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

• change of the pH value from pH 7.0 to pH 5.0 leads to an addition of one hydroxy group. This means that the number of possible hydrogen bonds increases from four at pH 7.0 to five at pH 5.0. Yet, the added hydroxy group is in a position where steric hindrance can play a major role. Furthermore, Flavy and

• the photoacid also form nano-assemblies on their own, which are also dependent on the pH value (see Supporting Information File 1). The assemblies are expected to form due to hydrogen bonds and ionic-dipole interaction. Already the raw data (Figure 8) clearly show an exothermic, an endothermic, and

• and one charge plus four hydrogen bonds, which corresponds to one Flavy for example. In difference, the second and fourth binding step are endothermic with ΔH2 = 64.5 kJ/mol and ΔH4 = 75.5 kJ/mol. Here, the association is entropically driven with ΔS2 = 0.22 kJ/mol/K and ΔS4 = 0.22 kJ/mol/K, indicating

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

• interactions [17][18]. By a careful design of the corresponding building blocks, extensive multilateral hydrogen bonds between the amino acid sequences of the oligopeptide backbone lead to secondary structures that direct the equilibrium to polymeric nano-scaled assemblies. A well-studied receptor making use

Circularly polarized luminescent systems fabricated by Tröger's base derivatives through two different strategies

• Cheng Qian,
• Yuan Chen,
• Qian Zhao,
• Ming Cheng,
• Chen Lin,
• Juli Jiang and
• Leyong Wang

Beilstein J. Org. Chem. 2021, 17, 52–57, doi:10.3762/bjoc.17.6

• rac-TBPP/DGG = 1:80, a mirror symmetry was observed in the CPL spectra of the co-gel at the molar ratio of rac-TBPP/LGG = 1:80 (Figure 2d). rac-TBPP contains pyridine units, and the gelator DGG has the carboxyl groups. Therefore, hydrogen bonds might be formed between pyridine in rac-TBPP and the

• could be involved in the formation of various hydrogen bonds (Figure 3b, Figure S7, Supporting Information File 1). At the molar ratio of rac-TBPP/DGG = 1:16, the intensity of the peak at 1691 cm−1 decreases, and the peak at 1729 cm−1 brodens. A new peak adjacent to 1645 cm−1 appears at 1627 cm−1. The

• results demonstrate that some of the acid–acid hydrogen bonds between DGG molecules might be replaced by acid–pyridine hydrogen bonds between DGG and rac-TBPP [27]. In addition, the possible influence of the stoichiometric ratios to the morphologies of rac-TBPP/DGG co-gels was investigated using a

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

• . In obligate complexes, the interface is characterised by hydrophobic and aromatic residues while in non-obligate, the residues are more polar and charged, with the interface area being smaller [55] and containing more hydrogen bonds [56]. PPIs can also be differentiated by either being transient

Chiral anion recognition using calix[4]arene-based ureido receptors in a 1,3-alternate conformation

• Tereza Horáčková,
• Jan Budka,
• Vaclav Eigner,
• Wen-Sheng Chung,
• Petra Cuřínová and
• Pavel Lhoták

Beilstein J. Org. Chem. 2020, 16, 2999–3007, doi:10.3762/bjoc.16.249

• . The shapes and geometries of anions are widely different, and therefore the design of corresponding tailor-made receptors is based mostly on more directional interactions, such as hydrogen bonds. Indeed, an incredible number of neutral receptors bearing amide, sulfonamide, urea, thiourea, pyrrole, or

• chain of calixarene molecules joined together by intermolecular hydrogen bonds between the ureido groups (the C=O···H–N distances were 2.293 and 2.048 Å). One of the ureido functions in the macrocycle also held acetone via a C=O···H–N hydrogen bond (2.085 Å) and via a C=O···H–C bond (2.670 Å) from the

• the dimeric motif. X-ray structure of 7d, showing hydrogen bonds between the ureido units (green) and hydrogen bonding of acetone molecules (black). One alkyl group in each calixarene was removed for better clarity. 1H NMR titration of 7c with N-acetyl-ᴅ-phenylalaninate and N-acetyl-ʟ-phenylalaninate

