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

• -derived tris(crown ether) host (eTC) via a dynamic covalent chemistry approach involving triple threading and a Grubbs-catalyzed ring-closing metathesis [68]. 1H NMR titration experiments have been used for the identification of co-conformations of the four related stable states of 19. The authors have

• mechanism has been proposed for the MIM macrocycle 19 involving a stepwise co-conformational progression. After the deprotonation of dibenzylammonium (DBA) sites, the rings prefer to move toward the adjacent N-methyl-1,2,3-triazolium (MTA) sites to the thermodynamically stable co-conformations rather than

Synthesis of 1-azaspiro[4.4]nonan-1-oxyls via intramolecular 1,3-dipolar cycloaddition

• Yulia V. Khoroshunova,
• Denis A. Morozov,
• Andrey I. Taratayko,
• Polina D. Gladkikh,
• Yuri I. Glazachev and
• Igor A. Kirilyuk

Beilstein J. Org. Chem. 2019, 15, 2036–2042, doi:10.3762/bjoc.15.200

• conformations of neighbouring geminal ethyl groups, thereby preventing averaging. In agreement with this conclusion, there are no large splittings in the EPR spectrum of 12c, and the line width is a bit greater than that in the spectra of similar nonspirocyclic 3,4-unsubstituted 2,2-diethylpyrrolidine

Synthesis and anion binding properties of phthalimide-containing corona[6]arenes

• Meng-Di Gu,
• Yao Lu and
• Mei-Xiang Wang

Beilstein J. Org. Chem. 2019, 15, 1976–1983, doi:10.3762/bjoc.15.193

• editing or varying the meta-substitution of arylenes within heteracalixaromatics into the para-substitution. In contrast to heteracalixaromatics which adopt generally 1,3-alternate conformations giving V-shaped cleft structures [17][18][19][20][21], the resulting coronarenes form, however, cylindroid

Inherent atomic mobility changes in carbocation intermediates during the sesterterpene cyclization cascade

• Hajime Sato,
• Takaaki Mitsuhashi,
• Mami Yamazaki,
• Ikuro Abe and
• Masanobu Uchiyama

Beilstein J. Org. Chem. 2019, 15, 1890–1897, doi:10.3762/bjoc.15.184

• 351-0198, Japan Graduate School of Pharmaceutical Sciences, University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 10.3762/bjoc.15.184 Abstract We previously showed that the regio- and stereoselectivity in terpene-forming reactions are determined by the conformations of the carbocation

• . Based on this analysis, it appears that the destination of the cyclization cascade is determined by the conformations of the carbocation intermediates, but not by enzymatic constraints. This insight is consistent with our previous findings [1]. Conclusion In order to clarify the influence of the

Identification of optimal fluorescent probes for G-quadruplex nucleic acids through systematic exploration of mono- and distyryl dye libraries

• Xiao Xie,
• Michela Zuffo,
• Marie-Paule Teulade-Fichou and
• Anton Granzhan

Beilstein J. Org. Chem. 2019, 15, 1872–1889, doi:10.3762/bjoc.15.183

• mirroring their conformations. Specifically, parallel G4s cluster in the upper left part of the plot (red dots), as a result of high fluorescence response with 18a and moderate-to-low response with 1p. Hybrid G4s (green dots) produce moderate light-up values for 18a and high ones for 1p, thus clustering on

• the existence of an equilibrium between a monomolecular antiparallel form and a bimolecular parallel one, affected by K+ and oligonucleotide concentration [86]. As already suggested, this oligonucleotide is probably present as a mixture of conformations in our working conditions [14]. It is thus

The cyclopropylcarbinyl route to γ-silyl carbocations

• Xavier Creary

Beilstein J. Org. Chem. 2019, 15, 1769–1780, doi:10.3762/bjoc.15.170

• of cation 37. This study at the B3LYP/6-31G* level suggested that migration of bond a in 43 is not viable since the resultant cation 47 is not an energy minimum at this level, but a transition state. However, a current study at the M062X/6-311+G** level finds that both conformations 47a and 47b are

Synthesis and conformational preferences of short analogues of antifreeze glycopeptides (AFGP)

• Małgorzata Urbańczyk,
• Michał Jewgiński,
• Joanna Krzciuk-Gula,
• Jerzy Góra,
• Rafał Latajka and
• Norbert Sewald

Beilstein J. Org. Chem. 2019, 15, 1581–1591, doi:10.3762/bjoc.15.162

• calculated with the usage of the XPLOR-NIH program [34]. The obtained conformations were clustered based on the main chain backbone dihedral angles (φ and ψ) using the AmberTools package [35]. The first analysis of the number of obtained distance constrains clearly suggested that peptides containing ʟ-amino

