Carbazole-functionalized hyper-cross-linked polymers for CO₂ uptake based on Friedel–Crafts polymerization on 9-phenylcarbazole

• Dandan Fang,
• Xiaodong Li,
• Meishuai Zou,
• Xiaoyan Guo and
• Aijuan Zhang

Beilstein J. Org. Chem. 2019, 15, 2856–2863, doi:10.3762/bjoc.15.279

• microporous HCPs and came to the conclusion that 2D and 3D-conjugated architectures with nonplanar rigid conformation and dendritic building blocks were favorable for getting a high BET specific surface area [6][19][20][21][23][24][25]. Qiao synthesized five microporous materials using carbazole with

One-pot synthesis of substituted pyrrolo[3,4-b]pyridine-4,5-diones based on the reaction of N-(1-(4-hydroxy-6-methyl-2-oxo-2H-pyran-3-yl)-2-oxo-2-arylethyl)acetamide with amines

• Valeriya G. Melekhina,
• Andrey N. Komogortsev,
• Boris V. Lichitsky,
• Vitaly S. Mityanov,
• Artem N. Fakhrutdinov,
• Arkady A. Dudinov,
• Vasily A. Migulin,
• Yulia V. Nelyubina,
• Elizaveta K. Melnikova and
• Michail M. Krayushkin

Beilstein J. Org. Chem. 2019, 15, 2840–2846, doi:10.3762/bjoc.15.277

• fragments proceeds first, followed by intramolecular cyclization (Scheme 4B). The structure of the 4-chloro-substituted pyrrolopyrimidinone 1e was proven by single crystal X-ray analysis (Figure 1). Despite the unambiguous dominance of the pyridone-based conformation in the solid state of 1e, two tautomers

Photoreversible stretching of a BAPTA chelator marshalling Ca²⁺-binding in aqueous media

• Aurélien Ducrot,
• Arnaud Tron,
• Robin Bofinger,
• Ingrid Sanz Beguer,
• Jean-Luc Pozzo and
• Nathan D. McClenaghan

Beilstein J. Org. Chem. 2019, 15, 2801–2811, doi:10.3762/bjoc.15.273

• calcium upon acting on the conformation of the adjacent binding site, rendering it a stronger or weaker binder. Photoswitching was studied in pseudo-physiological conditions (pH 7.2, [KCl] = 100 mM) and dissociation constants for azobenzene cis- and trans-isomers have been determined (0.230 μM and 0.102

A combinatorial approach to improving the performance of azoarene photoswitches

• Joaquin Calbo,
• Aditya R. Thawani,
• Rosina S. L. Gibson,
• Andrew J. P. White and
• Matthew J. Fuchter

Beilstein J. Org. Chem. 2019, 15, 2753–2764, doi:10.3762/bjoc.15.266

• consistent with our previous studies on 4pzH compared to 4pzMe [18], significantly larger half-lives are predicted for 4pzH-X derivatives compared to the dimethylated 4pzMe-X derivatives, which can be rationalized by the stabilizing short CH···π interactions in the T-shaped conformation of Z-4pzH-X (Figure 2

• substituted 4pzH-Pyr2, a perfect T-shape conformation is predicted as the minimum-energy structure (θ = 90°; Figure 3). The steric interaction between the second pyrrolidine group with the azo group (CH···azo-N distance of only 2.2 Å) prevents the favorable tilting observed for 4pzH-Pyr1. For the Z-4pzMe-X

• highly depends on the molecular conformation, significantly increasing for T-shaped structures (4pzH-X) compared to twisted arrangements (4pzMe-X), and thus leading to larger n–π* band separation for the 4pzH-X series [18]. On the other hand, the intense π–π* transition of the Z-isomer is generally found

Unexpected one-pot formation of the 1H-6a,8a-epiminotricyclopenta[a,c,e][8]annulene system from cyclopentanone, ammonia and dimethyl fumarate. Synthesis of highly strained polycyclic nitroxide and EPR study

• Sergey A. Dobrynin,
• Igor A. Kirilyuk,
• Yuri V. Gatilov,
• Andrey A. Kuzhelev,
• Olesya A. Krumkacheva,
• Matvey V. Fedin,
• Michael K. Bowman and
• Elena G. Bagryanskaya

