Halides as versatile anions in asymmetric anion-binding organocatalysis

• Lukas Schifferer,
• Martin Stinglhamer,
• Kirandeep Kaur and
• Olga García Macheño

Beilstein J. Org. Chem. 2021, 17, 2270–2286, doi:10.3762/bjoc.17.145

• only a spectator linking the substrate and catalyst in the presence of an external nucleophile, halides can also be tuned to participate as the nucleophile in certain reactions. In theory, the close association of the catalyst and the anionic nucleophile might allow for better stereocontrol. An early

Constrained thermoresponsive polymers – new insights into fundamentals and applications

• Patricia Flemming,
• Alexander S. Münch,
• Andreas Fery and
• Petra Uhlmann

Beilstein J. Org. Chem. 2021, 17, 2123–2163, doi:10.3762/bjoc.17.138

Electron-rich triarylphosphines as nucleophilic catalysts for oxa-Michael reactions

• Susanne M. Fischer,
• Simon Renner,
• A. Daniel Boese and
• Christian Slugovc

Beilstein J. Org. Chem. 2021, 17, 1689–1697, doi:10.3762/bjoc.17.117

• acquiring the 31P NMR spectra, Petra Hofstadler for pre-studies and Karin Ratzenböck for discussion. Funding Funding by the Christian Doppler Research Association (Austrian Federal Ministry for Digital and Economic Affairs and the National Foundation for Research, Technology and Development) is gratefully

Chemical approaches to discover the full potential of peptide nucleic acids in biomedical applications

• Nikita Brodyagin,
• Martins Katkevics,
• Venubabu Kotikam,
• Christopher A. Ryan and
• Eriks Rozners

Beilstein J. Org. Chem. 2021, 17, 1641–1688, doi:10.3762/bjoc.17.116

• ., magnesium ions), and achieve remarkably complex folded structures. Nevertheless, the electrostatic repulsion is the main force that disfavors folding and association of nucleic acids. With this consideration in mind, neutral PNA was expected to have superior binding to negatively charged nucleic acids due

Icilio Guareschi and his amazing “1897 reaction”

• Gian Cesare Tron,
• Alberto Minassi,
• Giovanni Sorba,
• Mara Fausone and
• Giovanni Appendino

Beilstein J. Org. Chem. 2021, 17, 1335–1351, doi:10.3762/bjoc.17.93

A new glance at the chemosphere of macroalgal–bacterial interactions: In situ profiling of metabolites in symbiosis by mass spectrometry

• Marine Vallet,
• Filip Kaftan,
• Veit Grabe,
• Fatemeh Ghaderiardakani,
• Simona Fenizia,
• Aleš Svatoš,
• Georg Pohnert and
• Thomas Wichard

Beilstein J. Org. Chem. 2021, 17, 1313–1322, doi:10.3762/bjoc.17.91

• similarity with standards. Using combined imaging mass spectrometry and confocal laser scanning microscopy, we then linked the chemical and microscopic observations that characterise the symbiotic association (cLSM). Results and Discussion Comparative metabolomics using AP-SMALDI-HRMS identifies metabolites

Synthesis of 10-O-aryl-substituted berberine derivatives by Chan–Evans–Lam coupling and investigation of their DNA-binding properties

• Peter Jonas Wickhorst,
• Mathilda Blachnik,
• Denisa Lagumdzija and
• Heiko Ihmels

Beilstein J. Org. Chem. 2021, 17, 991–1000, doi:10.3762/bjoc.17.81

• , specifically 13- and 9-substituted berberine derivatives have gained much interest as selective DNA ligands that specifically target quadruplex DNA (G4-DNA) [23][24][25][26][27][28][29], i.e., non-canonical, biologically relevant DNA structures that are formed by the association of four guanine-rich DNA

• Information File 1). Only the absorption of compound 5a increased upon association with ct DNA. In general, a significant red shift of the absorption bands was observed during all titrations, which was more pronounced in the presence of 22AG (∆λ = 18–24 nm) than in the presence of ct DNA (∆λ = 8–12 nm

• ). Therefore, it is proposed that the association with the DNA causes a similar effect. Hence, the slightly increased emission intensity of the ligands 5a–d upon addition of DNA supposedly originates from the restricted conformational freedom of the ligand within the DNA binding pocket, which suppresses the

Synthetic reactions driven by electron-donor–acceptor (EDA) complexes

• Zhonglie Yang,
• Yutong Liu,
• Kun Cao,
• Xiaobin Zhang,
• Hezhong Jiang and
• Jiahong Li

Beilstein J. Org. Chem. 2021, 17, 771–799, doi:10.3762/bjoc.17.67

• depends on the association of eosin Y and oxidant 4 to a donor–acceptor EY–4 ground-system complex (high reactivity). Due to the ability of aryl groups to stabilize the formed alkenyl radical, this protocol could control regioselectivity efficiently with unsymmetrical alkynes. In addition, EPR

DNA with zwitterionic and negatively charged phosphate modifications: Formation of DNA triplexes, duplexes and cell uptake studies