An azobenzene container showing a definite folding – synthesis and structural investigation

• Abdulselam Adam,
• Saber Mehrparvar and
• Gebhard Haberhauer

Beilstein J. Org. Chem. 2019, 15, 1534–1544, doi:10.3762/bjoc.15.156

• possible conformations [cis,trans-(M), cis,trans-(P), cis,cis-(M,M), cis,cis-(M,P) and cis,cis-(P,P)]. However, it turned out that the P conformers represent no minima on the potential energy surface. Furthermore, single point calculations by means of the density functionals B3LYP and B3LYP-D3 were

Diazocine-functionalized TATA platforms

• Roland Löw,
• Talina Rusch,
• Fynn Röhricht,
• Olaf Magnussen and
• Rainer Herges

Beilstein J. Org. Chem. 2019, 15, 1485–1490, doi:10.3762/bjoc.15.150

• to measure kinetics on surfaces [15]. The C–O stretching frequencies proved to be ideal reporter signals to determine the configuration and to measure kinetics in monolayers of azo-TATAs on surfaces. Results and Discussion To obtain information on preferred conformations of 1 and 2 in their cis and

• for both compounds as the thermodynamically most stable isomers. For the corresponding trans-configuration two different conformations were found: the twist and the chair structures. The twist conformation is about 2.5 kcal mol−1 more stable than the chair conformation. Our calculations predict

Synthesis and biological evaluation of truncated derivatives of abyssomicin C as antibacterial agents

• Leticia Monjas,
• Peter Fodran,
• Johanna Kollback,
• Carlo Cassani,
• Thomas Olsson,
• Maja Genheden,
• D. G. Joakim Larsson and
• Carl-Johan Wallentin

Beilstein J. Org. Chem. 2019, 15, 1468–1474, doi:10.3762/bjoc.15.147

• conformations and with expected interaction points in the binding site, providing suitable docking scores (see Supporting Information File 1). The key interactions include a hydrogen bond to the backbone of Arg-45 and lipophilic interactions in the deep pocket defined by Phe-241 and Leu-34 (Figure 2). Our

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

• interesting new binding properties. During the last six years, our group have developed a series of naphthol-based macrocyclic receptors [24][25][26][27][28][29]. Of them, oxatub[4]arene [30][31] and zorb[4]arene [32][33] show multiple conformations due to the flipping of naphthalenes and thus resulted in a

• rather wide guest scope. Therefore, we wondered whether multiple conformations would be observed by incorporating the 2,3-dialkoxynaphthalene units into tetralactam macrocycles as the sidewalls. How would this affect their binding affinity and selectivity of the resulting macrocycles? Herein, we describe

• pre-organized. In addition, there exist two conformations for both macrocycles 1 and 2 because the two 2,3-dibutoxynaphthalene moieties can be aligned either in parallel or antiparallel orientation (Scheme 1). These two conformations have different cavities defined by the parallel or antiparallel

Anomeric sugar boronic acid analogues as potential agents for boron neutron capture therapy

• Daniela Imperio,
• Erika Del Grosso,
• Silvia Fallarini,
• Grazia Lombardi and
• Luigi Panza

Beilstein J. Org. Chem. 2019, 15, 1355–1359, doi:10.3762/bjoc.15.135

• broadening of the H-2, H-3 and H-4 signals suggest a slow equilibrium between different conformations. After deprotection of the benzylidene group in addition to line broadening, signal superposition is observed, hampering any conclusion on the conformation of compound 11. In order to get more information

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

• by a hydrophobic mid-region, and adopts different conformations depending on different factors: the solvent, the nature of the guest molecule, the functionalization of the lower (OH) rim [16]. The 3D cavities and the π-electron-rich sulfonate groups endow them with fascinating affinities and

N-doped carbon dots covalently functionalized with pillar[5]arenes for Fe³⁺ sensing

• Jia Gao,
• Ming-Xue Wu,
• Dihua Dai,
• Zhi Cai,
• Yue Wang,
• Wenhui Fang,
• Yan Wang and
• Ying-Wei Yang

Beilstein J. Org. Chem. 2019, 15, 1262–1267, doi:10.3762/bjoc.15.123

• macrocyclic compounds, especially new macrocyclic arenes, have become one of the research hotspots in supramolecular chemistry [11][12][13][14]. Among them pillarenes as a relatively new family of pillar-shaped members discovered a decade ago have played a key role due to their unique conformations

