¹⁹F NMR as a tool in chemical biology

• Diana Gimenez,
• Aoife Phelan,
• Cormac D. Murphy and
• Steven L. Cobb

Beilstein J. Org. Chem. 2021, 17, 293–318, doi:10.3762/bjoc.17.28

• important element in the broader space of chemical biology [2]. Many commercial and industrial compounds are fluorinated, including refrigerants, degreasers, drugs, pesticides and anti-stick materials, and consequently there is a high degree of interaction between fluorinated compounds and nature [3

• estrogen receptor (ER) co-activator peptides and enabled the sensitive detection of their protein–peptide interaction inhibition by the ER antagonist tamoxifen [20]. Significantly, different secondary structure conformational preferences were also found among the diastereomers of perfluoro-tert

• enabled the direct calculation of most of the ligand binding constants. The superior capacity of 19F NMR to monitor binding events was also noted by Richards et al., when studying the interaction of human protein disulphide isomerase (hPDI) to Δ-somastatin [35]. In this work there was improved precision

Diels–Alder reaction of β-fluoro-β-nitrostyrenes with cyclic dienes

• Savva A. Ponomarev,
• Roman V. Larkovich,
• Alexander S. Aldoshin,
• Andrey A. Tabolin,
• Sema L. Ioffe,
• Jonathan Groß,
• Till Opatz and
• Valentine G. Nenajdenko

Beilstein J. Org. Chem. 2021, 17, 283–292, doi:10.3762/bjoc.17.27

• stereochemical assignments were additionally confirmed by nuclear Overhauser effect spectroscopy (NOE). The peak of H6 was selected to be selectively excited for each isomer. As expected, in the case of endo-2l the NOE peaks resulted from the interaction of exo-H6 with H1 and H7a were observed. Whereas for exo

• -2l due to the opposite side position of endo-H6 there was no interaction observed. Thus, using these spectral data all the pairs of exo- and endo-isomers 2 obtained can be assigned unambiguously. Moreover, the 13C NMR spectra of the exo and endo-isomers exhibit a significant difference (approximately

Annulation of a 1,3-dithiole ring to a sterically hindered o-quinone core. Novel ditopic redox-active ligands

• Sergey V. Norkov,
• Anton V. Cherkasov,
• Andrey S. Shavyrin,
• Maxim V. Arsenyev,
• Viacheslav A. Kuropatov and
• Vladimir K. Cherkasov

Beilstein J. Org. Chem. 2021, 17, 273–282, doi:10.3762/bjoc.17.26

• stoichiometric mixture of 4 and monosodium salt of hfac, so that adduct 8 forms in a crystal phase only. Our studies indicate that the interaction of 4 with stable gem-dithiolates, such as sodium trithiocarbonate, malononitrile gem-dithiolate or 2,6-di-tert-butylphenol gem-dithiolate proceeds in a predictable

• amount of P(OMe)3 forms only the dioxaphospholane species, whereas the periphery carbonyl function remained unchanged [14]. o-Quinone 6a behaves in a similar manner: interaction with an excess amount of P(OMe)3 results in the formation of dioxaphospholane derivative 9 (Scheme 3, Figure S7 in Supporting

• molecular devices, since according to the EPR data for its monoreduced derivatives, there is a channel for the intraligand electron exchange interaction between the coordination sites of the molecule. Experimental All chemicals and solvents were purchased from commercial sources. Solvents were purified in

Exploring the possibility of using fluorine-involved non-conjugated electron-withdrawing groups for thermally activated delayed fluorescence emitters by TD-DFT calculation

• Dongyang Chen and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2021, 17, 210–223, doi:10.3762/bjoc.17.21

• geometries indicate that the carbazoles adopt a significantly twisted conformation (dihedral angles > 50o) in order to minimize their interaction with the acceptor group. Specifically, for 2CzCF3 the carbazoles are twisted to 60.2o and 70.5o with respect to the bridging phenyl ring while for 2CzSF5, due to

Au(III) complexes with tetradentate-cyclam-based ligands

• Ann Christin Reiersølmoen,
• Thomas N. Solvi and
• Anne Fiksdahl

Beilstein J. Org. Chem. 2021, 17, 186–192, doi:10.3762/bjoc.17.18

• showed no interaction with Au(III), as expected. A similar resistance to coordinate was observed for the open diamides 1c–e. The phosphorus containing ligand 1c did undergo phosphorus oxidation instead of Au(III) coordination. No effect was obtained by refluxing or by adding additives, such as silver

