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

• 1H NMR spectroscopy. In the solid state, of the nine obtained X-ray crystal structures, eight were consistent with the formation of BrC6-N-oxide endo complexes. The lone exception was from the association between 4-phenylpyridine N-oxide and BrC6, in that case the host forms a self-inclusion complex

• ) contacts between guest C3 hydrogens and the host carbon/hydroxy oxygens, respectively. From our experience, the lack of π-acidic aromatic protons in guest 10 usually results in exo complexes [36][37][39]. To our surprise, 10+BrC6 forms a self-inclusion complex of BrC6 by itself as shown in Figure 2g, the

• property usually preferred by resorcinarenes when solvate and guest molecules are absent inside the cavity. Note that the self-inclusion complex of BrC6 has exo methanol solvent hydrogen bonds to host hydroxy groups. This can possibly be explained by the longer lower-rim hexyl chains providing enough

Mechanochemistry of nucleosides, nucleotides and related materials

• Olga Eguaogie,
• Joseph S. Vyle,
• Patrick F. Conlon,
• Manuela A. Gîlea and
• Yipei Liang

Beilstein J. Org. Chem. 2018, 14, 955–970, doi:10.3762/bjoc.14.81

• : specifically, solid solutions, cocrystals, polymorph transitions, carbon nanotube dissolution and inclusion complex formation. Keywords: DNA; green chemistry; mechanochemistry; nucleoside; nucleotide; Introduction Several definitions of mechanochemistry have been attempted since Ostwald included it as one of

Crystal structure of the inclusion complex of cholesterol in β-cyclodextrin and molecular dynamics studies

• Elias Christoforides,
• Andreas Papaioannou and
• Kostas Bethanis

Beilstein J. Org. Chem. 2018, 14, 838–848, doi:10.3762/bjoc.14.69

• of cholesterol in β-CD. The inclusion complex crystallizes in the triclinic space group P1 forming head-to-head dimers which are stacked along the c-axis. One well-defined cholesterol molecule ‘axially’ encapsulated inside the β-CD dimer and 22 water molecules that stabilize the complexes in the

• characterization of the cholesterol/β-CD inclusion complex [22], its binding affinity [23][24][25], the inclusion mode of the complex [26] and its dynamic behavior through MD simulations [27][28][29] but its crystal structure is absent. In this work, the structure of CHL/β-CD is determined by X-ray crystallography

• and its geometrical features are examined thoroughly. In order to examine the stability of the crystallographically determined model excluding the crystal contacts observed in the crystalline state, MD simulations of the inclusion complex in aqueous environment were performed. The starting set of

Binding abilities of polyaminocyclodextrins: polarimetric investigations and biological assays

• Marco Russo,
• Daniele La Corte,
• Annalisa Pisciotta,
• Serena Riela,
• Rosa Alduina and
• Paolo Lo Meo

Beilstein J. Org. Chem. 2017, 13, 2751–2763, doi:10.3762/bjoc.13.271

• possible occurrence of two different behaviours (Figure 4). With the neutral guest 1 at any pH and with the anionic guests 2–4 at the highest pH values, data trends account for the exclusive formation of a 1:1 host–guest inclusion complex. By contrast, with guests 2–4 at the lowest pH values, i.e

• the ideal host axis. This, in turn, suggests that the polarized guest molecule penetrates more and more deeply into the CD cavity on increasing the overall positive charge, owing to the occurrence of stronger dipolar interactions. Therefore, the inclusion complex becomes stiffer and stiffer, with a

Structural diversity in the host–guest complexes of the antifolate pemetrexed with native cyclodextrins: gas phase, solution and solid state studies

• Magdalena Ceborska,
• Magdalena Zimnicka,
• Aneta Aniela Kowalska,
• Kajetan Dąbrowa and
• Barbara Repeć

Beilstein J. Org. Chem. 2017, 13, 2252–2263, doi:10.3762/bjoc.13.222

• various sizes (4.7–8.3 Å) into which distinct compounds may enter and form inclusion complexes, an ability that is thoroughly used by the pharmaceutical industry for the formation of drug delivery systems [1][2][3][4][5]. The formation of an inclusion complex often results in a favorable change of

• methods – FTIR–ATR and Raman were used for describing the way of PTX-CD interactions. The IR spectroscopy in the region characteristic for δ-HOH bending of water molecules attached to CDs (1600–1700 cm−1) is usually employed for tracking of the inclusion complex formation, however, Raman spectra of this

• energies, are these resulting from covalent bond cleavages [19]. The loosely bonded CDs/PTX complexes therefore correspond to a pseudorotaxane inclusion complex in which PTX is threaded through the CD’s cavity or other type of exclusion aggregate. To distinguish between these two types of complexes their

