Dynamic light scattering studies of the effects of salts on the diffusivity of cationic and anionic cavitands

• Anthony Wishard and
• Bruce C. Gibb

Beilstein J. Org. Chem. 2018, 14, 2212–2219, doi:10.3762/bjoc.14.195

• , Figure S3), which revealed only trace amounts of host aggregation (≈5%). Furthermore, even at 100 mM salt concentration, 1H NMR spectroscopy failed to show any significant association of Cs+ to the crown of four carboxylates. Thus, although this crown is the most obvious potential cation binding site, we

• anion pairing in solution; that small (large) anions preferentially bind with small (large) cations, whereas large size differences lead to weak association [30]. Thus, this law of matching water affinities (LMWA) suggests that in aqueous solution CsI is more strongly ion-paired than LiI. The observed

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• TTFs. However, also the type of substituent on the TTF moiety plays a role in terms of weak secondary binding interactions such as hydrogen bonds [63]. For example TTF 5 which is substituted by ethylene glycol chains displays a high association constant of Ka = 50,000 M−1 in acetonitrile. Additionally

• -cationic form since the association energy of the donor–acceptor complex must be overcome. After oxidation, the radical-cation 1●+ is expelled from host 3 by repulsive Coulombic forces. If 1●+ gets further oxidized to the π-electron-poor dication 12+, the π-electron-rich macrocycle 8 can now encapsulate

• = 6,300 M−1) which is embedded in an axle molecule with two azide residues. The second station, the dihydroxynaphthalene moiety (green), displays a lower association constant of Ka = 5,800 M−1. The pseudorotaxane precursor was end-capped by a double copper-catalyzed azide–alkyne click reaction in CH2Cl2

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• spectrum of the mixture of 1 and 2+ in CDCl3 remained unchanged after 48 h at 298 K, thus showing that the system had reached the equilibrium condition. At this point, an apparent association constant of 6.2 ± 0.3 × 103 M–1 was calculated by quantitative 1H NMR analysis (tetrachloroethane as internal

• studies. Also in this case, after equilibration at 298 K for 24 h, this preference was reversed in favour of the 3+1cone atropoisomer, with a 3+1cone/3+11,2,3-alt ratio of 8/1. From the equilibrium mixture, an apparent association constant of 9.3 ± 0.4 × 102 M−1 was calculated by quantitative 1H NMR

• analysis (tetrachloroethane as internal standard) for the formation of 3+1cone pseudorotaxane. In a similar way, an apparent association constant of 120 ± 15 M−1 was found for 3+11,2,3-alt pseudorotaxane. As evidenced for axle 2+, also in this case, after the initial formation of the kinetic pseudorotaxane

A switchable [2]rotaxane with two active alkenyl groups

• Xiu-Li Zheng,
• Rong-Rong Tao,
• Rui-Rui Gu,
• Wen-Zhi Wang and
• Da-Hui Qu

Beilstein J. Org. Chem. 2018, 14, 2074–2081, doi:10.3762/bjoc.14.181

• a ΔδH3 = 0.51 ppm due to the association with the DB24C8 macrocycle through hydrogen bonding. All the evidences reveal that the functionalized macrocycle migrated from the DBA recognition site to the amide station when an external base was added to the solution of rotaxane R1. Then, 3 equiv

An amphiphilic pseudo[1]catenane: neutral guest-induced clouding point change

• Tomoki Ogoshi,
• Tomohiro Akutsu and
• Tada-aki Yamagishi

Beilstein J. Org. Chem. 2018, 14, 1937–1943, doi:10.3762/bjoc.14.167

• by 1,4-dicyanobutane. The association constant between the pseudo[1]catenane structure 3 and 1,4-dicyanobutane estimated by 1H NMR at 25 °C was 13.9 M−1 (Supporting Information File 1, Figure S6), which is remarkably lower than the association constant between 1 and 1,4-dicyanobutane (4.6 × 104 M−1

• , 149.6, 149.4 129.0, 128.6, 128.3, 124.3, 115.7, 115.0, 71.9, 70.8, 70.7, 70.6, 70.3, 68.4, 68.1, 67.8, 67.6, 59.0, 29.7, 29.0, 28.8, 28.5, 27.3, 24.5 ppm; HRMS–ESI (m/z): [M + 2Na]2+ calcd for C109H170N6Na2O34, 1076.5777; found, 1076.5635. Determination of association constants. In a similar manner as