Multiswitchable photoacid–hydroxyflavylium–polyelectrolyte nano-assemblies

• Alexander Zika and
• Franziska Gröhn

Beilstein J. Org. Chem. 2021, 17, 166–185, doi:10.3762/bjoc.17.17

• particles, and information on the molecular structure was gained by UV–vis spectroscopy. Isothermal titration calorimetry (ITC) provided information on the thermodynamics and interaction forces in the supramolecular assembly formation. Keywords: electrostatic self-assembly; hydroxyflavylium

• molecular recognition processes have been established based on different non-covalent interactions such as hydrogen bonding [9][10][11][12], π–π interaction [13][14][15][16][17], hydrophobic effects, and amphiphilicity [18][19][20][21]. It has been highly desirable to establish concepts that could be

• polyelectrolyte which can be altered through irradiation, the Flavy molecule may associate with the polyelectrolyte via hydrogen bonding and dipolar interaction, which will also respond to the pH value, either by a direct pH change or via the effect of the photoexcitation of the photoacid. To state the assembly

Insight into functionalized-macrocycles-guided supramolecular photocatalysis

• Minzan Zuo,
• Krishnasamy Velmurugan,
• Kaiya Wang,
• Xueqi Tian and
• Xiao-Yu Hu

Beilstein J. Org. Chem. 2021, 17, 139–155, doi:10.3762/bjoc.17.15

• , this hybrid material rapidly degraded MO (≈98%) within 10 min, whereas freshly prepared TiO2 reached a value of ≈47%. This may be due to the synergic effect of β-CD and the AuNCs, which relies on two aspects: i) the host–guest interaction between β-CD and MO could lead to the Au cores being directly

Tuning the solid-state emission of liquid crystalline nitro-cyanostilbene by halogen bonding

• Subrata Nath,
• Alexander Kappelt,
• Matthias Spengler,
• Bibhisan Roy,
• Jens Voskuhl and
• Michael Giese

Beilstein J. Org. Chem. 2021, 17, 124–131, doi:10.3762/bjoc.17.13

• Subrata Nath Alexander Kappelt Matthias Spengler Bibhisan Roy Jens Voskuhl Michael Giese Organic Chemistry, University of Duisburg Essen, Universitätsstraße 7, 45141 Essen, Germany 10.3762/bjoc.17.13 Abstract The first example of halogen-bonded fluorescent liquid crystals based on the interaction

• behaviour of halogen-bonded liquid crystals has been reported. In 2014, Tothadi and Desiraju reported on a new supramolecular synthon based on the non-covalent interaction between 1,4-dinitrobenzene and iodobenzene [13]. Their structural analysis of a series of ternary cocrystals revealed that the nitro

• entities [14][15][16][17]. However, no examples for supramolecular materials employing this complementary interaction have been reported so far. In the present study we report the first halogen-bonded liquid crystal based on the complementary binding of nitro-cyanostilbene and tetrafluoroiodobenzene

Supramolecular polymers with reversed viscosity/temperature profile for application in motor oils

• Jan-Erik Ostwaldt,
• Christoph Hirschhäuser,
• Stefan K. Maier,
• Carsten Schmuck and
• Jochen Niemeyer

Beilstein J. Org. Chem. 2021, 17, 105–114, doi:10.3762/bjoc.17.11

• constants, based on a sixfold hydrogen-bonding interaction, strengthened by coulombic interactions (see Figure 2a) [20][21]. The GCP motif has successfully been applied for the formation of supramolecular polymers in earlier works [22][23][24][25]. The ionic nature of the GCP motif allows self-pairing even

Supramolecular polymerization of sulfated dendritic peptide amphiphiles into multivalent L-selectin binders

• David Straßburger,
• Svenja Herziger,
• Katharina Huth,
• Moritz Urschbach,
• Rainer Haag and
• Pol Besenius

Beilstein J. Org. Chem. 2021, 17, 97–104, doi:10.3762/bjoc.17.10

• -selectin binders; multivalency; self-assembly in water; supramolecular polymers; Introduction Deciphering the interaction of artificial molecular building blocks with biological components is a key element on the way to understanding and selectively manipulating biological systems. Throughout nature

Synthesis of aryl 2-bromo-2-chloro-1,1-difluoroethyl ethers through the base-mediated reaction between phenols and halothane

• Yukiko Karuo,
• Ayaka Kametani,
• Atsushi Tarui,
• Kazuyuki Sato,
• Kentaro Kawai and
• Masaaki Omote