Solid-state studies and antioxidant properties of the γ-cyclodextrin·fisetin inclusion compound

• Joana M. Pais,
• Maria João Barroca,
• Maria Paula M. Marques,
• Filipe A. Almeida Paz and
• Susana S. Braga

Beilstein J. Org. Chem. 2017, 13, 2138–2145, doi:10.3762/bjoc.13.212

• evaluation of the antioxidant activity of the inclusion compound by the DPPH assay, and its comparison with that of pure fisetin. Preparation and characterization of γ-CD·fisetin The preparation of the γ-CD·fisetin inclusion complex was carried out by co-dissolution, followed by either co-crystallization or

• between the diffraction envelope of the recrystallized γ-CD·fisetin and the diffractogram calculated from the atomic coordinates of a model inclusion complex, γ-CD–12-crown-4 ether (trace (d) in Figure 1) [31]. Such a match, according to Caira’s systematization of crystalline CD inclusion compounds [30

• inclusion complex of fisetin with γ-CD was successfully achieved by co-dissolution followed by co-lyophilization. The material obtained is an amorphous solid powder that can be converted into a microcrystalline powder by rehydration without any dissociation of the inclusion complex. The method can thus be

Influence of the milling parameters on the nucleophilic substitution reaction of activated β-cyclodextrins

• László Jicsinszky,
• Kata Tuza,
• Giancarlo Cravotto,
• Andrea Porcheddu,
• Francesco Delogu and
• Evelina Colacino

Beilstein J. Org. Chem. 2017, 13, 1893–1899, doi:10.3762/bjoc.13.184

• findings lend support to the idea that mechanical activation can induce chemical reactivity [29] and selectivity [30] which is different to that observed in solution, which can be further complicated by the inclusion complex formation property of cyclodextrins. How exactly the milling parameters influence

Molecular recognition of N-acetyltryptophan enantiomers by β-cyclodextrin

• Spyros D. Chatziefthimiou,
• Mario Inclán,
• Petros Giastas,
• Athanasios Papakyriakou,
• Konstantina Yannakopoulou and
• Irene M. Mavridis

Beilstein J. Org. Chem. 2017, 13, 1572–1582, doi:10.3762/bjoc.13.157

• percentage cannot be excluded. X-ray crystallography studies In the crystalline state, the structure of the inclusion complex of L-NAcTrp in β-CD comprises dimers. The asymmetric unit of the complex contains two crystallographically independent β-CD hosts (A and B) forming a dimer (Figure 2), in which two

• directions (Figure 2 and Figure 3). These differences maximize the strong interactions between major guests C and D (Figure 3, Table 1). Numerous trials to crystallize the inclusion complex of β-CD with D-NAcTrp have failed to give anything but hydrated β-CD crystals [29], as described in detail in the

Interactions between shape-persistent macromolecules as probed by AFM

• Johanna Blass,
• Jessica Brunke,
• Franziska Emmerich,
• Cédric Przybylski,
• Vasil M. Garamus,
• Artem Feoktystov,
• Roland Bennewitz,
• Gerhard Wenz and
• Marcel Albrecht

Beilstein J. Org. Chem. 2017, 13, 938–951, doi:10.3762/bjoc.13.95

• end groups were prepared starting from diacetylene-modified cyclodextrin monomers by a combined Glaser coupling/click chemistry approach. Structural perfection of the neutral CD polymers and inclusion complex formation with ditopic and monotopic guest molecules were proven by MALDI–TOF and UV–vis

The effect of cyclodextrin complexation on the solubility and photostability of nerolidol as pure compound and as main constituent of cabreuva essential oil

• Joyce Azzi,
• Pierre-Edouard Danjou,
• David Landy,
• Steven Ruellan,
• Lizette Auezova,
• Hélène Greige-Gerges and
• Sophie Fourmentin

Beilstein J. Org. Chem. 2017, 13, 835–844, doi:10.3762/bjoc.13.84

• solid complexes was assessed by HPLC. The structural characterization of CD/trans-Ner inclusion complex was then conducted by NMR spectroscopy followed by molecular modelling studies. The effect of encapsulation on the Ner photostability was also carried out over time under UVB irradiation. AL-type

• -Ner isomer leading to a more stable inclusion complex [16]. An exception is observed for γ-CD, where cis-Ner is better encapsulated than trans-Ner, owing to the larger cavity of this CD. Phase-solubility studies also allow the determination of the complexation efficiency (CE) permitting to evaluate

• (mixture of cis and trans isomers) and HP-β-CD was also evaluated by a UV-visible competition method with methyl orange (MO) as a competitor [23]. Before starting the competition experiment, the Kf value of the HP-β-CD/MO inclusion complex was determined by direct titration; the data were consistent with

