbiont, Hamiltonella defensa, harbors a prophage that encodes proteinaceous toxins (Shiga-like toxin, cytolethal distending toxin, YD-repeat toxin), which is

• history of the ant–Pseudonocardia association still remains controversial [84][85]. It has been hypothesized that many of the isolated soil-dwelling Actinobacteria may have also been recruited from the environment by horizontal transmission, without having tight evolutionary bonds to the insect host

Interactions of cyclodextrins and their derivatives with toxic organophosphorus compounds

• Sophie Letort,
• Sébastien Balieu,
• William Erb,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2016, 12, 204–228, doi:10.3762/bjoc.12.23

• (ROESY) analysis. Pesticides bearing a nitrogen heterocycle The association constants of chlorpyrifos (4, Figure 3) with β-CD, HP-β-CD, and 6-O-α-maltosyl-β-CD hydrate (G2-β-CD) in aqueous media were determined by photochemically induced fluorescence (PIF, Table 1) [39][46]. Results are summarized in

• and G2-β-CD [39] as a solubility increase is only observed with G2-β-CD. The respective association constants values calculated from the phase solubility diagram were 12 M−1 for K1 (1:1 complex) and 3895 M−1 for K2 (1:2 complex), in good agreement to those obtained by PIF, suggesting an effective

• results, the high association constant observed with γ-CD is mainly due to a good fitting of the pyrimidine ring into the cavity, while one ethoxy substituent protruding from the lower rim. In the cases of α- and β-CD, the phosphoryl residue is located outside the cavity. For α- and β-CD, the methyl

A journey in bioinspired supramolecular chemistry: from molecular tweezers to small molecules that target myotonic dystrophy

• Steven C. Zimmerman

Beilstein J. Org. Chem. 2016, 12, 125–138, doi:10.3762/bjoc.12.14

• bind 9-propyladenine in chloroform with a very high association constant of Kassoc = 120,000 M−1 [17][18][19]. What role do the hydrogen bonding and aromatic stacking play? As seen in Figure 4, this system provides an excellent example of what Jencks called “complex additivity of binding energies” [20

• homologous series of alkanes, not an analysis of a host–guest system. All these values suggest that freezing out a single bond rotation is not terribly costly but association constants can drop significantly if too much flexibility exists; freezing five single bonds within a complex would lower its stability

• Institutes of Health (R01 AR058361), the Muscular Dystrophy Association (295229), and the National Science Foundation (CHE-1307404). I want to thank all of my wonderful students who have made this journey possible. Only some of their work could be included in this review, but I am grateful to them all. This

Supramolecular structures based on regioisomers of cinnamyl-α-cyclodextrins – new media for capillary separation techniques

• Gabor Benkovics,
• Ondrej Hodek,
• Martina Havlikova,
• Zuzana Bosakova,
• Pavel Coufal,
• Milo Malanga,
• Eva Fenyvesi,
• Andras Darcsi,
• Szabolcs Beni and
• Jindrich Jindrich

Beilstein J. Org. Chem. 2016, 12, 97–109, doi:10.3762/bjoc.12.11

• between the cinnamyl moiety and the α-CD cavity would not be strong enough to hold together such large aggregates. According to Boutellier [15] the degree of polymerization (DPmax) for a SP is given by the association constant between the interacting components and by the concentration of the self

Supramolecular polymer assembly in aqueous solution arising from cyclodextrin host–guest complexation

• Jie Wang,
• Zhiqiang Qiu,
• Yiming Wang,
• Li Li,
• Xuhong Guo,
• Duc-Truc Pham,
• Stephen F. Lincoln and
• Robert K. Prud’homme

Beilstein J. Org. Chem. 2016, 12, 50–72, doi:10.3762/bjoc.12.7

• permeation chromatography and light scattering methods [48]. In 2002, Karlson et al. found that hydrophobic association among the hydrophobic substituents of substituted poly(ethylene glycol) was disrupted by host–guest complexation by methylated α-CD [42]; as was a similar association by the hydrophobic

• thickening occurs. 1.3 Recovery of hydrophobic association Hydrophobic associations in substituted polymer solutions may be recovered by adding other guest species which form more stable cyclodextrin host–guest complexes than the polymer substituents do [41][45][46][50]. Thus, Khan et al. used nonionic

• surfactants based on poly(ethylene glycol) to recover the hydrophobic associations in hydrophobically substituted alkali-soluble emulsion (HASE) polymers complexed by α-CD and β-CD [41]. (It should be noted that association occurs between hydrophobically substituted polymers in aqueous solution and that this

Determination of formation constants and structural characterization of cyclodextrin inclusion complexes with two phenolic isomers: carvacrol and thymol

• Miriana Kfoury,
• David Landy,
• Steven Ruellan,
• Lizette Auezova,
• Hélène Greige-Gerges and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2016, 12, 29–42, doi:10.3762/bjoc.12.5

• phase solubility profiles are generally apparent values that combine several effects on the guest solubility: inclusion complexation, self-association of poorly soluble guests, self-aggregation of CD:guest complexes, as well as non-inclusion interaction and micelles formation [38]. The solubilizing

Inclusion complexes of 2-methoxyestradiol with dimethylated and permethylated β-cyclodextrins: models for cyclodextrin–steroid interaction

• Mino R. Caira,
• Susan A. Bourne,
• Halima Samsodien and
• Vincent J. Smith

Beilstein J. Org. Chem. 2015, 11, 2616–2630, doi:10.3762/bjoc.11.281

• information such as the values of the association constants for complex formation in solution. Thus instead, the simpler expedient of determining the solubility of 2ME in a series of aqueous solutions of both native and derivatised cyclodextrins of known concentrations (typically 2% m/v) was initially

Smart molecules for imaging, sensing and health (SMITH)

• Bradley D. Smith

Beilstein J. Org. Chem. 2015, 11, 2540–2548, doi:10.3762/bjoc.11.274

• was vital for efficient rotaxane formation. The interlocked molecule retained its salt binding ability and association of the ions modulated the rotaxane structural dynamics [33][34]. Squaraine rotaxanes The interests in molecular imaging and rotaxane structures merged in 2005 with the discovery and

• , it has to clearly show a pathway that leads to valuable new technologies. Effective biomolecule recognition requires both strong affinity and high selectivity, and for investigators who wish to develop association systems that operate effectively in water I offer two words of advice “surface area

• and self-assembly processes that are crucial for cell growth and signaling. These precisely controlled association systems have been refined over billions of years of evolution. The selective recognition is driven by protein–protein interactions that operate at an interface with a surface area that is