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

• Department of Chemistry and Biochemistry, University of Windsor, 401 Sunset Avenue, Windsor, N9B 3P4, Canada 10.3762/bjoc.14.146 Abstract Host–guest complexes of C-hexyl-2-bromoresorcinarene (BrC6) with twelve potential aromatic N-oxide guests were studied using single crystal X-ray diffraction analysis and

• formation of host–guest complexes [40][55], while the less competitive chloroform tends to enhance capsular assemblies [55]. Only one set of resonances from the 1H NMR of the receptor BrC6 in all the solvents and solvent mixtures is observed, thus confirming a symmetrical crown conformation in solution

β-Hydroxy sulfides and their syntheses

• Mokgethwa B. Marakalala,
• Edwin M. Mmutlane and
• Henok H. Kinfe

Beilstein J. Org. Chem. 2018, 14, 1668–1692, doi:10.3762/bjoc.14.143

• host–guest complexes by non-covalent bonding [64]. This mode of catalysis is similar to the way enzymes mediate biochemical reactions [64]. The use of water as a solvent and the non-toxicity of the cyclodextrin catalyst make the method attractive. This method, like the previously reported protocols, is

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

• follow a parabolic rather than a linear free energy relationship. A closer look at four representative crystal structures suggested that the parabolic free energy relationship may be caused through influencing the major interactions in the host–guest complexes by tuning the weak C–H∙∙∙O hydrogen bonds

• understand the importance of conformational adaptivity in biomolecular recognition and even design stimuli-responsive materials by harnessing this large amplitude of conformational changes. X-ray single crystal structure of ZB4 and the host–guest complexes. a) ZB4, b) 2+@ZB4-IV, c) 3+@ZB4-IV, d) 10+@ZB4-I

A three-armed cryptand with triazine and pyridine units: synthesis, structure and complexation with polycyclic aromatic compounds

• Claudia Lar,
• Adrian Woiczechowski-Pop,
• Attila Bende,
• Ioana Georgeta Grosu,
• Natalia Miklášová,
• Elena Bogdan,
• Niculina Daniela Hădade,
• Anamaria Terec and
• Ion Grosu

Beilstein J. Org. Chem. 2018, 14, 1370–1377, doi:10.3762/bjoc.14.115

• , the resonances continuously changed positions during variation of the host:guest ratios thus proving that the formation of the host–guest complexes is a fast, dynamic process. The changes of the chemical shift for the signal belonging to the more deshielded signal of the p-phenylene units (doublet at

• is larger than the distance (3.15 Å) determined for the triazine dimer [41]. As next step, the polycyclic aromatic hydrocarbons anthracene and pyrene were intercalated between the caps of the cryptand. The optimized geometry structures of these host–guest complexes were obtained using the same method

• of the cryptand–anthracene (a) and cryptand–pyrene (b) host–guest complexes. The equilibrium geometry structure of the cryptand 2–1,5-dihydroxynaphthalene host–guest complex. The inclusion dynamics of the anthracene in the cavity of the cryptand for different constrained distances (blue < green < red

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

• 1:1 host–guest complexes are present in the samples. Otherwise, deviations from the expected trend give evidence of the formation of higher order aggregates. In order to study the interaction between AmCDs and Alg, a stock alginate solution 25 mN was first prepared as follows. The proper amount of

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

• charge status of the host and the structure of the guest. Thus, the use of the polarimetric method was thoroughly revisited, in order to keep into account the occurrence of multiple equilibria. Our data indicate that the stability of the host–guest complexes is affected by an interplay between Coulomb

• : calix[4]resorcinarene; host–guest complexes; p-nitroanilines; polarimetry; supramolecular chemistry; Introduction During the last decades calix[n]arenes and calix[n]resorcinarenes (CAs) have emerged as versatile supramolecular host systems for various applications [1][2][3][4][5], spanning from sensors

Exploring mechanochemistry to turn organic bio-relevant molecules into metal-organic frameworks: a short review

