Enabling technologies and green processes in cyclodextrin chemistry

• Giancarlo Cravotto,
• Marina Caporaso,
• Laszlo Jicsinszky and
• Katia Martina

Beilstein J. Org. Chem. 2016, 12, 278–294, doi:10.3762/bjoc.12.30

• preparation of CD thiols and thioethers is an emerging challenge because of the importance of intermediary azido derivatives [96] and favorable aggregation properties in nanomedicines and particularly the antidote Sugammadex [97]. The reaction between 6I-O-monotosyl-β-CD and various nucleophiles opens a new

My maize and blue brick road to physical organic chemistry in materials

• Anne J. McNeil

Beilstein J. Org. Chem. 2016, 12, 229–238, doi:10.3762/bjoc.12.24

• emerged was a beautiful story [3][4][5] (and method) that is still being used to determine the aggregation state of lithium enolates [6][7][8][9] and alkoxides [10][11][12][13]. From Dave, I learned a tremendous amount about being a scientist. One of the most important take-home messages was that all data

• structures, such as ribbons, fibers, and sheets. This self-aggregation is driven by noncovalent interactions, including hydrogen bonding, π stacking, van der Waals interactions, and halogen bonding. Physical interactions amongst these larger structures lead to gel formation. Because noncovalent interactions

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

• homosupramolecular interactions between the same species were missing. This work clearly demonstrates that the intermolecular complex formation is a regioselective process where the CD cavity can differentiate between the positional isomers which will result in different aggregation behavior of the regioisomers

• prepare the two regioisomers of Cin-α-CD in gram-scale which was required for the detailed characterization of their aggregation ability and for their application in capillary electrophoresis (CE). The monosubstituted products were characterized by ESI mass spectrometry, 1H NMR and 13C NMR spectroscopy

• aggregation was observed for both derivatives (see Record 3 in Figure 7 and Figure 8). Those were present in molecularly dispersed form with a Dh around 1.25 nm, which corresponds to the size of the unmodified, non-aggregated α-CD [14]. These results are in agreement with the results obtained by NMR

Aggregation behavior of amphiphilic cyclodextrins in a nonpolar solvent: evidence of large-scale structures by atomistic molecular dynamics simulations and solution studies

• Giuseppina Raffaini,
• Fabio Ganazzoli and
• Antonino Mazzaglia

Beilstein J. Org. Chem. 2016, 12, 73–80, doi:10.3762/bjoc.12.8

• nanoaggregates even in apolar solvents. Keywords: aggregation; amphiphilic cyclodextrins; molecular dynamics; nanoparticles; self-assembly; simulations; Introduction Amphiphilic cyclodextrins (aCD) are a class of molecules highly investigated for their self-assembly properties and inherent potential

• molecular recognition [3] or nanocarriers for drug delivery [4]. In the recent past, the aggregation behavior of aCD was investigated in water, getting insights on the structures of free nanoassemblies [5][6] or in combination with therapeutic agents [7]. However, in some stages of preparation and

• of the initial aggregation stage could easily take place. In particular, these simulations carried out with relatively small systems comprising a few molecules allowed us to assess that the driving force for aggregation was due to a synergy of different contributions. In particular, we found that the

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

• carboxylate on average. This was attributed to aggregation of the dimers as a consequence of their amphiphilic nature, complexation of the octamethylene linker in the β-CD dimer annuli, and hydrogen bonding interactions between their β-CD annuli. The 1:1 complexation constants, 10−4K11 = 7.96, 2.32 and 26.42

• found that the adamantyl substituents aggregate in aqueous solution to form a micelle and that subsequent addition of α-CD leads to the formation of a supramolecular hydrogel as shown in Figure 11 [88]. The driving force for gelation is a combination of the hydrophobic aggregation of the adamantyl

• substituents and the aggregation of the α-CD complexed portions of the AD-PEG chains. Part of the interest in these low molecular weight polymer systems arises because they are able to pass through the kidney membrane [89] and are consequently of interest as components of drug-delivery systems [89][90]. A