Beilstein J. Org. Chem. 2021, 17, 89–96, doi:10.3762/bjoc.17.9

• carbon that was explained by an orbital interaction between the n orbital (fluorine) and the π orbital [44]. A literature survey revealed that Yagupol’skii et al. have achieved the first synthesis of aryl or alkyl 2-bromo-2-chloro-1,1-difluoroethyl ethers by the reaction of alcohols with halothane as

The fluorescence of a mercury probe based on osthol

• Guangyan Luo,
• Zhishu Zeng,
• Lin Zhang,
• Zhu Tao and
• Qianjun Zhang

Beilstein J. Org. Chem. 2021, 17, 22–27, doi:10.3762/bjoc.17.3

• fluorescence spectrum (λex = 325 nm) of the OST probe following interaction with Hg2+ at different concentrations. With the increase of the Hg2+ concentration, the fluorescence intensity at 406 nm showed an increase of the Hg2+ dependence. The fluorescence intensity reached the maximum when 1.0 equivalent of

• ), indicating that OST and Hg2+ formed a 2:2 complex. 1H NMR titration analysis of the mode of interaction between the probe and Hg2+ The chemical shift of the resonance peak between the OST probe and Hg2+ in a 1H NMR titration experiment was used to infer the binding mode of the probe and Hg2+. Figure 6 shows

• a 1H NMR titration of OST in the presence of Hg2+ at different concentrations. With the addition of Hg2+, the OST proton resonances shift. At n(Hg2+)/n(OST) = 1, the chemical shift of the proton signals did not change, indicating that the interaction ratio of OST and Hg2+ was 1:1. At this time, the

Synthesis, crystal structures and properties of carbazole-based [6]helicenes fused with an azine ring

• Daria I. Tonkoglazova,
• Anna V. Gulevskaya,
• Konstantin A. Chistyakov and
• Olga I. Askalepova

Beilstein J. Org. Chem. 2021, 17, 11–21, doi:10.3762/bjoc.17.2

• quinoxaline-fused hybrid 10a is intermediate (52.8° and 50.5°). Comparing the sum of the inner helix torsion angles of the helicenes 10a–c and 12 reveals the same patterns. Evidently, the repulsive interaction of the H(14) and H(g) atoms of 10c is the main reason for the observed extra twisting, whereas

• opinion. Apparently, interaction of this type is also realized in solution since the signal of the inner helix proton in the 1H NMR spectra of azine-fused [6]helicenes appeared in the low field at δ 9.3–9.7 ppm. A similar pattern was observed by us in the structures of the azine-fused [5]helicenes [72

• in its length from the standard single C(sp2)–C(sp2) bond (ca. 1.48 Å). The X-ray analysis of quinoxaline-fused [6]helicene 10a revealed the presence of the face-to-face π–π interaction between the helicene aggregates. The racemic aggregation was composed by (P)- and (M)-enantiomers on the manner of

Molecular basis for protein–protein interactions

• Brandon Charles Seychell and
• Tobias Beck

Beilstein J. Org. Chem. 2021, 17, 1–10, doi:10.3762/bjoc.17.1

• an electrostatic interaction between two molecules at 10 Å is around 1 kJ/mol, which is much higher than any other force at such a distance [47]. Long-range electrostatic interactions are affected by the net charges of the protein, i.e., proteins with a different net charge are electrostatically

• are electrostatically attracted to each other. On the other hand, the identical monomers in homooligomeric complexes have identical net charges, and thus, in theory, long-range electrostatic forces oppose their attraction. As a result, the actual interaction in close proximal proteins is not governed

• by the net charge but by different localised charges on the accessible surface residues in the protein monomers. This creates a delicate balance between the interface interaction and the desolvation energy, which affects the binding free energy. After binding occurs, ionisation changes can be induced

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

Beilstein J. Org. Chem. 2020, 16, 2971–2982, doi:10.3762/bjoc.16.247

• antibiotic, is used for the treatment of resistant bacterial infections. Its interaction with a small peptidic segment of the bacteria cell wall is a classic example of molecular recognition [6][7]. Peptides are often substrates for protease enzymes [8][9]. Enzymologists have studied the chemical principles

• behind the substrate recognition and catalytic reactivity for a long time. Hence, there is a wealth of knowledge on the type of interaction of small peptide sequences with specific partners. Researchers designed several artificial peptide-based receptors for molecular recognition purposes [10][11][12][13

• organic fluorophore (reporter) with a specific peptide sequence is the common approach for designing peptide-based fluorescent probes [16]. Fluorophores on peptidic arms perform as reporter during the interaction with biomolecules [17][18]. The interaction with biomolecules will alter the fluorescence