• Vânia André,
• Sílvia Quaresma,
• João Luís Ferreira da Silva and
• M. Teresa Duarte

Beilstein J. Org. Chem. 2017, 13, 2416–2427, doi:10.3762/bjoc.13.239

• field of supramolecular chemistry [27][28][29], for solvent-free preparation of co-crystals, and adducts [30][31][32][33][34][35][36][37][38], polymorphs [12], supramolecular aggregates [4][30][39][40][41][42], host–guest complexes [5][43][44][45], metal-organic frameworks (MOFs) [8][28][44][46][47][48

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

• ; pemetrexed; supramolecular chemistry; Introduction Herein, supramolecular host–guest complexes of the potent folic acid inhibitor pemetrexed (PTX, Figure 1a) with native cyclodextrins (α-, β- and γ-CDs, Figure 1b) in the gas phase (MS), in solution (NMR, UV–vis) and in the solid state (Raman, FTIR–ATR) were

• the guest molecule is located inside the CD cavity. The present study serves two purposes. The first is studying of the process of formation of the host–guest complexes of all three native CDs with PTX, an antifolate exhibiting considerable toxicity and their detailed characterization in the gas phase

• Raman bands of the native CD in comparison to the bands of the guest molecule [29]. In contrary, the spectrum of the host–guest complexes, where due to molecular interactions some changes in Raman spectra would be observed (shifting or decreasing of the peak intensity or broadening of characteristic

Complexation of molecular clips containing fragments of diphenylglycoluril and benzocrown ethers with paraquat and its derivatives

• Leonid S. Kikot',
• Catherine Yu. Kulygina,
• Alexander Yu. Lyapunov,
• Svetlana V. Shishkina,
• Roman I. Zubatyuk,
• Tatiana Yu. Bogaschenko and
• Tatiana I. Kirichenko

Beilstein J. Org. Chem. 2017, 13, 2056–2067, doi:10.3762/bjoc.13.203

• complexes with paraquat (7), the host–guest complexes 2@8 and 3@8 are stabilized by π–π stacking, C–H···O and C–H···π interactions. So far as the structures of these complexes are very similar the main attention will be paid to some differences only. The presence of the terminal hydroxy groups creates the

p-tert-Butylthiacalix[4]arenes functionalized by N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments: synthesis and binding of anionic guests

• Alena A. Vavilova and
• Ivan I. Stoikov

Beilstein J. Org. Chem. 2017, 13, 1940–1949, doi:10.3762/bjoc.13.188

• thiacalix[4]arenes 2, 7–10 (Figure 1) [26][42] with N-(4’-nitrophenyl)acetamide and N,N-diethylacetamide fragments was of interest. Initially, molecular modeling of the host–guest complexes of the above-mentioned thiacalix[4]arenes 2, 3, 5–10 with a number of single-charged anions (F−, Cl−, Br−, I−, CH3CO2

• correlates with an increase in the energy change in the formation of the host–guest complexes in the case of the macrocycles 3, 7. For the compounds 2, 6, 9, the efficiency of complexation is close. Conclusion New mono-, 1,2-di- and tetrasubstituted at the lower rim p-tert-butylthiacalix[4]arenes containing

β-Cyclodextrin- and adamantyl-substituted poly(acrylate) self-assembling aqueous networks designed for controlled complexation and release of small molecules

• Liang Yan,
• Duc-Truc Pham,
• Philip Clements,
• Stephen F. Lincoln,
• Jie Wang,
• Xuhong Guo and
• Christopher J. Easton

Beilstein J. Org. Chem. 2017, 13, 1879–1892, doi:10.3762/bjoc.13.183

• complexed states, λmax, and the derived K11 (Table 2) were determined by best-fitting an algorithm derived from Equations 4–6 to the titration absorbance data using a nonlinear least-squares program, HypSpec [51][52]. The largest and smallest K11 characterize the β-CD–EO and β-CD–MR host–guest complexes

Structure–efficiency relationships of cyclodextrin scavengers in the hydrolytic degradation of organophosphorus compounds