• described in [6], association constants of the host–guest complexes were determined. In the host–guest complex of 1,4-dicyanobutane with 3 in D2O, the chemical exchange between the complexed and uncomplexed species was slow on the NMR timescale. Thus, the 1H NMR spectra of mixtures of 3 with 1,4

Synthesis of 9-arylalkynyl- and 9-aryl-substituted benzo[b]quinolizinium derivatives by Palladium-mediated cross-coupling reactions

• Siva Sankar Murthy Bandaru,
• Darinka Dzubiel,
• Heiko Ihmels,
• Mohebodin Karbasiyoun,
• Mohamed M. A. Mahmoud and
• Carola Schulzke

Beilstein J. Org. Chem. 2018, 14, 1871–1884, doi:10.3762/bjoc.14.161

• ligands; fluorescence; heterocycles; Pd-mediated couling reactions; quinolizinium; Introduction Polycyclic cationic hetarenes are a paradigm of DNA-binding ligands whose association with the nucleic acid may affect the biological activities of the DNA [1][2][3][4]. For example, a DNA-bound heterocyclic

• titration. The fluorescence intensity of the derivatives 2a and 2d is significantly quenched by the addition of DNA, respectively (Figure 8 and Figure 9). This observation usually indicates a photoinduced electron transfer between the excited molecules and the DNA bases [69]. By contrast, the association of

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

• aminoethyl substituent shows comparable binding to etidronate. At present, the reason for this behavior remains unclear. Overall, the strong binding of 9 BPs with GC5A with association constants in the μM to nM range is suitable for the following sensing study. By executing IDA based on the GC5A·Fl reporter

• a guanidinium cation. Schematic illustration of the binding between BPs and GC5A and the operating IDA principle of fluorescence “switch-on” sensing of BPs by the GC5A·Fl reporter pair. The chemical structures of the selected BP drugs. Association constants (Ka) of BPs and GC5A determined according

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

Design, synthesis and structure of novel G-2 melamine-based dendrimers incorporating 4-(n-octyloxy)aniline as a peripheral unit

• Cristina Morar,
• Pedro Lameiras,
• Attila Bende,
• Gabriel Katona,
• Emese Gál and
• Mircea Darabantu

Beilstein J. Org. Chem. 2018, 14, 1704–1722, doi:10.3762/bjoc.14.145

• latter. Due to their overall lower symmetry in comparison with trimesic acid, tripodal aminophenoxy-acids-based N-substituted melamines C2 and C3 exhibited multiple (3–4) carboxyl νC=O stretching absorptions, in agreement with their different degrees of H-bond association, i.e., dimers (1742 and 1709 cm

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

• −. NMR titrations and isothermal titration microcalorimetry (ITC) were then performed to obtain the association constants. For small guests such as 1+, 2+, 6+–9+, NMR titration experiments with ZB4 have been performed due to the fast equilibrium of the free and ZB4-complexed guests on the NMR time scale

• the results are shown in Table 1. Generally, ZB4 shows weaker binding affinities to these guests than TA4 does with the same counterions. For example, ZB4 and cation 3+, with a binding constant of 5.4 × 104 M−1, was the best guest among the studied ones. However, the corresponding association constant

• electronic properties of substituents present in the guests and their binding affinities with TA4, indicating that the binding affinities are affected by substituents through a field/inductive effect [34]. However, this is again quite different for ZB4. The association constants of ZB4 to these guests were

Two new 2-alkylquinolones, inhibitory to the fish skin ulcer pathogen Tenacibaculum maritimum, produced by a rhizobacterium of the genus Burkholderia sp.

• Dandan Li,
• Naoya Oku,
• Atsumi Hasada,
• Masafumi Shimizu and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2018, 14, 1446–1451, doi:10.3762/bjoc.14.122

• association with animals or plants as pathogens or symbionts and exhibit a variety of catabolic and metabolic activities [1][7]. One hundred ten secondary metabolites have been reported from Burkholderia (data retrieved from the Dictionary of Natural Products, as of March 20, 2018). However, it is likely that

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 theoretical one. Global non-linear regression analysis of the 1H NMR titration data indicated the formation of 1:1 stoichiometric complexes. The association constants for the complexation of 2 with anthracene, pyrene and 1,5-dihydroxynaphthalene are 472.81 M−1 ± 4.9882, 55.22 M−1 ± 2.7771 and

