Reversible photoswitching of the DNA-binding properties of styrylquinolizinium derivatives through photochromic [2 + 2] cycloaddition and cycloreversion

• Sarah Kölsch,
• Heiko Ihmels,
• Jochen Mattay,
• Norbert Sewald and
• Brian O. Patrick

Beilstein J. Org. Chem. 2020, 16, 111–124, doi:10.3762/bjoc.16.13

• methoxy-substituted styrylquinolizinium derivatives form the corresponding syn head-to-tail cyclobutanes in a selective [2 + 2] photocycloaddition, as revealed by X-ray diffraction analysis of the reaction products. These photodimers bind to DNA only weakly by outside-edge association, but they release

• ; photodimerization; photoswitches; Introduction The association of DNA-targeting drugs with nucleic acids [1][2][3][4][5][6][7][8] is considered one of the essential properties that determine their biological activity [9]. Specifically, a ligand may occupy particular binding sites of DNA or induce significant

• solution at pH 7.0 (Figure 2). During the photometric titrations, the initial absorption maxima continuously decreased and new, bathochromically shifted absorption maxima arose at 464 nm (3a), 404 nm (3b), 399 nm (3c), and 378 nm (3d), respectively (Figure 2), which clearly indicated the association of

The interaction between cucurbit[8]uril and baicalein and the effect on baicalein properties

• Xiaodong Zhang,
• Jun Xie,
• Zhiling Xu,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2020, 16, 71–77, doi:10.3762/bjoc.16.9

• progressively higher absorbance with a slight red shift as the molar ratio of NQ[8]/NBALE increased. The absorbance (Figure 4A–C) vs molar ratio of the host Q[8] and guest (NQ[8]/NBALE) was fitted to a 1:1 binding model to afford the association constants (K) [2.15 × 107 L·mol−1 (10 mol·L−1 HCl), 3.59 × 107

Photocontrolled DNA minor groove interactions of imidazole/pyrrole polyamides

• Sabrina Müller,
• Jannik Paulus,
• Jochen Mattay,
• Heiko Ihmels,
• Veronica I. Dodero and
• Norbert Sewald

Beilstein J. Org. Chem. 2020, 16, 60–70, doi:10.3762/bjoc.16.8

• derivatives was proven by CD titration experiments. The resulting induced circular dichroism (ICD) bands of the bound ligands, together with the photometric determination of the dsDNA melting temperature, revealed a significant stabilization of the DNA upon association with the ligand. The (Z)-azobenzene

Light-controllable dithienylethene-modified cyclic peptides: photoswitching the in vivo toxicity in zebrafish embryos

• Sergii Afonin,
• Oleg Babii,
• Aline Reuter,
• Volker Middel,
• Masanari Takamiya,
• Uwe Strähle,
• Igor V. Komarov and
• Anne S. Ulrich

Beilstein J. Org. Chem. 2020, 16, 39–49, doi:10.3762/bjoc.16.6

• to their original design in [30]. Acknowledgements We thank Dr. Wadhwani (KIT, Karlsruhe) for access to the peptide synthesis facility. Funding Financial support was provided by Helmholtz Association (Germany) via the program “BioInterfaces in Technology and Medicine” (BIF-TM). SA, OB, IVK, and ASU

Chemical synthesis of tripeptide thioesters for the biotechnological incorporation into the myxobacterial secondary metabolite argyrin via mutasynthesis

• David C. B. Siebert,
• Roman Sommer,
• Domen Pogorevc,
• Michael Hoffmann,
• Silke C. Wenzel,
• Rolf Müller and
• Alexander Titz

Beilstein J. Org. Chem. 2019, 15, 2922–2929, doi:10.3762/bjoc.15.286

• Helmholtz Association (HGF, grant no. VH-NG-934), the European Research Council (ERC StG, grant no SWEETBULLETS) and the German Centre for Infection Research (DZIF) is acknowledged. Author Contributions Statement D.C.B.S. and R.S. designed and performed peptide synthesis. D.P. and S.C.W. designed and

Preparation of anthracene-based tetraperimidine hexafluorophosphate and selective recognition of chromium(III) ions

• Qing-Xiang Liu,
• Feng Yang,
• Zhi-Xiang Zhao,
• Shao-Cong Yu and
• Yue Ding

Beilstein J. Org. Chem. 2019, 15, 2847–2855, doi:10.3762/bjoc.15.278

• detection (LOD) was calculated to be 2.33⋅10−7 M (Supporting Information File 1, Figure S3). This value is analogous to the lowest corresponding value that has been reported in the literature (9.40⋅10−7–5.55⋅10−6 M) [44][45][46]. The association constant KSV was calculated to be 6.6⋅104 M−1 (R = 0.998) for