• Sophie Letort,
• Michaël Bosco,
• Benedetta Cornelio,
• Frédérique Brégier,
• Sébastien Daulon,
• Géraldine Gouhier and
• François Estour

Beilstein J. Org. Chem. 2017, 13, 417–427, doi:10.3762/bjoc.13.45

• hydrolyze the organophosphorus (OP) compounds under physiological conditions. In this context, cyclodextrins (CD) constitute attractive starting materials because, due to the inclusion properties of their internal cavity, they can form host–guest complexes in aqueous media by weak interactions with small

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

• cationic form were individually tested with six different P-CDs at cyclodextrin concentrations of 5, 10 and 20 mM. All substrates, except for 14, have aromatic rings in their structures. Previous studies [21][31][32] and observations made herein with the P-CDs indicate that host–guest complexes through

Computational methods in drug discovery

• Sumudu P. Leelananda and
• Steffen Lindert

Beilstein J. Org. Chem. 2016, 12, 2694–2718, doi:10.3762/bjoc.12.267

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

• direct assemblies, the structural definition and kinetic stability of 2:1 host–guest complexes might be low. We therefore wanted to introduce a bias by using very rigid guests. We were therefore grateful to discover that a range of steroids, from as small as estradiol to as large as cholesterol formed

• its exterior and a dry, water-free nano-space for harboring a guest or guests. The range of guests that form 2:1(2) host–guest complexes is illustrated by the examples in Figure 7. As expected, if a co-solvent is added then these complexes are broken down. Thus, screening of eight different co

• competitor is primarily left in solution and undergoes hydrolysis. Ideally therefore, none of the stored ester undergoes hydrolysis, before all of the second reacts. We discovered that the esters all formed kinetically stable 2:1 host–guest complexes and bound with the following relative affinity to the host

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

• the interaction of S4TdR and CDs were determined according to the modified Benesi–Hildebrand (B–H) relation (Equation 1) [9] assuming the formation of host–guest complexes with stoichiometry of 1:1. In Equation 1, IG represents the cathodic current intensity of the guest molecule, in absence of CDs

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

• complexation and, indeed, multiple guests could be measured at once [14]. The HPLC method of determining complexation ΔΗ° values was extended by Vincent Kwan to hydrogen bonding host–guest complexes [15]. Molecular tweezers that complex adenine and analysis of binding interactions The idea of incorporating

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

• more effective chain growth inhibitor as it decreased the aggregate size from 700 nm to 400 nm. Potassium cinnamate (CioOK) as a competitive guest molecule was able to completely displace the cinnamyl part of 3-O-Cin-α-CD from the adjacent CD cavity which resulted in decomposition of the host–guest

• complexes. As a result a significant decrease in the Dh of the aggregates (from 700 nm to 1.6 nm) was observed (Figure 10 and Figure 11). The observed differences between the efficiency of the chain growth inhibition of AdCOOK and CioOK can be explained by the different size of the two competitive guest

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

• complexes hydrophobic guest species to form host–guest complexes, or inclusion compounds. The host–guest complexes formed by cyclodextrins and their hydrophobic guests, which range from small molecules to polymer substituents and sections of polymer chains, have been widely studied and utilized as building

• substituents rendering a solution viscous by forming host–guest complexes with individual hydrophobic substituents and thereby lower solution viscosity [41][42][43][44]. This process may be reversed by adding competing hydrophobes which complex cyclodextrins more strongly than the hydrophobic substituents to

• 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

Release of β-galactosidase from poloxamine/α-cyclodextrin hydrogels

• César A. Estévez,
• José Ramón Isasi,
• Eneko Larrañeta and
• Itziar Vélaz

Beilstein J. Org. Chem. 2014, 10, 3127–3135, doi:10.3762/bjoc.10.330

• are able to form host–guest complexes by the inclusion of hydrophobic molecules. Cyclodextrins also act as hosts in the formation of inclusion compounds with polymer chains through non-covalent interactions [10]. For instance, incorporation of 5% α-CD transforms dilute Tetronic solutions into gels