• experimental (the order of the association constants) and theoretical (the magnitude of the binding energies) results, the intermolecular interaction energies were recomputed considering solvent effects induced by the DMSO solvent environment. Accordingly, the intermolecular interaction energies for the

• –guest interaction in the case of the dihydroxylated guest leads to a weaker host–guest interaction and consequently to a lower association constant. This may explain the different results obtained from the experimental and theoretical data. Indeed, the recalculation including the influence of the

[3 + 2]-Cycloaddition reaction of sydnones with alkynes

• Veronika Hladíková,
• Jiří Váňa and
• Jiří Hanusek

Beilstein J. Org. Chem. 2018, 14, 1317–1348, doi:10.3762/bjoc.14.113

• -phenylsydnone and DMAD was first studied by Huisgen and Gotthardt [54] in p-cymene at 90–110 °C. They found the cycloaddition to be overall second order and its activation entropy ΔS≠ = −130 J·mol−1·K−1 showed association character of the rate-limiting step with a relatively tight transition state. Moreover

An overview of recent advances in duplex DNA recognition by small molecules

• Sayantan Bhaduri,
• Nihar Ranjan and
• Dev P. Arya

Beilstein J. Org. Chem. 2018, 14, 1051–1086, doi:10.3762/bjoc.14.93

• study their solution-phase self-association characteristics and DNA molecular-recognition properties [17]. The authors showed a measurable difference in solution-phase self-assembly character with enhanced DNA association characteristics by replacing the formamide head group in thiazotropsin A with

• ). This has been attributed to strong self-association (dimerization) in an antiparallel, head-to-tail orientation in aqueous solution during complex formation with duplex DNA oligomers verified via NOE experiments [61]. They further reported several structurally diverse MGBs, derived from distamycin, in

• shown in the Figure 6. In conclusion, the authors reported that β-substituted polyamides weakens the binding affinity of these conjugates with cognate DNA and drastically influence the binding kinetics such as association and dissociation rates in a position- and number-dependent manner. The authors, in

Phosphodiester models for cleavage of nucleic acids

• Satu Mikkola,
• Tuomas Lönnberg and
• Harri Lönnberg

Beilstein J. Org. Chem. 2018, 14, 803–837, doi:10.3762/bjoc.14.68

An uracil-linked hydroxyflavone probe for the recognition of ATP

• Márton Bojtár,
• Péter Zoltán Janzsó-Berend,
• Dávid Mester,
• Dóra Hessz,
• Mihály Kállay,
• Miklós Kubinyi and
• István Bitter

Beilstein J. Org. Chem. 2018, 14, 747–755, doi:10.3762/bjoc.14.63

• -5’-triphosphate, GTP) and the strong solvation of the chemosensor and the analyte in aqueous media, reducing the association constant of their complex, and through that the sensitivity of the sensor [31][32]. The molecular recognition of nucleotides in most chemosensors is achieved by charged

• polarized dimethylamino group of DMHF and the negative charges of ATP. The interaction of DMHF with nucleotides and a computer aided simulation on the geometry of DMHF∙ATP complexes in vacuo was also reported. A recent study by the same authors describe further flavones with various association constants

• interactions, which prompted us towards the synthesis of UHF by click chemistry. Fluorescence spectroscopy revealed a selective complexation with ATP with an association constant of around 2∙104 M−1 and a ratiometric response in the excitation spectrum. Results and Discussion Structure and calculations Based

Stimuli-responsive oligonucleotides in prodrug-based approaches for gene silencing

• Françoise Debart,
• Christelle Dupouy and
• Jean-Jacques Vasseur

Beilstein J. Org. Chem. 2018, 14, 436–469, doi:10.3762/bjoc.14.32

Fluorogenic PNA probes

• Tirayut Vilaivan

Beilstein J. Org. Chem. 2018, 14, 253–281, doi:10.3762/bjoc.14.17

• allowed direct detection of double stranded (ds)DNA targets after simple denaturation due to the ability of PNA to bind more strongly to DNA and so effectively compete with the DNA re-association. Another research group from Japan also reported a similar stem-loop non-chimeric PNA beacon carrying two

5-Aminopyrazole as precursor in design and synthesis of fused pyrazoloazines

• Ranjana Aggarwal and
• Suresh Kumar

Beilstein J. Org. Chem. 2018, 14, 203–242, doi:10.3762/bjoc.14.15

The use of 4,4,4-trifluorothreonine to stabilize extended peptide structures and mimic β-strands