Beilstein J. Org. Chem. 2019, 15, 2664–2670, doi:10.3762/bjoc.15.259

• molecules 1 and 6 is characterized by an elongation of the bonds C6A–C7 1.579(2), C8–C8A 1.573(2) Å in 1 and C3B–C6A 1.580(2), C8–C8A 1.573(2) Å in 6. The conformation of the azepane ring in 1 is close to a distorted boat with a kink at the C3A–N1 line, while in 6 the conformation of this ring is close to a

AgNTf₂-catalyzed formal [3 + 2] cycloaddition of ynamides with unprotected isoxazol-5-amines: efficient access to functionalized 5-amino-1H-pyrrole-3-carboxamide derivatives

• Ziping Cao,
• Jiekun Zhu,
• Li Liu,
• Yuanling Pang,
• Laijin Tian,
• Xuejun Sun and
• Xin Meng

Beilstein J. Org. Chem. 2019, 15, 2623–2630, doi:10.3762/bjoc.15.255

• , followed by the fragmentation process to give an unusual α-imino silver carbene species D. The intermediate D should be able to isomerize to D’ by conformation rotation to facilitate the addition of activated methene to Ag-carbene, thus forming a new silver species E with a 5-membered ring. The leaving of

1,5-Phosphonium betaines from N-triflylpropiolamides, triphenylphosphane, and active methylene compounds

• Vito A. Fiore,
• Chiara Freisler and
• Gerhard Maas

Beilstein J. Org. Chem. 2019, 15, 2603–2611, doi:10.3762/bjoc.15.253

• chemically equivalent atoms in the CXY fragment of some betaines (mainly those with X = Y = CN) also indicates that free rotation around the C3–C4 bond is slow on the NMR time scale around 295 K. A major difference between the E and Z-betaines 3 lies in the conformation at the C2–C3 single bond. The torsion

A toolbox of molecular photoswitches to modulate the CXCR3 chemokine receptor with light

• Xavier Gómez-Santacana,
• Sabrina M. de Munnik,
• Tamara A. M. Mocking,
• Niels J. Hauwert,
• Shanliang Sun,
• Prashanna Vijayachandran,
• Iwan J. P. de Esch,
• Henry F. Vischer,
• Maikel Wijtmans and
• Rob Leurs

Beilstein J. Org. Chem. 2019, 15, 2509–2523, doi:10.3762/bjoc.15.244

• parent azobenzene compound 2a allowing flexibility of the molecules except for the conformation of the trans and cis-azobenzene moieties, which were fixed in the lowest energy conformation to ensure a shape that has also been validated by crystallographic data [27]. The results show a reasonable overall

Self-assembled coordination thioether silver(I) macrocyclic complexes for homogeneous catalysis

• Zhen Cao,
• Aline Lacoudre,
• Cybille Rossy and
• Brigitte Bibal

Beilstein J. Org. Chem. 2019, 15, 2465–2472, doi:10.3762/bjoc.15.239

• analysis of monocrystals revealed the syn-conformation of 1 (Scheme 1). A variable temperature 1H NMR (VT-NMR, Figures S10–12 in Supporting Information File 1) experiment conducted on syn-1 in the range of –30 to 110 °C in C2D2Cl4 showed the broadening of proton signals, due to the restricted rotation of

Ultrafast processes triggered by one- and two-photon excitation of a photochromic and luminescent hydrazone

• Alessandro Iagatti,
• Baihao Shao,
• Alberto Credi,
• Barbara Ventura,
• Ivan Aprahamian and
• Mariangela Di Donato

Beilstein J. Org. Chem. 2019, 15, 2438–2446, doi:10.3762/bjoc.15.236

• observed on a 10 ps timescale, and the almost complete recovery of the transient signal occurs in 34 ps. The very short excited state lifetime observed in methanol agrees with the low fluorescence in this solvent. Possibly, in the protic solvent the molecule adopts a less planar conformation, because of

• transfer nature, so that it can be stabilized in polar media where its lifetime slightly increases. In the protic solvent, however, where the molecule can adopt a partially twisted conformation, the increased conformational disorder most probably activates different non-radiative decay channels, shortening