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

Polydisperse methyl β-cyclodextrin–epichlorohydrin polymers: variable contact time ¹³C CP-MAS solid-state NMR characterization

• Isabelle Mallard,
• Davy Baudelet,
• Franca Castiglione,
• Monica Ferro,
• Walter Panzeri,
• Enzio Ragg and
• Andrea Mele

Beilstein J. Org. Chem. 2015, 11, 2785–2794, doi:10.3762/bjoc.11.299

• absence of light diffraction, as expected in the case of toluene aggregation, was controlled by recording the UV–vis absorption spectra in the visible region (400–700 nm), outside the absorption range of toluene. As flattened signals with absorbances close to zero were obtained for all of the mixtures

Enantioselective additions of copper acetylides to cyclic iminium and oxocarbenium ions

• Jixin Liu,
• Srimoyee Dasgupta and
• Mary P. Watson

Beilstein J. Org. Chem. 2015, 11, 2696–2706, doi:10.3762/bjoc.11.290

• , indicting that catalyst aggregation occurs under these reaction conditions [58]. It is unclear at this point, whether these catalyst aggregates are on or off the catalytic cycle. Conclusion As described above, highly enantioselective, copper-catalyzed alkynylations of cyclic iminium and oxocarbenium ion

Synthesis and photophysical characteristics of polyfluorene polyrotaxanes

• Aurica Farcas,
• Giulia Tregnago,
• Ana-Maria Resmerita,
• Pierre-Henri Aubert and
• Franco Cacialli

Beilstein J. Org. Chem. 2015, 11, 2677–2688, doi:10.3762/bjoc.11.288

• results [50]. Interestingly, 3·TM-γCD shows a much stronger 0–1 transition than the 0–0 one, as the non-rotaxane copolymer 3, which might be indicative of some aggregation even though we do not observe a strong tail in the 500–600 nm regions (apart from the minor red-shift mentioned earlier). We also note

Assembly of synthetic Aβ miniamyloids on polyol templates

• Sebastian Nils Fischer and
• Armin Geyer

Beilstein J. Org. Chem. 2015, 11, 2646–2653, doi:10.3762/bjoc.11.284

• the first step of Aβ oligomerization. In the present article, we further develop the idea of systematic variation of the oligomerization degree of Aβ fragments by using dynamic covalent chemistry for the assembly of miniamyloids. The size of a polyol template will limit the aggregation degree of Aβ

• chemistry is the self-correcting reversibility if individual peptides which are bound in the wrong orientation resulting in a strong preference for defined ring sizes [18] or oligomerization degrees [19]. The idea appears especially attractive for the assembly of peptides with high aggregation tendencies

• reversible dynamic chemistry of specific oligomers are suitable for oligopeptides. Disulfide bonds seem to be the natural choice for the reversible covalent chemistry of peptides, but it appeared to us impossible to prevent both the template and the peptide from homo-oligomer formation. Self-aggregation is

Aggregation behaviour of amphiphilic cyclodextrins: the nucleation stage by atomistic molecular dynamics simulations

• Giuseppina Raffaini,
• Antonino Mazzaglia and
• Fabio Ganazzoli

Beilstein J. Org. Chem. 2015, 11, 2459–2473, doi:10.3762/bjoc.11.267

• report a theoretical study of the aggregation of a few amphiphilic cyclodextrins carrying hydrophobic thioalkyl groups and hydrophilic ethylene glycol moieties at opposite rims, focusing on the initial nucleation stage in an apolar solvent and in water. The study is based on atomistic molecular dynamics

• correlating their structures with the pharmaceutical properties. Keywords: aggregation; amphiphilic cyclodextrins; micelles; molecular dynamics simulations; nanoparticles; self-assembly; Introduction Inclusion complexes with supramolecular structures formed by native or modified cyclodextrins (CDs) are

• recognize cells by exposing receptor-targeting groups on the surface of the nanoassembly [30]. Because of these promising results, we have begun to investigate the aggregation behaviour of an aCD model compound by atomistic computer simulation to clarify the early stages of self-assembly, in particular the