Steroid diversification by multicomponent reactions

• Leslie Reguera,
• Cecilia I. Attorresi,
• Javier A. Ramírez and
• Daniel G. Rivera

Beilstein J. Org. Chem. 2019, 15, 1236–1256, doi:10.3762/bjoc.15.121

• the natural cationic peptide antibiotics [60] or as a way to constrain peptide sequences in protein epitope conformations [61]. In this regard, the groups of Rivera and Wessjohann have pioneered the utilization of MCRs for the conjugation of oligosaccharides [62] and peptides [63][64] to steroids

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

• macrocyclic structure in a stable conformation with all NH residues directed into the cavity. One way is to use 2,6-pyridine dicarboxamides as the bridging units which permits intramolecular hydrogen bonding within the cavity (Figure 1) [30]. This internal hydrogen bonding stabilizes conformations that have

• conformations is an outward directed NH residue. Solution-state NMR data suggests that the surrounding tetralactam in these [2]rotaxanes undergoes rapid exchange between these different conformations, a dynamic process that has been called macrcocyle breathing, and that there is also simultaneous co

• crystal structures of acene and azaacene guests inside tetralactam B with the surrounding macrocycle in chair or boat conformations [25]. Recent work has shown that water-soluble versions of anthracene tetralactam B can be threaded by water soluble squaraine dyes with very high affinities (Ka ≈ 109 M−1

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

• C-galactoside aglycons, we performed a 200 ns molecular dynamic simulation of 1b in the complex with galectin-1 and galectin-3. Starting conformations were selected with the galactopyranose of 1b positioned overlapping with the positions of the lactose or N-acetyllactosamine galactopyranoses in

Halogen bonding and host–guest chemistry between N-alkylammonium resorcinarene halides, diiodoperfluorobutane and neutral guests

• Fangfang Pan,
• Mohadeseh Dashti,
• Michael R. Reynolds,
• Kari Rissanen,
• John F. Trant and
• Ngong Kodiah Beyeh

Beilstein J. Org. Chem. 2019, 15, 947–954, doi:10.3762/bjoc.15.91

• incredibly effective tool for observing privileged conformations and structures [15][16][17][18][19]. From the crystallographic information we can extract the polymorphism, high Z’-value, twining, and disorder that provide insight into the dynamics of prenucleation assembly, nucleation, and crystal growth

• , and the resulting empty space, induces disorder for both the hexyl groups on the upper-rim of the cavitand, and the DIOFB molecules. Two preferred conformations of these systems were identified with a ratio of ca. 3:1 (Figure 3, Figures S1 and S3 in Supporting Information File 1). Due to the center of

• inversion, the two conformations show different dimerization modes (Supporting Information File 1, Figure S3). In 1&DIOFB_A, the two hex-NARBrs are linked by two DIOFB molecules via four Br···I halogen bonds with average RXB of 0.86. The two participating bromide anions are on adjacent “arms”; the remaining

Coordination chemistry and photoswitching of dinuclear macrocyclic cadmium-, nickel-, and zinc complexes containing azobenzene carboxylato co-ligands

• Jennifer Klose,
• Tobias Severin,
• Peter Hahn,
• Alexander Jeremies,
• Jens Bergmann,
• Daniel Fuhrmann,
• Jan Griebel,
• Bernd Abel and
• Berthold Kersting

Beilstein J. Org. Chem. 2019, 15, 840–851, doi:10.3762/bjoc.15.81

• drastically alter its structural properties and reactivities. Prominent examples are the cis-bromination of α,β-unsaturated carboxylato ligands [2], regioselective Diels–Alder reactions of encapsulated dienoate ligands [3], and the stabilization of unusual co-ligand conformations, respectively [4]. The

Strong hyperconjugative interactions limit solvent and substituent influence on conformational equilibrium: the case of cis-2-halocyclohexylamines

• Camila B. Francisco,
• Cleverton S. Fernandes,
• Ulisses Z. de Melo,
• Roberto Rittner,
• Gisele F. Gauze and
• Ernani A. Basso

Beilstein J. Org. Chem. 2019, 15, 818–829, doi:10.3762/bjoc.15.79

• most stable rotamer in each conformation (see Supporting Information File 2 for full numerical data). In the PCA (Figure 6), two principal components described 94% of the results. The PC1 is able to differentiate the variables according to the halogens, while the PC2 distinguish the two conformations

• ae. Then, considering all the interactions existent in both conformations, the ones involving the LPX are important for both conformers. However, what differs them are the interactions with the highest weight for ea. It is worth mentioning that the variables corresponding to the N–H bonds and LPN has