Fluorinated maleimide-substituted porphyrins and chlorins: synthesis and characterization

• Valentina A. Ol’shevskaya,
• Elena G. Kononova and
• Andrei V. Zaitsev

Beilstein J. Org. Chem. 2019, 15, 2704–2709, doi:10.3762/bjoc.15.263

• selectively, covalently in high yields with no requirement for prior activation of reactants [29] and thus strengthen the association of a drug molecule with the cell surface. It is important to mention that Kitagishi and co-workers [30] showed that the maleimide-appended porphyrin/cyclodextrine complex was

Sugar-derived oxazolone pseudotetrapeptide as γ-turn inducer and anion-selective transporter

• Sachin S. Burade,
• Sushil V. Pawar,
• Tanmoy Saha,
• Navanath Kumbhar,
• Amol S. Kotmale,
• Manzoor Ahmad,
• Pinaki Talukdar and
• Dilip D. Dhavale

Beilstein J. Org. Chem. 2019, 15, 2419–2427, doi:10.3762/bjoc.15.234

• was recorded that showed a higher Δδ/ΔT value of 6.2 × 10−3 ppm/K for NH(I) indicating its involvement in weak intramolecular H-bonding. For NH(II) the lower Δδ/ΔT value of 3.7 × 10−3 ppm/K supported its association in strong intramolecular hydrogen bonding with C=O leading to the γ-turn formation

1,2,3-Triazolium macrocycles in supramolecular chemistry

• Mastaneh Safarnejad Shad,
• Pulikkal Veettil Santhini and
• Wim Dehaen

Beilstein J. Org. Chem. 2019, 15, 2142–2155, doi:10.3762/bjoc.15.211

• changes in the CDCl3 solution of anionic species (Figure 3). The receptor 1a has shown remarkable affinity toward fluoride ion with an association constant of 560 M−1 followed by Cl− > Br− > I− > CH3COO− with the affinity range of 5.6 × 102 to 6.0 × 101 M−1 but no binding was observed with the H2PO4− ion

• synthesized the novel tetra-1,2,3-triazolium zinc porphyrin cage 3 (Figure 4) and have probed its characteristics by using UV–visible spectroscopy, determining the association constants for complex formation in 5% water/acetone. This receptor has shown affinity toward all of the halide ions and especially

• association constant of macrocycle 3 in the more competitive 15% water/acetone medium, still demonstrating a high binding affinity for sulfate anion (Ka = 2.5 × 105 M−1) while the cage 3 did not show any binding toward the other tested anions in the more aqueous solvent mixture. 2.3. Redox-active 1,2,3

Multiple threading of a triple-calix[6]arene host

• Veronica Iuliano,
• Roberta Ciao,
• Emanuele Vignola,
• Carmen Talotta,
• Patrizia Iannece,
• Margherita De Rosa,
• Annunziata Soriente,
• Carmine Gaeta and
• Placido Neri

Beilstein J. Org. Chem. 2019, 15, 2092–2104, doi:10.3762/bjoc.15.207

• -tetrachloroethane as internal standard, an apparent association constant of 1.01 ± 0.03 × 104 M−1 was calculated for the 7+6 pseudo[2]rotaxane. When 1 equiv of 7+·TFPB− salt was added to the 1:1 mixture of 6 and 7+·TFPB− in CDCl3 (Figure 4c), then, in addition to the benzylic resonances of the 7+6 pseudo[2]rotaxane

• − δcomplexed = 2.69), −0.88 (Δδ = 2.58), −0.57 (Δδ = 1.94), −0.40 (Δδ = 1.32), and 0.64 ppm (Δδ = 2.37) ppm attributable, respectively, to the β, γ, δ, ε, and α H-atoms of the pentyl chain of axle 4+ inside the calix-cavity of 6 (Figure 7). An apparent association constant of 1.20 ± 0.02 × 104 M–1 was

• (Figure 10) of this mixture confirmed the formation of the 8+6 pseudo[2]rotaxane by the presence of a molecular ion peak at 3408.3230 m/z (calcd 3408.3122 for C233H306NO18+). Finally, an apparent association constant of 5.70 ± 0.03 × 102 M−1 was calculated by 1H qNMR analysis for the single-threaded 8+6