Size-controlled and redox-responsive supramolecular nanoparticles

• Raquel Mejia-Ariza,
• Gavin A. Kronig and
• Jurriaan Huskens

Beilstein J. Org. Chem. 2015, 11, 2388–2399, doi:10.3762/bjoc.11.260

• measurements of the particles in water without salt showed nanoparticles of comparable hydrodynamic diameters (d) for the different Fc/CD ratios. The size for 0% Fc (only CD-PEI) was approx. 70 nm, which is attributed to the fact that the concentration of CD-PEI is above its critical aggregation concentration

• , and values below 20 mV were observed at ionic strengths of 0.1 M and higher, indicating an absence of colloidal stabilization by charge repulsion at high ionic strength. These results demonstrate, as shown before for negatively charged polymers [16], that the aggregation is due to a loss of

• constant as the Fc concentration was increased further (data not shown). Therefore, 2 mM of native CD was added in an attempt to suppress non-specific, hydrophobically driven aggregation at excess Fc moieties. Figure 5a shows, however, a very similar picture, with particle sizes increasing as the Fc

Preparation of Pickering emulsions through interfacial adsorption by soft cyclodextrin nanogels

• Shintaro Kawano,
• Toshiyuki Kida,
• Mitsuru Akashi,
• Hirofumi Sato,
• Motohiro Shizuma and
• Daisuke Ono

Beilstein J. Org. Chem. 2015, 11, 2355–2364, doi:10.3762/bjoc.11.257

• 4.0 × 10−2 wt %, indicating that the DM-β-CD/PDI nanogels have the ability to lower surface tension through the adsorption at the air–water interface. Then, the surface tension reaches a plateau, showing that the nanogels self-aggregate in water. A critical aggregation concentration (CAC) was

• ability to lower surface tension as compared to that of DM-β-CD in the concentration range examined. Moreover, an aqueous solution containing CD nanogels gradually becomes opaque as the CD nanogel concentration increases (>0.1 wt %) possibly due to self-aggregation. Formation of Pickering emulsions The DM

Urethane tetrathiafulvalene derivatives: synthesis, self-assembly and electrochemical properties

• Xiang Sun,
• Guoqiao Lai,
• Zhifang Li,
• Yuwen Ma,
• Xiao Yuan,
• Yongjia Shen and
• Chengyun Wang

Beilstein J. Org. Chem. 2015, 11, 2343–2349, doi:10.3762/bjoc.11.255

• 294 nm and 315 nm (aggregated solid state). This was also observed for T2, which illustrated that π–π interactions and H-aggregation occurred with the increase in concentration [22][23][24]. To further study the driving forces for the self-assembly of T1 and T2, FTIR spectra were also measured (Figure

Self-assemblies of γ-CDs with pentablock copolymers PMA-PPO-PEO-PPO-PMA and endcapping via atom transfer radical polymerization of 2-methacryloyloxyethyl phosphorylcholine

• Jing Lin,
• Tao Kong,
• Lin Ye,
• Ai-ying Zhang and
• Zeng-guo Feng

Beilstein J. Org. Chem. 2015, 11, 2267–2277, doi:10.3762/bjoc.11.247

• . As depicted in Figure 4, the molecular weights were increased with the feed molar ratio of MPC to PEP40M, and all samples exhibited a symmetrical and unimodal GPC curve showing no free γ-CD peak. Although PMA was used as the outer hydrophobic segment to induce the self-aggregation of the pentablock

Synthesis, structure, and mechanical properties of silica nanocomposite polyrotaxane gels

• Kazuaki Kato,
• Daisuke Matsui,
• Koichi Mayumi and
• Kohzo Ito

Beilstein J. Org. Chem. 2015, 11, 2194–2201, doi:10.3762/bjoc.11.238

• transparent, indicating no significant aggregation. Five gels were synthesized in the same way with different initial concentrations of silica nanoparticles. Notably, in the absence of silica nanoparticles, gelation did not occur; only a slight increase of viscosity was observed. This result clearly shows