• Yongdong Su,
• Maitsetseg Bayarjargal,
• Tracy K. Hale and
• Vyacheslav V. Filichev

Beilstein J. Org. Chem. 2021, 17, 749–761, doi:10.3762/bjoc.17.65

• ammonium group, providing a zwitterionic phosphate mimic. The resistance to enzymatic degradation, a higher thermal stability, and a faster association that was independent of ionic strength was observed for this N+-modified G-quadruplex (TG4T)4. These properties encouraged us to evaluate the N

Synthesis and physicochemical evaluation of fluorinated lipopeptide precursors of ligands for microbubble targeting

• Masayori Hagimori,
• Estefanía E. Mendoza-Ortega and
• Marie Pierre Krafft

Beilstein J. Org. Chem. 2021, 17, 511–518, doi:10.3762/bjoc.17.45

• peptide ligands dramatically increased cellular association in HER2-positive cells. Other lipids grafted to the RGD peptide and SG spacer were integrated in PEGylated liposomes and were efficiently associated with integrin αvβ3-expressing Colon-26 cells [25]. One of our general objectives is to synthesize

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

• thermodynamic equilibrium binding constants (K) and kinetic rates of association (kon) and dissociation (koff) in protein–ligand binding events [37]. In order to achieve this, they analysed the binding of four different proline-rich peptides to a 5-FTrp-labelled Src homology 3 (SH3) recognition protein domain

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

• pH-responsive nano-assemblies with switchable size and structure are formed by the association of a photoacid, anthocyanidin, and a linear polyelectrolyte in aqueous solution. Specifically, anionic disulfonated naphthol derivatives, neutral hydroxyflavylium, and cationic poly(allylamine) are used as

• addition of a fifth hydroxy group, more binding sites become available for the association with the poly(allylamine), leading to an increase in assembly size: More multivalent small molecules bind to the polyelectrolyte, interconnecting more polyelectrolyte molecules into larger aggregates. At the same

• . Thermodynamic analysis of the assembly process For understanding the differences of the assemblies, isothermal titration calorimetry (ITC) was performed to elucidate the thermodynamics and to gain insight into the building block interactions in the assembly process. Basically, ITC measures the association heat

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

• complexes (1:1, 2:1, 1:2, and 2:2). For the 1:1, 2:1, and 1:2 host–guest complexes, the thermodynamic association (Ka) and dissociation constants (Kd) for the reactive guests and photoproducts are crucial for the fundamental understanding of supramolecular noncovalent interactions [12][13]. In addition

• molecules can absorb light and transfer energy, making the assemblies an efficient light-harvesting system. The host–guest binding stoichiometry is 1:1, and the association constant (Ka) of WP5β-CAR was calculated to be (2.34 ± 2.06) × 105 M−1. This system can function as a photocatalyst for the reduction

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

• VII system requires a BU with strong dimerization tendency and a LU with precoordinating properties. For our purpose, we initially employed the guanidiniocarbonyl pyrrole (GCP) motif as a binding unit [19]. The GCP unit is a self-complementary zwitterion, which forms dimers with high association

• seen as a neutral analogue of the GCP motif. Due to the missing ionic interactions, the self-association is weaker, but still sufficiently strong, in aprotic solvents such as chloroform (Ka > 106 M−1) [27]. As for the LU, we chose the 1,1’-binaphthyl-2,2’-diamine (BINAM) backbone. The attachment of the

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

• modelled by the McGhee–von Hippel model of nonspecific protein binding to a surface [86]. In this model, the association with nucleic acids, quantified by KNA, is dependent on the cooperativity coefficient ω, which is based on the protein–protein association constant. A ω value of 1 represents no

• that a nucleic acid scaffold aids the assembly by concentrating assembly units and providing additional association energy. Some viral capsids can self-assemble around other scaffolds that mimic the viral genome in charge and size [89] or can also assemble without any scaffold to form empty capsid

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

• dissolves all anionic species tested, (ii) prevents the receptor molecule from self-association, and (iii) reduces the complexation constants to values easily measurable by 1H NMR titrations. A solution of an anion was gradually added to a solution of 7 or 8 in DMSO-d6 to obtain various calixarene/anion

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

• spectrometry results, we believed that the differences between the stoichiometric ratio of the complexation in the solid state and in solution could be owing to the competitive role of solvent molecules in the combination of H and G. The association constant (Ka) calculated by the nonlinear curve fitting

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

• disappearance of SF6 after 6 hours as well as all the fluorinated organic compounds. The only peak detected by 19F NMR is around −153 ppm. This value corresponds to the classical chemical shift range of a fluoride anion. Due to its broad appearance, we can postulate the association with cations coming from the

Using multiple self-sorting for switching functions in discrete multicomponent systems

• Amit Ghosh and
• Michael Schmittel

Beilstein J. Org. Chem. 2020, 16, 2831–2853, doi:10.3762/bjoc.16.233

• transformation: SelfSORT-I → SelfSORT-II → SelfSORT-III → SelfSORT-I (Figure 16) [64]. In this unprecedented three-step reaction cycle that was designed on the corresponding association constants, the supramolecular two-component equilateral triangle 54 was selected as the starting entity in the state SelfSORT-I