Inclusion complexes of β-cyclodextrin with tricyclic drugs: an X-ray diffraction, NMR and molecular dynamics study

• Franca Castiglione,
• Fabio Ganazzoli,
• Luciana Malpezzi,
• Andrea Mele,
• Walter Panzeri and
• Giuseppina Raffaini

Beilstein J. Org. Chem. 2017, 13, 714–719, doi:10.3762/bjoc.13.70

• complex geometry in solution and in the solid state was carried out, while the only similation study of this complex was very limited both in scope and in the adopted methodology [6]. In addition, to the best of our knowledge no study was ever performed on the inclusion complex of the strictly related

• single bond. The lack of disorder in the C9–C10 segment suggests that complexation constrains 2 in a single conformation in the solid state. The MD simulations led to the formation of a 1:1 inclusion complex of β-CD with molecules 1 and 2 both in vacuo and in explicit water. In both cases, the complex

• finally optimized up to an energy gradient lower than 4 × 10−3 kJ mol−1 Å−1. The simulation protocol closely followed the strategy proposed by some of us for modeling the inclusion complex formation without any a priori assumption about its possible geometry [17][18][19][20][21]. Thus, the optimized

Fluorescent carbon dots from mono- and polysaccharides: synthesis, properties and applications

• Stephen Hill and
• M. Carmen Galan

Beilstein J. Org. Chem. 2017, 13, 675–693, doi:10.3762/bjoc.13.67

• ) when compared to 36% release at pH 7 and 27% at pH 12. In order to improve the drug delivery profile of the complex, the authors developed a β-cyclodextrin/tetracycline (β-TC) host–guest inclusion complex, which allows a second “barrier” of release. The pre-formulated β-TC complex was loaded onto the

Novel β-cyclodextrin–eosin conjugates

• Gábor Benkovics,
• Damien Afonso,
• András Darcsi,
• Szabolcs Béni,
• Sabrina Conoci,
• Éva Fenyvesi,
• Lajos Szente,
• Milo Malanga and
• Salvatore Sortino

Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52

• systems in combined phototherapies. This approach has recently led to self-assembled systems based on a porphyrin–β-CD conjugate and a tailored nitric oxide photoreleaser forming a strong inclusion complex with the β-CD cavity [9]. This supramolecular nanoassembly simultaneously releases cytotoxic 1O2 and

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

• . Isosbestic points were only maintained during titration at pH 5. The analysis of the binding isotherms obtained from photometric titrations at pH 5 revealed a 1:1 stoichiometry of 2-CB[7] inclusion complex and a corresponding binding constant of Kb = 1.8 × 104 M−1 (Supporting Information File 1, Figure S5

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

• formation of a host–guest inclusion complex – does not occur, confirming the situation already described by HR-MAS NMR data for the same system in the gel state [9] and outlining a different scenario on passing from monomeric CD, capable to form well characterized inclusion complexes with IbuH [29][30][31

• result is that the guest molecules are mainly confined in the pores formed by the polycondensation process rather than forming a genuine inclusion complex with the single CD units. From a practical point of view, our class of polymerized cyclodextrins can be conveniently exploited as sorbent or scaffold

• by exploiting the pores of the polymer network to encapsulate the guest molecules. However, it should be stressed that CD nanosponges similar to ours and prepared by using citric acid as cross-linker, showed a different behaviour towards ibuprofen: the authors provided evidence of inclusion complex

Versatile synthesis of end-reactive polyrotaxanes applicable to fabrication of supramolecular biomaterials

• Atsushi Tamura,
• Asato Tonegawa,
• Yoshinori Arisaka and
• Nobuhiko Yui

Beilstein J. Org. Chem. 2016, 12, 2883–2892, doi:10.3762/bjoc.12.287

• functional PRXs and can be applied to the fabrication of PRX-based supramolecular biomaterials. Keywords: azide group; biomaterials; click chemistry; cyclodextrin; polyrotaxane; Introduction Polyrotaxanes (PRXs) are a class of interlocked polymers that consist of an inclusion complex of cyclodextrins (CDs

• the terminals of the axle polymers have an attractive designs for the fabrication of biomaterials, because the terminal azide or alkynyl groups in the PRXs can be utilized for the modification of other polymer chains and functional molecules. In general, PRXs comprising an inclusion complex of a

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

• pollutant of emerging concern (EP), was protected by CMBCD-P against the photocatalytic degradation showing that inclusion complex formation can result in opposite effects depending on the structure of the host–guest complex. Keywords: carboxymethyl β-cyclodextrin polymer; colloid stability; ibuprofen

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

• -CD < α-CD. This behavior was attributed to the large cavity of γ-CD which is able to incorporate both alkyl chains of DHPC simultaneously. In contrast, the formation of a 1:2 inclusion complex with α-CD is easier than with γ-CD. These findings are corroborated by Fauvelle and co-workers who reported