• limit, indicating that no aggregation is seen even in that q range. Similar SAXS profiles were observed in silica solutions (Figure 5b). Since the correlation distance becomes shorter with the increase of concentration, the distance is thought to be the separation between silica nanoparticles. When we

Cross-metathesis of polynorbornene with polyoctenamer: a kinetic study

• Yulia I. Denisova,
• Maria L. Gringolts,
• Alexander S. Peregudov,
• Liya B. Krentsel,
• Ekaterina A. Litmanovich,
• Arkadiy D. Litmanovich,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2015, 11, 1796–1808, doi:10.3762/bjoc.11.195

• flexible PCOE macromolecules form very compact coils of 4 nm size, which are much smaller than those of rigid PNB chains of nearly the same Mw. At c = 0.03 g/mL is abruptly increased, thus indicating the aggregation of PCOE chains into particles of 25 nm mean size. At even higher concentrations, DLS

• measurements with PCOE are impossible since the solution is not filterable through a 220 nm porosity membrane. Taking into account that the melting temperature of PCOE is about 45 °C, we can relate aggregation in the PCOE solutions at 25 °C to the onset of crystallization. In any case, it makes no sense to

• the crossover concentration in order to study the law of mass action kinetics and restricting aggregation of PCOE chains detected by DLS. We supposed that, apart from the reactions of polymer carbenes formation shown in Scheme 1 and Scheme 2 above and their decay, the cross-metathesis reactions could

Polythiophene and oligothiophene systems modified by TTF electroactive units for organic electronics

• Alexander L. Kanibolotsky,
• Neil J. Findlay and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1749–1766, doi:10.3762/bjoc.11.191

• gate configuration [87]. The hole mobility values calculated in the saturated region were found to be 3.8 × 10−2 and 5.3 × 10−2 cm2 V−1 s−1 for OFETs fabricated via spincoating the semiconductor from solution in chlorobenzene and chloroform, respectively. The strong propensity of 48 to aggregation led

• state spectrum of the chemically synthesised sexithiophene 51; this is evidence of a strong π–π stacking interaction upon aggregation in the solid state. The electrochemistry of compound 51 is similar for both solution and solid state samples, with the main feature being the overlap between the second

• contribution of the quinoidal resonance structure. This effect is only possible for hybrid systems with a TTF unit directly fused to the PT backbone (Scheme 15). Quinqui- and septithiophene TTF bridge systems 54 (n = 1–2) are prone to strong aggregation in solution and, as with 51, a mixture of chloroform with

Star-shaped tetrathiafulvalene oligomers towards the construction of conducting supramolecular assembly

• Masahiko Iyoda and
• Masashi Hasegawa

Beilstein J. Org. Chem. 2015, 11, 1596–1613, doi:10.3762/bjoc.11.175

• accelerate self-aggregation of molecules in solution [6][7][8] and then produce the functional one-dimensional (1D) or two-dimensional (2D) supramolecular structures, which are very important in advanced nanosciences [9][10][11]. For the formation of the nanostructured objects such as fibers, rods, tubes

• cyclic conjugation and the interaction of the two TTF units in the neutral and cationic states, TTF-fused annulenes 33 [69] and radiannulenes 34 and 35 [70] were synthesized using a Sonogashira coupling in moderate yields (Figure 9). The thermodynamic study on the self-aggregation of tris(TTF)annulenes

• indicates that the aggregation of 28, 30, and 31 is an enthalpically driven process that is entropically disfavored (Table 3) [68], although the aggregation of planar macrocyclic belts is both enthalpically and entropically driven [71]. The TTF[18]annulene 30 has smaller ΔH and ΔS values than the TTF[12

Antioxidant potential of curcumin-related compounds studied by chemiluminescence kinetics, chain-breaking efficiencies, scavenging activity (ORAC) and DFT calculations

• Adriana K. Slavova-Kazakova,
• Silvia E. Angelova,
• Timur L. Veprintsev,
• Petko Denev,
• Davide Fabbri,
• Maria Antonietta Dettori,
• Maria Kratchanova,
• Vladimir V. Naumov,
• Aleksei V. Trofimov,
• Rostislav F. Vasil’ev,
• Giovanna Delogu and
• Vessela D. Kancheva