Photochromic diarylethene ligands featuring 2-(imidazol-2-yl)pyridine coordination site and their iron(II) complexes

• Andrey G. Lvov,
• Max Mörtel,
• Anton V. Yadykov,
• Frank W. Heinemann,
• Valerii Z. Shirinian and
• Marat M. Khusniyarov

Beilstein J. Org. Chem. 2019, 15, 2428–2437, doi:10.3762/bjoc.15.235

• good accordance with previous DFT calculations [37], the molecule shows exclusively antiparallel conformation [8] of the thiophene and imidazole groups of the photoactive diarylethene moiety, with the respective α-methyl groups pointing in different directions. The thiophene and imidazole rings are

• rotated out of the cyclohexenone plane by 47.7° and 44.1°, respectively. The distance between the reactive carbon atoms is 3.6 Å. This value is shorter than 4.2 Å, which is favorable for photocyclization [38]. The cyclohexenone moiety adopts a distorted half-chair (sofa) conformation, with the phenyl

• that bond. Two iron(II) centers are 8.057 Å apart in the dimer. The ligand 6 appears in the open-ring form and the parallel conformation [8], with the α-methyl groups pointing in similar directions. While still appearing in a distorted half-chair conformation, the phenyl substituent of the

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

• the oxazolone pseudo-peptide showed intramolecular C=O···HN(II) hydrogen bonding in a seven-membered ring leading to a γ-turn conformation. This fact was supported by a solution-state NMR and molecular modeling studies. The oxazolone pseudotetrapeptide was found to be a better Cl−-selective

• conformation [5]. Amongst these, the use of sugar-derived TAAs in peptidomimetics is less explored. The linear tri-/tetrapeptides and spiro-peptides at the anomeric position of mannofructose are known [6][7][8]. Stick and co-workers have reported the synthesis of tetrasubstituted sugar furanoid amino acid

• , we obtained an oxazolone ring containing pseudo peptides 1 and 2a, respectively (Figure 1) The NMR studies of pseudotetrapeptide 2a indicated a γ-turn conformation stabilized by the intramolecular hydrogen bonding [(II)NH···O=C] in a seven-membered ring. The oxazolone pseudotetrapeptide 2a

Reversible switching of arylazopyrazole within a metal–organic cage

• Anton I. Hanopolskyi,
• Soumen De,
• Michał J. Białek,
• Yael Diskin-Posner,
• Liat Avram,
• Moran Feller and
• Rafal Klajn

Beilstein J. Org. Chem. 2019, 15, 2398–2407, doi:10.3762/bjoc.15.232

• switching to the Z isomer was accompanied by the release of one of the two guests from the cage and the formation of a 1:1 cage/Z-arylazopyrazole inclusion complex. DFT calculations suggest that this process involves a dramatic change in the conformation of the cage. Back-isomerization was induced with

• moieties), but a significantly larger offset in the horizontal direction (the distance between para carbon atoms of the two guests, d = 11.154 Å vs 10.638 Å for the major isomer; see Figure S15, Supporting Information File 1). The difference between the major (93%) and the minor (7%) conformation of the

• -like shape (in contrast, the conformation of the bound guest is very similar to that of free Z-1). The optimized model of (Z-1)2 features strong interactions between the host and the guest. In particular, Z-1’s methyl groups Ha and Hc reside in close proximity to 2’s acidic imidazole protons (H1 and H4

Excited state dynamics for visible-light sensitization of a photochromic benzil-subsituted phenoxyl-imidazolyl radical complex

• Yoichi Kobayashi,
• Yukie Mamiya,
• Katsuya Mutoh,
• Hikaru Sotome,
• Masafumi Koga,
• Hiroshi Miyasaka and
• Jiro Abe

Beilstein J. Org. Chem. 2019, 15, 2369–2379, doi:10.3762/bjoc.15.229

• structure at 625 nm. The spectral shift with the increase in temperature is most probably due to the rigidity of the environment of molecules. At 77 K, it is expected that the solvent is too rigid for benzil to change the conformation in the excited state, namely, the conformation of benzil is fixed to the

• skewed conformation. On the other hand, it is expected that the increase in the temperature to 100 K softens the rigid matrix and allows the benzil to form the planar conformation at the T1 state. The energy level of the T1 state of benzil was estimated from the phosphorescence at 100 K because the T1