• inclusion complex because of the driving force of complexation: hydrophobic interaction. Despite there is no information on the binding constant observed for the inclusion of cholesterol in γ-CD, the cavity internal diameter of the β-CD and its derivatives perfectly matches the size of the sterol molecules

• , respectively). Therefore, the pentapeptide conformation affects the stability of the pentapeptide/β-CD inclusion complex. In contrast, the pentapeptide/α-CD inclusion complex was not affected by the oligopeptide conformation (27, 20, and 20 M−1 for free Try, YIGSR, and YGGFL, respectively). The same year

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

• in water was significantly low, leading to the formation of precipitates. β-CD-CTA forms a self-inclusion complex or a supramolecular dimer complex, which was characterized using 2D ROESY NMR (Supporting Information File 1, Figure S4). We focused on the polymerization activity of α-CD-CTA because the

• the growing polymer chain, and exploring its function mimicking a biological molecular clamp. Preparation scheme of α-CD-CTA. Crystal structure of α-CD with N,N-dimethylacrylamide (DMA). (a) The structure of an 1:1 inclusion complex between α-CD and DMA. One of the disordered pattern of DMA is shown

• . DMA molecules outside the α-CD, hydrogen atoms, and water molecules are omitted for clarity. Colors of the atoms are based on CPK coloring. DMA, space-filling model; CD, stick model. (b) A schematic diagram of the inclusion complex of α-CD/DMA. Time-conversion curves (a), kinetic plots (b) and plots

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

• interactions are established, the diffusion of the inclusion complex from the bulk of the solution to the electrode surface is much slower than that of the guest itself leading at least to the observed current decrease (Figure 3 and Figure 4B) under our experimental conditions. As reported in [36], a decrease

• the reduction of the involved groups in the inclusion complex need less activation energy. On the other hand, when TRIMEB CD was considered, while the cathodic peak potential can be considered constant, the current intensity decreases after the first CD addition then it remains constant (Figure 3E

Optimized methods for preparation of 6^I-(ω-sulfanyl-alkylene-sulfanyl)-β-cyclodextrin derivatives

• Eva Bednářová,
• Simona Hybelbauerová and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2016, 12, 349–352, doi:10.3762/bjoc.12.38

• inclusion complex with β-CD [22], i.e., a suitable accessibility of the cavity should be kept, and further inclusion complexes could be formed with the guests. Strict inert conditions are also required for the next synthetic step – preparation of compounds 5. The air had to be removed from the reaction

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

• by reacting β-CD with tosyl imidazole (TsIm) [15]. Great advantages, in terms of yields, reaction times and product purity, were obtained by using a cavitating tube (40 min, 19.2 kHz, 20 W, yield: 55%). Thanks to the fast US-assisted inclusion complex formation between β-CD and TsIm reaction times

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

• technics [43]. Despite the pronounced solubility changes consistent with complex formation, little variations in the UV spectra, combined with the guest’s small chemical shifts observed in 1H NMR experiments (0.01–0.06 ppm), suggest the formation of external complexes rather than an inclusion complex

• . However the inclusion complex formation was strengthen by molecular modeling studies with the aromatic group included into the cavity. Finally, DSC curves showed a first endothermic portion starting at 225 °C, typical of a melting process, and a second sharp exothermic decomposition peak, proving the

• formation of the inclusion complex. Thus, on the basis of these last results, the formation of an internal inclusion complex was favored by the authors. In 2013, Cruickshank reported the X-ray crystal structures of the heptakis(2,3,6-trimethyl)-β-cyclodextrin (TRIMEB)–fenthion complex (complex with 2

Thermal and oxidative stability of Atlantic salmon oil (Salmo salar L.) and complexation with β-cyclodextrin

• Daniel I. Hădărugă,
• Mustafa Ünlüsayin,
• Alexandra T. Gruia,
• Cristina Birău (Mitroi),
• Gerlinde Rusu and
• Nicoleta G. Hădărugă

Beilstein J. Org. Chem. 2016, 12, 179–191, doi:10.3762/bjoc.12.20

• support the conclusion of formation of the β-CD/FA glyceride inclusion complex by means of water behavior. Hydration water is easier released from the β-CD/ASO complexes obtained at a 3:1 molar ratio. Both DSC and KFT analyses demonstrate this finding with a lower peak temperature and lower “strongly

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

• how two units of Kagan’s ether provide the necessary C-shaped geometry [29]. Then, Harmata himself synthesized tweezer 18, reporting its solution binding studies and a beautiful solid-state inclusion complex with trinitrobenzene [30]. This series of molecular tweezers was reviewed in 2004 [31]. A