Morphology-tunable and pH-responsive supramolecular self-assemblies based on AB₂-type host–guest-conjugated amphiphilic molecules for controlled drug delivery

• Yang Bai,
• Cai-ping Liu,
• Di Chen,
• Long-hai Zhuo,
• Huai-tian Bu and
• Wei Tian

Beilstein J. Org. Chem. 2019, 15, 1925–1932, doi:10.3762/bjoc.15.188

• -induced association and disassociation of β-CD/BM complexes, these supramolecular self-assemblies with adjustable morphology and size were obtained. The fan-shaped supramolecular self-assemblies were first obtained based on the host–guest interaction between β-CD and BM, then further dissociated under

Tautomerism as primary signaling mechanism in metal sensing: the case of amide group

• Vera Deneva,
• Georgi Dobrikov,
• Aurelien Crochet,
• Daniela Nedeltcheva,
• Katharina M. Fromm and
• Liudmil Antonov

Beilstein J. Org. Chem. 2019, 15, 1898–1906, doi:10.3762/bjoc.15.185

• , the formation of the seven-membered hydrogen-bonding ring in 6E cannot compete with the flexibility of the system in the case of the intermolecular association. Compared to another tautomeric C=O containing ionophore, recently developed [13], it seems that the existence of a carbonyl group leads in

• association plays a role in some solvents as shown by the experimental results. The calculations predict that the complexation with alkali earth metal ions could lead to a full shift of the tautomeric equilibrium towards the keto tautomer, which was finally observed in solution. The formed 1:1 complexes

Complexation of 2,6-helic[6]arene and its derivatives with 1,1′-dimethyl-4,4′-bipyridinium salts and protonated 4,4'-bipyridinium salts: an acid–base controllable complexation

• Jing Li,
• Qiang Shi,
• Ying Han and
• Chuan-Feng Chen

Beilstein J. Org. Chem. 2019, 15, 1795–1804, doi:10.3762/bjoc.15.173

• derivatives for the additional multiple hydrogen bonding interactions between the hosts and the guests, which were evidenced by 1H NMR titrations, X-ray crystal structures and DFT calculations. Moreover, it was also found that the association constants (Ka) of the complexes could be significantly enhanced

• –S22). Furthermore, job plots showed that throughout 1:1 host–guest complexes are formed (Supporting Information File 1, Figures S56–S88). To gain quantitative insight into the complexation between the hosts and the guests, we carried out 1H NMR titrations and calculated the association constants Ka by

• the nonlinear curve-fitting method [40]. As shown in Table 1, compared with its derivatives, the unsubstituted host helic[6]arene H1 showed the strongest complexation with all guests tested. The association constant (Ka) of complex H1·G1 was calculated to be (6.76 ± 1.02) × 103 M−1, while the Ka of H2

A heteroditopic macrocycle as organocatalytic nanoreactor for pyrroloacridinone synthesis in water

• Piyali Sarkar,
• Sayan Sarkar and
• Pradyut Ghosh

Beilstein J. Org. Chem. 2019, 15, 1505–1514, doi:10.3762/bjoc.15.152

• Piyali Sarkar Sayan Sarkar Pradyut Ghosh School of Chemical Sciences, Indian Association for the Cultivation of Science, 2A & 2B Raja S.C Mullick Road, Kolkata-700032, India 10.3762/bjoc.15.152 Abstract A heteroditopic macrocycle is reported as an efficient organocatalytic nanoreactor for the

• observed an ESIMS peak at m/z 679.32 corresponding to [BATA-MC + 1a + H]+ (Supporting Information File 1, Figure S2) which supported the association of the macrocycle with isatin. Hence, further condensation between enaminoketone and isatin provides the intermediate B. The isatin moiety also has π-stacking

2,3-Dibutoxynaphthalene-based tetralactam macrocycles for recognizing precious metal chloride complexes

• Li-Li Wang,
• Yi-Kuan Tu,
• Huan Yao and
• Wei Jiang

Beilstein J. Org. Chem. 2019, 15, 1460–1467, doi:10.3762/bjoc.15.146

• ] or (TBA)2[PdCl4]. Binding constants of 1 to the precious metal chloride complexes were determined in CDCl3 by 1H NMR titrations (Figures S9−S14, Supporting Information File 1). The data are listed in Table 1. TBA[AuCl4] shows the highest association constant (Ka) with a value of 265 ± 33 M−1. The Ka