Selected peptide-based fluorescent probes for biological applications

• Debabrata Maity

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

• ). The inhibition by peptide 9 is found to be in a reversible and noncompetitive way. Molecular modeling shows four cationic ammonium groups forming ion pairs and hydrogen bonds with negatively charged residues, such as Glu217, Asp60B, Asp147 and Glu217, respectively and completely block the central pore

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

• together by C–H…N intermolecular hydrogen bonds with distances of 3.006 Å for C–H(2e)/N(6) and 3.083 Å for C–H(2d)/N(6) while involving hydrogen atoms of the tolyl moieties and the nitrogen atoms of nitrile groups. Then, these dimeric substructures are linked by C–H…N intermolecular interactions to

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

• in the solid state. From single crystal X-ray diffraction, the linear guest molecules thread into cyclic pillar[4]arene[1]quinone host molecules in the solid state, stabilized by CH∙∙∙π interactions and hydrogen bonds. The bromine atoms at the periphery of the guest molecule provide convenience for

• bonds. Specifically, there are four hydrogen atoms on the guest molecule to form multiple CH∙∙∙π interactions with the 1,4-diethoxybenzene subunits of the host. In addition, the two bromine atoms at the periphery of the guest molecule are outside the host cavities and form moderate hydrogen bonds with

• crystallography revealed that two host molecules complex one guest molecule, forming a [3]pseudorotaxane in the solid state (Figure 1). In the crystal structure, the alkyl chain of the guest is threaded through the cavities of two host molecules, which is stabilized by multiple CH∙∙∙π interactions and hydrogen

Controlled decomposition of SF₆ by electrochemical reduction

• Sébastien Bouvet,
• Bruce Pégot,
• Stéphane Sengmany,
• Erwan Le Gall,
• Eric Léonel,
• Anne-Marie Goncalves and
• Emmanuel Magnier

Beilstein J. Org. Chem. 2020, 16, 2948–2953, doi:10.3762/bjoc.16.244

• supporting electrolytes based on tetrabutylammonium (TBA) structures after anion exchange. This poor resolved signal is quite classical for such species due to hydrogen bonds. Another important point is the production of H+ ions at the counter electrode because of the oxidation of acetonitrile [31][32

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

• -covalent interactions namely hydrogen bonds, van der Waals, and/or hydrophobic interactions [1][2][3][4][5]. In this context, Schmuck and co-workers have introduced a class of synthetic receptors based on the guanidiniocarbonyl pyrrole (GCP) moiety (cf. Figure 1 top right) as a carboxylate binding site

Incorporation of a metal-mediated base pair into an ATP aptamer – using silver(I) ions to modulate aptamer function

• Marius H. Heddinga and
• Jens Müller

Beilstein J. Org. Chem. 2020, 16, 2870–2879, doi:10.3762/bjoc.16.236

• to release a DNA-bound cargo (in the form of small organic molecules) [10]. Similarly, metal ions can trigger DNA folding into a catalytically active topology [11][12]. Metal-mediated base pairs are artificial base pairs in which hydrogen bonds between the complementary nucleobases are formally

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

• electrostatic and (C–H)···O− hydrogen bonds involving the acidic proton at the 2-position of the imidazolium moiety to bind to ATP and other phosphate analytes [46]. A number of cyclophanes and tweezers [53][54][55][56] have been reported possessing the following common structural features: a) the presence of

Thermodynamic and electrochemical study of tailor-made crown ethers for redox-switchable (pseudo)rotaxanes

• Henrik Hupatz,
• Marius Gaedke,
• Hendrik V. Schröder,
• Julia Beerhues,
• Arto Valkonen,
• Fabian Klautzsch,
• Sebastian Müller,
• Felix Witte,
• Kari Rissanen,
• Biprajit Sarkar and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2020, 16, 2576–2588, doi:10.3762/bjoc.16.209