• RStudio, version 1.0.153 [45]. Conformations of cis-2-halocyclohexylamines, where X = F, Cl, Br and I. Variable-temperature 1H NMR spectra (500.13 MHz) for cis-2-chlorocyclohexylamine in dichloromethane-d2. Potential energy surfaces (PESs) for cis-2-halocyclohexylamines for the C2–C1–N–H dihedral angle

A diastereoselective approach to axially chiral biaryls via electrochemically enabled cyclization cascade

• Hong Yan,
• Zhong-Yi Mao,
• Zhong-Wei Hou,
• Jinshuai Song and
• Hai-Chao Xu

Beilstein J. Org. Chem. 2019, 15, 795–800, doi:10.3762/bjoc.15.76

• –Hammett scenario (Scheme 4) [42]. Specifically, the equilibrium of the conformations IV and IV′ is much faster than their respectively cyclizations to give V and V′. Since TS2 is relatively lower in energy than TS3, V is formed as the major product. Conclusion In summary, we have developed a

Stereochemical investigations on the biosynthesis of achiral (Z)-γ-bisabolene in Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 789–794, doi:10.3762/bjoc.15.75

• enantiomers by BbS, different NPP conformations inside the chiral environment of the active site in BbS have to be assumed (Figure 4B + 4C). The architecture of the active site may stay the same in both cases, so a fixed OPP moiety with binding by the trinuclear Mg2+ cluster and a comparable folding of the

Homo- and hetero-difunctionalized β-cyclodextrins: Short direct synthesis in gram scale and analysis of regiochemistry

• Gábor Benkovics,
• Mihály Bálint,
• Éva Fenyvesi,
• Erzsébet Varga,
• Szabolcs Béni,
• Konstantina Yannakopoulou and
• Milo Malanga

Beilstein J. Org. Chem. 2019, 15, 710–720, doi:10.3762/bjoc.15.66

• staggered conformations about the C5–C6 bond are generally of gt type, except for one case, the gg-oriented H6,6’A-tosyl group in 6A,6D-ditosyl-β-CD. This implies that the group is rotated completely outside its cavity, whereas in all other ditosyl derivatives positioning of the tosyl group partially over

Influence of per-O-sulfation upon the conformational behaviour of common furanosides

• Alexey G. Gerbst,
• Vadim B. Krylov,
• Dmitry A. Argunov,
• Maksim I. Petruk,
• Arsenii S. Solovev,
• Andrey S. Dmitrenok and
• Nikolay E. Nifantiev

Beilstein J. Org. Chem. 2019, 15, 685–694, doi:10.3762/bjoc.15.63

• of sulfates. Keywords: ab initio calculations; conformational analysis; furanosides; NMR; sulfation; Introduction Changes in the conformations of monosaccharides expectedly accompany their modification with different functional groups. Thus, spatial repulsion of silyl groups results in inversion or

• constants significantly differ for non-sulfated and per-O-sulfated furanosides which allows for a conclusion that their conformations are changed after the sulfation. To rationalize these changes, we undertook theoretical conformational analysis of monosaccharides 1–3 and 1s–3s. Conformational analysis of

• -energy conformers which differed from each other by less than 2 kcal/mol. The other conformations found had considerably higher energies. For non-sulfated structures 1–3 sometimes high-energy conformations were obtained with the same puckering state of the furanoside ring (see Tables in Supporting

Conformational signature of Ishikawa´s reagent using NMR information from diastereotopic fluorines

• Laize A. F. Andrade,
• Lucas A. Zeoly,
• Rodrigo A. Cormanich and
• Matheus P. Freitas

Beilstein J. Org. Chem. 2019, 15, 506–512, doi:10.3762/bjoc.15.44

• with the dihedral angle between coupled nuclei [7]. According to this relationship, the SSCC between antiperiplanar nuclei is larger than that observed between gauche nuclei. One-bond SSCCs (1J) can also provide relevant information on the conformations of a molecule. For example, the Perlin effect

• would then be worth to evaluate. It is worth mentioning, however, that the relative and interchangeable orientation of the atoms in a molecule (conformations) is dependent on the medium; while only intramolecular interactions drive the conformational stability of a molecule in the vacuum, the solvent

• polarity plays a significant role in the condensed phase. Thus, it is appropriate to study the conformations of Ishikawa´s reagent in different media, of low and high polarity. This is a challenging task, since the conformational analysis of flexible acyclic organic compounds using NMR SSCCs is more