• state of benzil in solution forms the planar conformation. The energy level of the T1 state was determined by an edge of the high energy side of the phosphorescence, where a tangent line crosses the x-axis. The energy level of the T1 state of benzil is estimated to be 53 kcal mol−1, which is consistent

Current understanding and biotechnological application of the bacterial diterpene synthase CotB2

• Ronja Driller,
• Daniel Garbe,
• Norbert Mehlmer,
• Monika Fuchs,
• Keren Raz,
• Dan Thomas Major,
• Thomas Brück and
• Bernhard Loll

Beilstein J. Org. Chem. 2019, 15, 2355–2368, doi:10.3762/bjoc.15.228

• CotB2 from the open, inactive, to the closed, active conformation have been obtained in great detail, allowing us to draw detailed conclusions regarding the catalytic mechanism at the molecular level. Moreover, numerous alternative geranylgeranyl diphosphate cyclization products obtained by CotB2

• ) [12] to the acyclic terpene synthase substrate geranylgeranyl diphosphate 3 (GGDP) [1][13][14][15][16]. Following initial substrate binding and folding in a product-like conformation, the cyclization reaction can be subdivided into three steps: (1) generation of a reactive allyl carbocation as a

• labeling [34]. Another important step towards a deeper understanding of the cyclization mechanism was the availability of crystal structures (Table 1) revealing structural snapshots along the reaction trajectory commencing with the open, inactive conformation completing with the closed, active conformation

Mono- and bithiophene-substituted diarylethene photoswitches with emissive open or closed forms

• A. Lennart Schleper,
• Mariano L. Bossi,
• Vladimir N. Belov and
• Stefan W. Hell

Beilstein J. Org. Chem. 2019, 15, 2344–2354, doi:10.3762/bjoc.15.227

• and 470 nm. In this case, the difference in emission between asymmetric and symmetric substitution patterns was negligible. This feature can be explained by the fact that due to the twisted conformation of the open form, the emission transition involves the isolated benzothiophene unit (including the

Perspective isomorphs – a new classification of molecular structures based on artistic and chemical concepts

• Jannis Neumann,
• Ansgar Schnurr and
• Hermann A. Wegner

Beilstein J. Org. Chem. 2019, 15, 2319–2326, doi:10.3762/bjoc.15.224

• acrylic glass discs. The exemplary molecules (methane, fluoromethane and difluoromethane) were installed by hanging the individual atoms representing their conformation and the point of view to give the viewer the possibility to comprehend the congruency of the perspective isomorphs (Figure 6 and

• allow comparing different structures and their affinity to potential binding sites [20]. However, in all approaches, again, the ‘viewing point’ is neglected. The researcher is present as an all-seeing being. Furthermore, the molecules are usually optimized in their geometry and conformation to the

• lowest energy before comparison. Our concept of perspective isomorphs is in this context unique: First, it is not restricted to a specific conformation due to an external requirement. Second, the hypothetical view from a specific point is compared, not the overall shape, placing crucial importance on the

Harnessing enzyme plasticity for the synthesis of oxygenated sesquiterpenoids

• Melodi Demiray,
• David J. Miller and
• Rudolf K. Allemann

Beilstein J. Org. Chem. 2019, 15, 2184–2190, doi:10.3762/bjoc.15.215

• = 5.17, t, JH,H = 7.0 Hz) due to the presence of the methoxy group two carbon atoms away. The ADS-catalysed 1,11-cyclisation of diphosphate 11 suggests that the 8-methoxy group prevents the formation of a conformation conducive to isomerisation to NDP (4, Scheme 1) and hence 1,6-cyclisation to generate a

• as anchimeric assistance is hampered by unknowns such as the conformation of binding to the enzyme and what effect the extra bulk of the substituents has upon the results observed, but nevertheless such empirical results will accumulate to inform future investigations. This reversal of the

Azologization and repurposing of a hetero-stilbene-based kinase inhibitor: towards the design of photoswitchable sirtuin inhibitors

• Christoph W. Grathwol,
• Nathalie Wössner,
• Sören Swyter,
• Adam C. Smith,
• Enrico Tapavicza,
• Robert K. Hofstetter,
• Anja Bodtke,
• Manfred Jung and
• Andreas Link