• -8 (DBC8, Figure 1), which bind through noncovalent interactions. In detail, these interactions are strong hydrogen bonds between ether oxygen atoms and ammonium protons. In addition, weaker C–H···O hydrogen bonds with the CH2 groups adjacent to the ammonium nitrogen as well as π–π-interactions

• the experiment. The folded structure observed in the crystal structure hints towards a possible “side-on” complex, where the ammonium axle is not threading through the ring of the macrocycle, yet still forms hydrogen bonds to the crown ether [24][25] (see spectroelectrochemical measurements below

• strength of the hydrogen bonds in the neutral complex and Coulomb repulsion in the oxidized complex [35]. This effect is less pronounced for the complex A2·PF6@exTTFC7 because the TTF unit is more distant to the ammonium unit [37]. The macrocycle bisTTFC8, bearing two TTF units, shows a broadening of the

Water-soluble host–guest complexes between fullerenes and a sugar-functionalized tribenzotriquinacene assembling to microspheres

• Si-Yuan Liu,
• Xin-Rui Wang,
• Man-Ping Li,
• Wen-Rong Xu and
• Dietmar Kuck

Beilstein J. Org. Chem. 2020, 16, 2551–2561, doi:10.3762/bjoc.16.207

• 1505.9611 (Δ = + 5.2 ppm). The surprising presence of six equivalents of water points to the formation of strong hydrogen bonds between the sugar ester bonds of TBTQ-(OAcG)6 and the water molecules as guests. However, the origin of this intriguing observation associated with the attachment of just two

Comparative ligand structural analytics illustrated on variably glycosylated MUC1 antigen–antibody binding

• Christopher B. Barnett,
• Tharindu Senapathi and
• Kevin J. Naidoo

Beilstein J. Org. Chem. 2020, 16, 2540–2550, doi:10.3762/bjoc.16.206

• analysis to consider how the sugar moiety could interact with the antibody (Tables S1–S7 in Supporting Information File 1). In solution, hydrogen bonds occur within the antigen between Arg5–Asp3 and Arg5–Pro8 (in order donor–acceptor) with occupancies of 31.83% and 14.32% (and 13.67%). For the Tn-antigen

• , the peptide portion has hydrogen bonds between Arg5–Pro8 (26.69% and 26.58%), Arg5–Asp3 (12.45%), an Arg5–Pro2 interaction is observed with an occupancy of 7.13%, and an intramolecular hydrogen bond between the C3 alcohol and the carbonyl of the N-acetyl moiety of the GalNAc has an occupancy of 6.92

• %. A shift in hydrogen-bonding populations on glycosylation and the appearance of the Arg5–Pro2 (7.13%) interaction aligns with the compact structure noted previously for the Tn-antigen. When bound, additional intramolecular hydrogen bonds are observed for the Tn-antigen with interactions between the

Styryl-based new organic chromophores bearing free amino and azomethine groups: synthesis, photophysical, NLO, and thermal properties

• Anka Utama Putra,
• Deniz Çakmaz,
• Nurgül Seferoğlu,
• Alberto Barsella and
• Zeynel Seferoğlu

Beilstein J. Org. Chem. 2020, 16, 2282–2296, doi:10.3762/bjoc.16.189

• planar to the dicyanomethylene group. A twist was observed between the dicyanomethylene and aminophenyl groups (salicylidenyl moiety for 8–12) with an angle of about 50°. In addition, the dyes 8–12 exhibited strong intramolecular O–H···N hydrogen bonds with lengths in the range of 2.63–2.64 Å (Figure 1

Naphthalene diimide bis-guanidinio-carbonyl-pyrrole as a pH-switchable threading DNA intercalator

• Poulami Jana,
• Filip Šupljika,
• Carsten Schmuck and
• Ivo Piantanida

Beilstein J. Org. Chem. 2020, 16, 2201–2211, doi:10.3762/bjoc.16.185

• energetically favourable non-covalent interactions, hydrogen bonds, and van der Waals interactions formed between the DNA/RNA and solvent, and between the compound 4 and solvent. The large positive entropy changes suggest solvent release upon binding, which makes a favourable contribution to the reaction Gibbs