• Yaochun Xu,
• Isabelle Correia,
• Tap Ha-Duong,
• Nadjib Kihal,
• Jean-Louis Soulier,
• Julia Kaffy,
• Benoît Crousse,
• Olivier Lequin and
• Sandrine Ongeri

Beilstein J. Org. Chem. 2017, 13, 2842–2853, doi:10.3762/bjoc.13.276

• periodicity may reflect transient intermolecular β-strand contacts involving hydrogen bonding through Val2 and Val4 residues (Figure S16, Supporting Information File 1). However, no long-range HN/HN or Hα/Hα ROEs could be detected in the 8 pentapeptides, indicating that transient intermolecular association

• observed for the central residue upon replacement of Ser by the β-branched Thr residue and the incorporation of a trifluoromethyl group in Thr or allo-Thr further increases the β-propensity of these residues. The presence of self-association involving intermolecular β-sheet formation was not detectable

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation and chlorination. Part 2: Use of CF₃SO₂Cl

• Hélène Chachignon,
• Hélène Guyon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2800–2818, doi:10.3762/bjoc.13.273

• single-electron transfer (SET) between CF3SO2Cl and the association CuBr/chiral phosphoric acid. In the process, SO2 and HCl were released, but the latter was scavenged by Ag2CO3, minimising its impact on the reaction process by notably avoiding hydroamination side reactions. The trifluoromethyl radical

CF₃SO₂X (X = Na, Cl) as reagents for trifluoromethylation, trifluoromethylsulfenyl-, -sulfinyl- and -sulfonylation. Part 1: Use of CF₃SO₂Na

• Hélène Guyon,
• Hélène Chachignon and
• Dominique Cahard

Beilstein J. Org. Chem. 2017, 13, 2764–2799, doi:10.3762/bjoc.13.272

• , judicious installation of CF3 group(s) in catalysts or ligands is an effective tool to tune their reactivity and selectivity in synthesis. As a pharmacophore, CF3 substantially improves the catabolic stability, lipophilicity, and transport rate. In association with chalcogens (OCF3, SCF3, SeCF3), the CF3

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

• may reasonably hypothesize the occurrence of a loose ion-pairing external association between the cationic pendant groups of the host and the anionic guest (Figure 5). Binding abilities of AmCDs towards Alg Further assessment of a possible out-of-cavity interaction for AmCDs was achieved by studying

• rotation Θ of AmCDs CD1–3 vs pH. Trends of the molar optical rotation Θ of AmCDs vs χH+. Polarimetric data trends for the inclusion of 4 in CD1 at different pH values. Possible association of AmCDs with guests 2–4. Polarimetric data trends for the CD1–Alg interaction (with buffer). nr Values for the AmCD

An efficient synthesis of 1,6-anhydro-N-acetylmuramic acid from N-acetylglucosamine

• Matthew B. Calvert,
• Christoph Mayer and
• Alexander Titz

Beilstein J. Org. Chem. 2017, 13, 2631–2636, doi:10.3762/bjoc.13.261

• : NMR spectra. Acknowledgements The authors thank Dr. Josef Zapp (Saarland University) for recording NMR spectra and Daniel Sauer (Helmholtz Institute for Pharmaceutical Research Saarland, HIPS) for HRMS measurements. We are grateful to the Helmholtz Association (grant no. VH-NG-934) for financial

Synthesis and supramolecular properties of regioisomers of mononaphthylallyl derivatives of γ-cyclodextrin

• Markéta Bláhová,
• Sergey K. Filippov,
• Lubomír Kováčik,
• Jiří Horský,
• Simona Hybelbauerová,
• Zdenka Syrová,
• Tomáš Křížek and
• Jindřich Jindřich

Beilstein J. Org. Chem. 2017, 13, 2509–2520, doi:10.3762/bjoc.13.248

• the shape of peaks, but also in the value of the chemical shifts. For both regioisomers the concentration dependence of chemical shifts in aromatic and allyl areas indicates intermolecular association such as inclusion of the naphthylallyl moiety into the cavity of γ-CD or π stacking of naphthyls. The

• as a ditopic monomer of the AB type with groups A and B undergoing an association of 1:1. However, a number of alternate or competing interactions may occur, as mentioned above, γ-CD is known to form also inclusion complexes of 2:1 stoichiometry and formation of cyclic supramolecular structures my