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

• berberine derivatives was synthesized by the Cu-catalyzed click reaction of 9-propargyladenine with 9-O-(azidoalkyl)berberine derivatives. The association of the resulting berberine–adenine conjugates with representative quadruplex-forming oligonucleotides 22AG dA(G3TTA)3G3 and a2 d(ACAG4TGTG4)2 was

• not provide evidence for a significant effect of the adenine unit on the binding affinity of the ligands, for example, by additional association with the loops, presumably because the adenine residue is sterically shielded by the neighboring triazole unit. Keywords: berberine alkaloids; DNA ligands

• delicate balance between the hydrophobic effects of the alkyl chain and the thermodynamically favorable interactions on the association of ammonium or pyridinium groups in the grooves and loops was assessed. In another approach with a cyanine-based ligand, the alkyl substituents with a suitable length were

Nocarimidazoles C and D, antimicrobial alkanoylimidazoles from a coral-derived actinomycete Kocuria sp.: application of ¹J_C,H coupling constants for the unequivocal determination of substituted imidazoles and stereochemical diversity of anteisoalkyl chains in microbial metabolites

• Md. Rokon Ul Karim,
• Enjuro Harunari,
• Amit Raj Sharma,
• Naoya Oku,
• Kazuaki Akasaka,
• Daisuke Urabe,
• Mada Triandala Sibero and
• Yasuhiro Igarashi

Beilstein J. Org. Chem. 2020, 16, 2719–2727, doi:10.3762/bjoc.16.222

• found in association with marine organisms such as invertebrates and plants [4][5]. Marine actinomycetes show unique physiological adaptations distinct from their terrestrial counterparts in terms of pressure, salinity, or low-temperature tolerance, which might affect their metabolic ability in their

• producing organisms to the marine ecosystem. Similarly to nocarimidazole B (4) and bulbimidazole A (5), 1 possesses the anteiso-branched alkanoyl chain. The absolute configurations of the anteiso-branched metabolites are in general expected to be S in an association to bacterial anteiso fatty acids, which

Particle size effect in the mechanically assisted synthesis of β-cyclodextrin mesitylene sulfonate

• Stéphane Menuel,
• Sébastien Saitzek,
• Eric Monflier and
• Frédéric Hapiot

Beilstein J. Org. Chem. 2020, 16, 2598–2606, doi:10.3762/bjoc.16.211

• reactants throughout the solid mixture under ball-milling conditions. A weak association of bulky substrates and/or their corresponding products with the CD cavities under ball-milling conditions improved the mobility of the partners in the solid state. The reaction reactivity and selectivity were then

Synthesis of 4-substituted azopyridine-functionalized Ni(II)-porphyrins as molecular spin switches

• Jannis Ludwig,
• Tobias Moje,
• Fynn Röhricht and
• Rainer Herges

Beilstein J. Org. Chem. 2020, 16, 2589–2597, doi:10.3762/bjoc.16.210

• diamagnetic (or the paramagnetic) species in the two photostationary states. The intermolecular association constants of pyridines as axial ligands to Ni-porphyrins as a function of their para substituents usually follow the Hammett relationship [5][12]. Hence, the association constants should also be

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

• -fullerene in co-organic solvents and aqueous solution was investigated by fluorescence spectroscopy and ultraviolet-visible spectroscopy. The association stoichiometry of the complexes TBTQ-(OG)6 with C60 and TBTQ-(OG)6 with C70 was found to be 1:1 with binding constants of Ka = (1.50 ± 0.10) × 105 M−1 and

• : fullerenes; host–guest systems; microspheres; supramolecular chemistry; tribenzotriquinacene; Introduction In the field of supramolecular chemistry, host–guest association through noncovalent interactions is an interesting and exciting topic, especially for the encapsulation of various fullerenes, such as

• a 1:1 stoichiometric ratio of both TBTQ-(OG)6 C60 and TBTQ-(OG)6 C70, and the association constants were calculated to be Ka = (1.50 ± 0.10) × 105 M−1 and Ka = (2.20 ± 0.16) × 105 M−1, respectively, using a global nonlinear curve fitting method (Figure 2) [49]. The slightly stronger association

Recent developments in enantioselective photocatalysis

• Callum Prentice,
• James Morrisson,
• Andrew D. Smith and
• Eli Zysman-Colman

Beilstein J. Org. Chem. 2020, 16, 2363–2441, doi:10.3762/bjoc.16.197

• intermediate 196. In 195 there is additional steric repulsion between the large R group and the thioxanthone that is not present in 195’, which results in a smaller association constant and a larger calculated separation between the allene and the chromophore in 195 (r = 510 pm) relative to 195’ (r = 363 pm

• ). As the efficiency of Dexter energy transfer decreases exponentially with distance, the larger gap results in lower sensitisation rates for 190. This, in combination with the difference in association constants, leads to greater racemisation of ent-194 and, therefore, a deracemisation with excellent