Design, synthesis and application of carbazole macrocycles in anion sensors

• Alo Rüütel,
• Ville Yrjänä,
• Sandip A. Kadam,
• Indrek Saar,
• Mihkel Ilisson,
• Astrid Darnell,
• Kristjan Haav,
• Tõiv Haljasorg,
• Lauri Toom,
• Johan Bobacka and
• Ivo Leito

Beilstein J. Org. Chem. 2020, 16, 1901–1914, doi:10.3762/bjoc.16.157

• carboxylates were modelled computationally using COSMO-RS. Several observations were made from the computational structures. Intramolecular hydrogen bonds between the urea carbonyl and the carbazole NH protons were present in macrocycles MC001 and MC003, as indicated in Figure 4. The rings of these macrocycles

• studied anions. Additionally, for MC003, intramolecular hydrogen bonds could be present. For most anions, the champion molecules were MC007 and MC009. According to the computation results, neither benzoate nor pivalate were able to fit into the ring of these receptors because these anions were too large

Synthesis, docking study and biological evaluation of ᴅ-fructofuranosyl and ᴅ-tagatofuranosyl sulfones as potential inhibitors of the mycobacterial galactan synthesis targeting the galactofuranosyltransferase GlfT2

• Marek Baráth,
• Jana Jakubčinová,
• Zuzana Konyariková,
• Stanislav Kozmon,
• Katarína Mikušová and
• Maroš Bella

Beilstein J. Org. Chem. 2020, 16, 1853–1862, doi:10.3762/bjoc.16.152

• –GlfT2 interactions are depicted as dashed lines (yellow – hydrogen bonds, magenta – salt bridge, green – cation/π interaction). The Mg2+ ion is shown as a purple sphere. TLC analysis of the effects of the target compounds at 500 μM on the production of lower lipid-linked galactan precursors. CON

Models of necessity

• Timothy Clark and
• Martin G. Hicks

Beilstein J. Org. Chem. 2020, 16, 1649–1661, doi:10.3762/bjoc.16.137

• interaction between halogens and nucleophiles as repulsive; whereas we now know that halogen-bonding attractions can be as strong as hydrogen bonds. There will be more such examples but it is important to identify the encompassing phenomenon, rather than defining a wealth of apparently unique interactions

Rearrangement of o-(pivaloylaminomethyl)benzaldehydes: an experimental and computational study

• Csilla Hargitai,
• Györgyi Koványi-Lax,
• Tamás Nagy,
• Péter Ábrányi-Balogh,
• András Dancsó,
• Gábor Tóth,
• Judit Halász,
• Angéla Pandur,
• Gyula Simig and
• Balázs Volk

Beilstein J. Org. Chem. 2020, 16, 1636–1648, doi:10.3762/bjoc.16.136

• , indicating the presence of strong hydrogen bonds also in solution. These data suggest that the structures of the predominating conformers should be similar in the solid and liquid phases. Furthermore, we have managed to detect NOE steric proximities between the aldehyde H atom and the H-C(7) (in compounds 3b

Five-component, one-pot synthesis of an electroactive rotaxane comprising a bisferrocene macrocycle

• Natalie Lagesse,
• Luca Pisciottani,
• Maxime Douarre,
• Pascale Godard,
• Brice Kauffmann,
• Vicente Martí-Centelles and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2020, 16, 1564–1571, doi:10.3762/bjoc.16.128

• ). The isolated material had low solubility, which is likely due to self-aggregation via complementary amide hydrogen bonds. This prompted us to use a thread with bulky stopper groups to prepare the corresponding rotaxane compounds, which would increase the solubility by the formation of intramolecular

• macrocycle-thread hydrogen bonds, thereby reducing self-aggregation. To this end, a five-component clipping strategy was adopted using different tetrabutylsuccinamide threads (Figure 2) with varying hydrogen-bond basicity (amides > esters) [4][15]. Threads containing an ester group were selected as esters

• macrocycle–thread hydrogen bonds, with the other two macrocycle amides forming hydrogen bonds with the competitive crystallization solvent DMF. In contrast, rotaxane 1a presented four thread–macrocycle hydrogen bonds (Figure 7 and Table 1). The strength of the hydrogen bonds could be estimated by the donor