Naphthalonitriles featuring efficient emission in solution and in the solid state

• Sidharth Thulaseedharan Nair Sailaja,
• Iván Maisuls,
• Jutta Kösters,
• Alexander Hepp,
• Andreas Faust,
• Jens Voskuhl and
• Cristian A. Strassert

Beilstein J. Org. Chem. 2020, 16, 2960–2970, doi:10.3762/bjoc.16.246

• reported for these kind of compounds. At 77 K, non-radiative decays caused by the interaction with the solvent are suppressed and charge transfer states are destabilized. Therefore, the emission at low temperature is originated by singlet states with higher π–π* character, if compared with rt. Except for

• causing a slight SQ along with AIEE. The excited state of NMe2 shows a strong interaction with water molecules causing a prominent SQ effect and AIEE by decoupling from H2O. DLS studies were carried out to assure the aggregation at structural level. These measurements were done only when aggregates were

Construction of pillar[4]arene[1]quinone–1,10-dibromodecane pseudorotaxanes in solution and in the solid state

• Xinru Sheng,
• Errui Li and
• Feihe Huang

Beilstein J. Org. Chem. 2020, 16, 2954–2959, doi:10.3762/bjoc.16.245

• the hydrogen atoms on the ethoxy groups. It is worth mentioning that we did not find any interaction of the benzoquinone subunit of the host with the guest molecule. Host–guest complexation in solution In order to further study the host–guest binding properties of H and G, we explored the complexation

UV resonance Raman spectroscopy of the supramolecular ligand guanidiniocarbonyl indole (GCI) with 244 nm laser excitation

• Tim Holtum,
• Vikas Kumar,
• Daniel Sebena,
• Jens Voskuhl and
• Sebastian Schlücker

Beilstein J. Org. Chem. 2020, 16, 2911–2919, doi:10.3762/bjoc.16.240

• (CBS) [6][7][8][9]. The GCP takes part selectively and efficiently in the complexation of carboxylates based on the electrostatic interaction between the positively charged CBS and the negatively charged carboxylate in the combination with hydrogen bonding, enabling molecular recognition even in the

Dirhamnolipid ester – formation of reverse wormlike micelles in a binary (primerless) system

• David Liese,
• Hans Henning Wenk,
• Xin Lu,
• Jochen Kleinen and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2020, 16, 2820–2830, doi:10.3762/bjoc.16.232

• interaction of the alkyl chains. Keywords: dirhamnolipid ester; gemini surfactant; rheology; reverse wormlike micelle (RWLM); Introduction Surfactants have both hydrophilic and hydrophobic groups and are therefore amphiphilic molecules. Due to their unique molecular structure, surfactants are essential

Synthesis and investigation of quadruplex-DNA-binding, 9-O-substituted berberine derivatives

• Jonas Becher,
• Daria V. Berdnikova,
• Heiko Ihmels and
• Christopher Stremmel

Beilstein J. Org. Chem. 2020, 16, 2795–2806, doi:10.3762/bjoc.16.230

• -inflammatory [25], antibacterial [26][27], and anticancer reagents [28][29]. The latter property is mainly based on the binding interaction of berberine with nucleic acids and the resulting inhibition of topoisomerase and telomerase [2][30]. Most notably, berberine (1a) induces a strong growth inhibition in

• unit and was the strongest with a chain length of n = 5 (Figure 3). In the case of a2, the positive band of this G4-DNA at 265 nm showed only small fluctuations upon the interaction with the ligands, whereas the intensity of the broad red-shifted shoulder at 295 nm slightly increased at higher LDR. In

Synthesis of purines and adenines containing the hexafluoroisopropyl group

• Viacheslav Petrov,
• Rebecca J. Dooley,
• Alexander A. Marchione,
• Elizabeth L. Diaz,
• Brittany S. Clem and
• William Marshall

Beilstein J. Org. Chem. 2020, 16, 2739–2748, doi:10.3762/bjoc.16.224

• 3b was a sharp and well-resolved doublet (δ = −69.95 ppm, JFH = 6.9 Hz in CDCl3), the analogous resonance in the major isomer 3a was significantly broadened (δ = −68.95 ppm, ∆√1/2 = 60Hz, CDCl3), indicating a restricted rotation around the C–N bond, likely due to the steric interaction of the CF3