Binding mode and free energy prediction of fisetin/β-cyclodextrin inclusion complexes

• Bodee Nutho,
• Wasinee Khuntawee,
• Chompoonut Rungnim,
• Piamsook Pongsawasdi,
• Peter Wolschann,
• Alfred Karpfen,
• Nawee Kungwan and
• Thanyada Rungrotmongkol

Beilstein J. Org. Chem. 2014, 10, 2789–2799, doi:10.3762/bjoc.10.296

• applications, β-CD has been mostly used as a drug carrier, stabilizer and additive by the formation of host–guest complexes with increased solubility and consequently better bioavailability of low water soluble organic compounds (i.e., drugs) [20][21][22][23]. The inclusion complex can also improve ligand

Towards the sequence-specific multivalent molecular recognition of cyclodextrin oligomers

• Michael Kurlemann and
• Bart Jan Ravoo

Beilstein J. Org. Chem. 2014, 10, 2428–2440, doi:10.3762/bjoc.10.253

• towards α- and β-CD was investigated by ITC experiments. The structures of the host–guest complexes were elucidated by NMR spectroscopy. The 1-adamantane-functionalized serine 17 shows complexation of α- and β-CD, forming 1:1 complexes. In both cases the adamantane moiety binds into the CD cavity, which

• for the interaction with α-CD, the EM cannot be increased that easy. Here the linkers of the guest and the host moieties have a crucial influence on the structure of the divalent molecules and the host–guest complexes before the intramolecular complexation [1]. Changes in the linkers’ structures can

• the structures of the host–guest complexes were recorded on an Agilent DD2 600 (Agilent Technologies, Santa Clara, California, USA). Samples were prepared by dissolving 10 equivalents of CD in the corresponding volume of a 1 mM stock solution of the guest molecules in D2O. Analysis of the data was

Derivatives of the triaminoguanidinium ion, 3. Multiple N-functionalization of the triaminoguanidinium ion with isocyanates and isothiocyanates

• Jan Szabo,
• Kerstin Karger,
• Nicolas Bucher and
• Gerhard Maas

Beilstein J. Org. Chem. 2014, 10, 2255–2262, doi:10.3762/bjoc.10.234

• transformations using heterocumulenes as reagents. Due to their particular molecular shape and the presence of hydrogen-bond donor and acceptor groups, the obtained 1,2,3-tris(ureido)guanidinium salts 7 and the derived neutral guanidine 8 may become of interest as host components in host–guest complexes, for

Macrocyclic bis(ureas) as ligands for anion complexation

• Claudia Kretschmer,
• Gertrud Dittmann and
• Johannes Beck

Beilstein J. Org. Chem. 2014, 10, 1834–1839, doi:10.3762/bjoc.10.193

• formed (Figure 4). To ensure the composition of the host–guest complexes Job plots were used. The function molar fraction vs the product of molar fraction multiplied by the shift change Δδ allows for the determination of the molar fractions of host and guest. From the maximum of the extrapolated curve

Molecular recognition of isomeric protonated amino acid esters monitored by ESI-mass spectrometry

• Andrea Liesenfeld and
• Arne Lützen

Beilstein J. Org. Chem. 2014, 10, 825–831, doi:10.3762/bjoc.10.78

• quasi-isomer is performed to reveal the relative affinity of a receptor towards the different isomers. In this way, the mass spectrometric analysis easily allows direct identification of the individual host–guest complexes. This is usually more complicated with other techniques such as, e.g., NMR

• spectroscopy because it is more difficult to assign the signals to the individual host–guest complexes and the analysis might be additionally hindered or even be impossible due to severe signal overlapping. In our case, we used the methyl groups of the ester function as the mass label by employing either the

• analysed by ESI-mass spectrometry (Figure 4). The intensity ratios of the signals of the host–guest complexes can then be used to conclude which guest is bound stronger since the mass difference is large enough to allow an individual detection but also small enough not to cause any problems due to mass