• mass spectrum (Figure S15, Supporting Information File 1). Therefore, the association constant for (TBA)2[PdCl4] may, in fact, be caused by the mixture of (TBA)2[PdCl4], TBACl, and (TBA)2[Pd2Cl6]. Tetralactam macrocycles are known to bind chloride ions as well [4][40]. Indeed, 1 is able to bind TBACl

• tetralactam macrocycles [41]. These binding affinities are lower than those of a positively-charged macrocycle [42], but are comparable or superior when compared to other tetralactam macrocycles. With respect to the association constants to TBA[AuCl4] and TBACl, 1 is comparable to the tetralactam macrocycles

Reaction of oxiranes with cyclodextrins under high-energy ball-milling conditions

• László Jicsinszky,
• Federica Calsolaro,
• Katia Martina,
• Fabio Bucciol,
• Maela Manzoli and
• Giancarlo Cravotto

Beilstein J. Org. Chem. 2019, 15, 1448–1459, doi:10.3762/bjoc.15.145

• of β-CDP showed linear concentration dependency, as seen in Figure 5. It is known that, although γ-CD is able to form complexes with MO (they are less stable than those of β-CD), the prepared insoluble γ-CDP has few affinity towards MO. It can be also assumed that it is only the association rate that

Complexation of a guanidinium-modified calixarene with diverse dyes and investigation of the corresponding photophysical response

• Yu-Ying Wang,
• Yong Kong,
• Zhe Zheng,
• Wen-Chao Geng,
• Zi-Yi Zhao,
• Hongwei Sun and
• Dong-Sheng Guo

Beilstein J. Org. Chem. 2019, 15, 1394–1406, doi:10.3762/bjoc.15.139

• representative candidate of luminescent transition-metal complexes. We determined the association constants of the GC5A–dye complexes by fluorescence titration and discuss the complexation-induced photophysical changes. In addition, a comparison of the complexation behavior of GC5A with that of other macrocycles

• according to the Job's plot. The association constant (Ka) was well fitted as 5.0 × 106 M−1 (Table 1) by a 1:1 binding model according to both fluorescence titration and UV–vis titration. The drastically altered fluorescence signal upon complexation, Ifree/Ibound, is calculated as a factor of 37. EY, RB

Formation of an unexpected 3,3-diphenyl-3H-indazole through a facile intramolecular [2 + 3] cycloaddition of the diazo intermediate

• Andrew T. King,
• Hugh G. Hiscocks,
• Lidia Matesic,
• Mohan Bhadbhade,
• Roger Bishop and
• Alison T. Ung

Beilstein J. Org. Chem. 2019, 15, 1347–1354, doi:10.3762/bjoc.15.134

• stepladder association of eight molecules (5b, lower). Crystallographic colour code: C–H···N purple), C–H···H–C (light blue), inversion centre (orange sphere), and incomplete contacts (red). Part of a hydrocarbon tape along a formed by a combination of alternating linear and cyclic C–H···H–C close contacts

Host–guest interactions between p-sulfonatocalix[4]arene and p-sulfonatothiacalix[4]arene and group IA, IIA and f-block metal cations: a DFT/SMD study

• Valya K. Nikolova,
• Cristina V. Kirkova,
• Silvia E. Angelova and
• Todor M. Dudev

Beilstein J. Org. Chem. 2019, 15, 1321–1330, doi:10.3762/bjoc.15.131

• anchoring points for the positively charged guests. Cation–π interactions between the monoatomic cations and p-sulfonatocalix[4]arene in water are supposed (but not proven) to take part in the inclusion complex formation [31]. Mendes et al. have carried out molecular dynamics (MD) simulations of association

• upon binding has been noted [31]. A model of hydrated, by an average number of 10 water molecules, La3+ cation has already been used by Mendes et al. in the MD simulations of p-sulfonatocalix[4]arene association with rare-earth metal cations and organic cations in aqueous solutions [32]. The effect of

Enantioselective Diels–Alder reaction of anthracene by chiral tritylium catalysis

• Qichao Zhang,
• Jian Lv and
• Sanzhong Luo

Beilstein J. Org. Chem. 2019, 15, 1304–1312, doi:10.3762/bjoc.15.129

• -coordinated phosphonate anion with balanced association ability with tritylium ions provided a new opportunity in pursuing chiral ion pair-type carbocation catalysis. The resulted asymmetric tritylium catalysis has enabled the so-far challenging Diels–Alder reactions of unsubstituted anthracene with good

Molecular recognition using tetralactam macrocycles with parallel aromatic sidewalls