Beilstein J. Org. Chem. 2015, 11, 1398–1411, doi:10.3762/bjoc.11.151

• of favorable contacts with the protein compared to other aromatic compounds and, generally, stability under physiological conditions. It was reported [11] that the dehydrozingerone dimer 6 partially inhibits the aggregation process of alpha synuclein (AS), which is involved as misfolded protein in

Selected synthetic strategies to cyclophanes

• Sambasivarao Kotha,
• Mukesh E. Shirbhate and
• Gopalkrushna T. Waghule

Beilstein J. Org. Chem. 2015, 11, 1274–1331, doi:10.3762/bjoc.11.142

Thiazole-induced rigidification in substituted dithieno-tetrathiafulvalene: the effect of planarisation on charge transport properties

• Rupert G. D. Taylor,
• Joseph Cameron,
• Iain A. Wright,
• Neil Thomson,
• Olena Avramchenko,
• Alexander L. Kanibolotsky,
• Anto R. Inigo,
• Tell Tuttle and
• Peter J. Skabara

Beilstein J. Org. Chem. 2015, 11, 1148–1154, doi:10.3762/bjoc.11.129

• resolved but there is a non-resolved peak caused by overlap of the cathodic peaks on the reverse scan. Compound 2 appears to show a first oxidation wave at 0.09 V, however, this is an artefact due to a minor degree of aggregation induced by π–π stacking between some of the molecules. This is followed by

Synthesis of photoresponsive cholesterol-based azobenzene organogels: dependence on different spacer lengths

• Yuchun Ren,
• Bin Wang and
• Xiuqing Zhang

Beilstein J. Org. Chem. 2015, 11, 1089–1095, doi:10.3762/bjoc.11.122

• to gel phase transition under visible irradiation. The corresponding visual images are shown in Figure 3. Scanning electron microscopy studies To obtain a visual insight into the morphology of the aggregation mode, the typical structures of the xerogels prepared by the freeze-drying of the three gels

• ethanol, isopropanol and 1-butanol. Based on the results of SEM, IR and XRD, it demonstrated that the solvents, intermolecular H-bonding, and van der Waals interaction affected the aggregation mode and morphology of gels. These results can be applied in fields of design and development of novel

A hybrid electron donor comprising cyclopentadithiophene and dithiafulvenyl for dye-sensitized solar cells

• Gleb Sorohhov,
• Chenyi Yi,
• Michael Grätzel,
• Silvio Decurtins and
• Shi-Xia Liu

Beilstein J. Org. Chem. 2015, 11, 1052–1059, doi:10.3762/bjoc.11.118

• other hand, the presence of side chains on both DTF and CPDT moieties could prevent dye aggregation and thus retard charge recombination. Herein, we describe the preparation, characterization and the electronic properties of two new organic dyes as well as their application in DSSCs. Results and

• full π-conjugation increases the propensity of dye aggregation on the TiO2 surface, leading to a decrease of the electron-injection yield, too. Overall, the dyes show a relatively poor DSSC performance compared to the analogous systems reported in the literature so far [18][19], which is mainly due to

• substantial charge recombination losses during the electron-injection process, very probably caused by self-aggregation on the TiO2 surface and fast back-electron transfer upon photoexcitation. Conclusion In summary, we have synthesized two new organic photosensitizers featured with a DTF–CPDT hybrid as an

Terminal lipophilization of a unique DNA dodecamer by various nucleolipid headgroups: Their incorporation into artificial lipid bilayers and hydrodynamic properties

• Emma Werz and
• Helmut Rosemeyer

Beilstein J. Org. Chem. 2015, 11, 913–929, doi:10.3762/bjoc.11.103

• experimental conditions with respect to concentration and temperature, we do not observe a strong aggregation tendency – a finding corroborated by the agreement between the calculated and measured hydrodynamic properties. Any aggregates are obviously not bound within the lipid bilayer, but only in free