• , it was demonstrated that the majority of the reactions of 1 can involve monomeric hexafluorothioacetone (HFTA) as long as the reaction is carried out in a polar and nucleophilic solvent, such as DMF or DMSO [23]. One can speculate that an alternative mechanism may involve the interaction of monomeric

• mentioned above, the broadening of the resonances corresponding to the CF3 group as observed in the 19F NMR spectra of derivatives 3a, 4a, and 4b at ambient temperature is likely to be related to a restricted rotation around the C–N bond as a result of the steric interaction between the fluorine atoms of

Selective recognition of ATP by multivalent nano-assemblies of bisimidazolium amphiphiles through “turn-on” fluorescence response

• Rakesh Biswas,
• Surya Ghosh,
• Shubhra Kanti Bhaumik and
• Supratim Banerjee

Beilstein J. Org. Chem. 2020, 16, 2728–2738, doi:10.3762/bjoc.16.223

• ) values were significantly reduced and eventually became negative (Table 1) indicating a strong interaction of the negatively charged ATP with the aggregates. An appreciable increase in the size of the nanoaggregates was also observed upon addition of ATP (Table 1) pointing to the formation of larger co

Optical detection of di- and triphosphate anions with mixed monolayer-protected gold nanoparticles containing zinc(II)–dipicolylamine complexes

• Lena Reinke,
• Julia Bartl,
• Marcus Koch and
• Stefan Kubik

Beilstein J. Org. Chem. 2020, 16, 2687–2700, doi:10.3762/bjoc.16.219

• development of optical probes [1][2][3][4][5][6]. They are accessible in different sizes and shapes, can be stabilized by immobilizing suitable ligands, and can easily be functionalized with ligands containing binding sites that mediate the interaction with the analyte. Different strategies allow analyte

• binding of these anions to the immobilized receptor units strengthened their interaction with a simultaneously present bis(imidazolium) ion, which in turn caused nanoparticle crosslinking [16][17]. Our group recently showed that a mixed monolayer-protected AuNP containing solubilizing triethylene glycol

• receptors based on other scaffolds [22][23][24][25]. To test whether this binding motif induces AuNP crosslinking, we synthesized nanoparticles containing peripheral zinc(II)–DPA complexes together with a solubilizing triethylene glycol-based ligand in different ratios and studied their interaction with

Activation of pentafluoropropane isomers at a nanoscopic aluminum chlorofluoride: hydrodefluorination versus dehydrofluorination

• Maëva-Charlotte Kervarec,
• Thomas Braun,
• Mike Ahrens and
• Erhard Kemnitz

Beilstein J. Org. Chem. 2020, 16, 2623–2635, doi:10.3762/bjoc.16.213

• CF3CFDCH2C6D5 (12) (Scheme 2, bottom), with only 22% conversion. The low conversion in C6D6 could be a consequence of a possible interaction of the aromatic solvent with the surface of ACF, which would result in the blocking of the acidic sites, and thus hamper the adsorption of the substrates. Indeed, in a

• previous study, a pulse TA experiment suggested the presence of a strong interaction between benzene and the surface of ACF [38]. This result was further confirmed by 1H MAS NMR spectroscopy. Note, that 10a was activated under mild conditions without the use of an additional hydrogen source, which often

• for the transformation in the presence of silane, the conversions reached over 99% after 7 days at 70 °C, which underlines the significant role of the silane in the reaction mixture. The improved conversion can generally arise from an interaction of silane with the surface of ACF, also competing with

Anion exchange resins in phosphate form as versatile carriers for the reactions catalyzed by nucleoside phosphorylases

• Julia N. Artsemyeva,
• Ekaterina A. Remeeva,
• Tatiana N. Buravskaya,
• Irina D. Konstantinova,
• Roman S. Esipov,
• Anatoly I. Miroshnikov,
• Natalia M. Litvinko and
• Igor A. Mikhailopulo

Beilstein J. Org. Chem. 2020, 16, 2607–2622, doi:10.3762/bjoc.16.212

• employing nucleoside phosphorylases as biocatalysts. The enzymatic reaction of PF-1Pis and heterocyclic bases is a key step of the transglycosylation strategy for the synthesis of biologically important nucleosides. The reactions of phosphorolysis and interaction of the resulting PF-1Pis with heterocyclic

• -1Pis, and its interaction with 2-chloroadenine (2ClAde) catalyzed by E. coli PNP was studied. Work-up of the reaction mixture and purification as described above gave dRib-1Pi (Ba2+) in 93% yield. The reaction reached the equilibrium after incubation of the reaction mixture at 47 °C for 72 h with 88