• Dong-Hao Li and
• Bradley D. Smith

Beilstein J. Org. Chem. 2019, 15, 1086–1095, doi:10.3762/bjoc.15.105

• preorganized structures that favor high affinity and shape-selective association of guest molecules or ions. Usually, it is the solvent that determines which non-covalent interactions are the most important for strong association. Polar interactions are often dominant in weakly polar organic solvents, and thus

• the structure of an effective macrocyclic host must include polar functional groups. In water, association is often driven by the hydrophobic effect which means the interior cavity of an effective macrocyclic host should have sections with non-polar surfaces [3]. A macrocyclic host molecule with an

• factors is reversed; hydrogen bonding is relatively weak and strong guest association occurs when hydrophobic sections of a complementary guest are able to contact the hydrophobic interior surfaces of the two aromatic sidewalls [26]. The first macrocycle system in Scheme 1 to be studied in detail was

Stereo- and regioselective hydroboration of 1-exo-methylene pyranoses: discovery of aryltriazolylmethyl C-galactopyranosides as selective galectin-1 inhibitors

• Alexander Dahlqvist,
• Axel Furevi,
• Niklas Warlin,
• Hakon Leffler and
• Ulf J. Nilsson

Beilstein J. Org. Chem. 2019, 15, 1046–1060, doi:10.3762/bjoc.15.102

• uptake and breakdown, respectively. The association of galectins to cell signaling and adhesion gives them roles in several different pathological processes, such as pulmonary fibrosis [6][10], pathological lymphangiogenesis [11], inflammation [12] and cancer [13], with galectin inhibitors demonstrated

New terpenoids from the fermentation broth of the edible mushroom Cyclocybe aegerita

• Frank Surup,
• Florian Hennicke,
• Nadine Sella,
• Maria Stroot,
• Steffen Bernecker,
• Sebastian Pfütze,
• Marc Stadler and
• Martin Rühl

Beilstein J. Org. Chem. 2019, 15, 1000–1007, doi:10.3762/bjoc.15.98

• Frank Surup Florian Hennicke Nadine Sella Maria Stroot Steffen Bernecker Sebastian Pfutze Marc Stadler Martin Ruhl Microbial Drugs, Helmholtz Centre for Infection Research GmbH (HZI), Inhoffenstraße 7, 38124 Braunschweig, Germany German Centre for Infection Research Association (DZIF), Partner

Fabrication of supramolecular cyclodextrin–fullerene nonwovens by electrospinning

• Hiroaki Yoshida,
• Ken Kikuta and
• Toshiyuki Kida

Beilstein J. Org. Chem. 2019, 15, 89–95, doi:10.3762/bjoc.15.10

• formation process [4][5]. In 2006, Long et al. reported a unique and innovative approach to produce fibers via electrospinning [6]. They focused on the association behavior of surfactant molecules as a function of the solution concentration and demonstrated that phospholipids (lecithins) in nonaqueous media

• , simply by increasing the feed of C60 up to 40 mg/mL can control the equilibrium (Figure 2d). However, such a highly concentrated C60 solution is unstable and the solution changes to dark brown after a few days. In the electrospinning of small molecules, controlling intermolecular association in solution

• is essential. Association is predicted from the relationship of the solution viscosity and concentration [6][9][11]. As reported previously, the increased rate of viscosity with the concentration in γ-CD/HFIP solution clearly becomes larger at 10–15 w/v %, indicating intermolecular associations of γ

Lectins of Mycobacterium tuberculosis – rarely studied proteins

• Katharina Kolbe,
• Sri Kumar Veleti,
• Norbert Reiling and
• Thisbe K. Lindhorst

Beilstein J. Org. Chem. 2019, 15, 1–15, doi:10.3762/bjoc.15.1

• number of detected potential lectins, which ranged from one to six per strain, and their phylogenetic association to established lectin families strongly varied depending on the mycobacterial species in question [77]. These results are consistent with the varying carbohydrate-binding characteristics

• ][84][85], which have been previously studied in detail (see below). We subsequently discuss the association of the nine putative Mtb lectins identified by Singh et al. and Abhinav et al. with established lectin families [77][78], such as agglutinin-like sequences (ALS), mannose-sensitive hemagglutinin

• shown that MTP is associated with Mtb aggregation and biofilm formation in vitro [116]. The importance of these interactions in patients, however, has yet to be confirmed, as the association of mycobacterial biofilms with bacterial pathogenesis has not yet been conclusively shown in vivo. Besides