Synthesis, antiinflammatory activity, and molecular docking studies of bisphosphonic esters as potential MMP-8 and MMP-9 inhibitors

• Abimelek Cortes-Pacheco,
• María Adelina Jiménez-Arellanes,
• Francisco José Palacios-Can,
• José Antonio Valcarcel-Gamiño,
• Rodrigo Said Razo-Hernández,
• María del Carmen Juárez-Vázquez,
• Adolfo López-Torres and
• Oscar Abelardo Ramírez-Marroquín

Beilstein J. Org. Chem. 2020, 16, 1277–1287, doi:10.3762/bjoc.16.108

• kcal/mol; the observed energy values are shown in Table 7. Compound 3 displayed two hydrogen bonds. The first one was formed between a hydrogen atom of His162 with an oxygen atom from the ester moiety (the oxygen atom bound to the ethyl group of the phosphonate unit), with a calculated distance (O–H

• distance and an energy of −2.5 kcal/mol (Figure 4c). Compound 6 showed four hydrogen bonds that varied in force. Two were observed between an oxygen atom from an OEt moiety of a phosphonate group to amide hydrogen atoms localized between Ile159, Leu160, and Ala161 (Figure 4d). These interactions had energy

• values of −1.94 and −2.5 kcal/mol, which is regarded as characteristic for strong hydrogen bonds. The measured O–N distances had values of 3.15 and 2.67 Å. Another hydrogen-bond interaction was seen from an OEt moiety (from the phosphonate group coordinating the zinc ion), with a weak energy of −0.95

The charge-assisted hydrogen-bonded organic framework (CAHOF) self-assembled from the conjugated acid of tetrakis(4-aminophenyl)methane and 2,6-naphthalenedisulfonate as a new class of recyclable Brønsted acid catalysts

• Svetlana A. Kuznetsova,
• Alexander S. Gak,
• Yulia V. Nelyubina,
• Vladimir A. Larionov,
• Han Li,
• Michael North,
• Vladimir P. Zhereb,
• Alexander F. Smol'yakov,
• Artem O. Dmitrienko,
• Michael G. Medvedev,
• Igor S. Gerasimov,
• Ashot S. Saghyan and
• Yuri N. Belokon

Beilstein J. Org. Chem. 2020, 16, 1124–1134, doi:10.3762/bjoc.16.99

• , elemental analysis, and 1H NMR spectroscopy. The framework was supported by hydrogen bonds between the sulfonate anions and the ammonium cations of NDS and protonated TAPM moieties, respectively. The CAHOF material functioned as a new type of catalytically active Brønsted acid in a series of reactions

• developed [25][26][27][28][29][30][31][32][33][34][35][36]. Usually, a HOF is built from multitopic tectons that interact with their neighbors by directional hydrogen bonds, disfavoring close packing, and thus generating significant pore volumes within the crystal [25][26][27][28]. These heterogeneous

• parameters a = 20.6034(8) Å, b = 20.1330(8) Å, c = 22.4357(8) Å, β = 91.989(1)°, and cell volume = 9300.9(6) Å3 at 120 K. An asymmetric part of the unit cell contained two ammonium cations, four sulfonate anions, and nine water molecules, held together by numerous hydrogen bonds (Table S2, Supporting

Efficient synthesis of piperazinyl amides of 18β-glycyrrhetinic acid

• Dong Cai,
• ZhiHua Zhang,
• Yufan Meng,
• KaiLi Zhu,
• LiYi Chen,
• ChangXiang Yu,
• ChangWei Yu,
• ZiYi Fu,
• DianShen Yang and
• YiXia Gong

Beilstein J. Org. Chem. 2020, 16, 798–808, doi:10.3762/bjoc.16.73

• agent [12]. Piperazinyl amide fragments have the ability to form several hydrogen bonds, modulate the acid–base equilibrium constant and change the octanol–water partition coefficient [13]. They are considered as the basic motif for designing many biologically active molecules [14][15]. Some piperazinyl