Beilstein J. Org. Chem. 2019, 15, 2170–2183, doi:10.3762/bjoc.15.214

• photoswitchable, compounds 4a and 4b were synthesized to test the influence of a rigid conformation around the C=C double bond on sirtuin inhibition. Interestingly, this increased rigidity provokes a complete loss of activity against Sirt1. Despite the fact, that all mammalian sirtuins possess profound similarity

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

• the kinetic rate of the equilibrium between 18a and 18b, making both rotamers observable in the 1H NMR spectra. Conversely, after deprotonation of the ammonium moieties the macrocycle 18a is forced to adopt a helix-type contracted conformation (two slowly interconverting rotamers 18c and 18d) with a

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

• →29.2 ppm. Thus, these data clearly indicated that the calix[6]arene threaded by dibenzylammonium axles adopted a cone-conformation. A close inspection of the region between 4.8 and 5.2 ppm in the 1D and 2D NMR spectra, revealed the presence of the triple-threaded (7+)36 pseudo[4]rotaxane as a less

• at 3.44/4.32, 3.39/4.22, and 3.58/4.66 ppm which were 1J correlated with carbon resonances at 27.7, 27.9, and 29.1 ppm, respectively, attributable to ArCH2Ar groups of calix[6]-wheels between syn oriented aromatic rings. Consequently, the three calix[6]-wheels in (7+)36 adopt a cone conformation

• evidences for the formation of the (4+)36 pseudo[4]rotaxanes was obtained by a 1H NMR study (Figure 8d). A careful analysis of the ArCH2Ar region of these spectra evidenced again a syn orientation of the aromatic rings of calix[6]-wheels corresponding to a cone conformation, which was also confirmed by the

α-Photooxygenation of chiral aldehydes with singlet oxygen

• Dominika J. Walaszek,
• Magdalena Jawiczuk,
• Jakub Durka,
• Olga Drapała and
• Dorota Gryko

Beilstein J. Org. Chem. 2019, 15, 2076–2084, doi:10.3762/bjoc.15.205

• –C–C–O torsion angles of the diol unit [27][28][29]. The negative sign of CE at 310 nm in the recorded spectra for both analyzed compounds syn-6 and anti’-6 correlates to the negative O–C–C–O torsion angle. Based on the preferred gauche conformation of the diol unit with large substituents (O–C–C–O

• ). Stereoselective α-photooxygenation of 3,4-diphenylbutanal (1) with 1O2. Schematic representation of the in situ methodology and preferred conformation of diols with Mo2 core. Asymmetric synthesis of 3,4-diphenylbutane-1,2-diol. Stereoselectivity of α-photooxygenation reaction of 3,4-diphenylbutanal (1

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

• adopt the conformation in which three phthalimide units are cis,trans-orientated. Acting as electron-deficient macrocyclic hosts, the synthesized O6-corona[3]arene[3]tetrazines self-regulated conformational structures to complex anions in the gas phase and in the solid state owing to the anion–π

• tetrazine and phenolic oxygen and the high stability of corona[6]arene macrocycle under the reaction conditions. The spectroscopic data supported the macrocyclic structure of all products. To determine the structure beyond any doubt, and also to shed light on the conformation of phthalimide-containing O6

• -corona[6]arenes in the solid state, high quality single crystals of 3a were grown at room temperature from diffusion of diethyl ether vapor into the solution of 3a in acetonitrile. X-ray diffraction analysis revealed that the macrocycle 3a adopted an interesting conformation. As depicted in Figure 1, it

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

• intermediates, which reflect the initial conformation of the substrate, geranylfarnesyl diphosphate (GFPP). However, it remains unclear how the initial conformation of GFPP is controlled, and which part(s) of the GFPP molecule are important for its fixation inside the substrate-binding pocket. Here, we present

• ) triggering the biosynthetic cyclization cascade by the elimination of pyrophosphate or by protonation; (ii) preorganization of the substrate to generate the reactive conformation; (iii) protection of reactive intermediates from water; and (iv) termination of the reaction by deprotonation or hydration. We

• previously established the importance of conformation in the carbocation cyclization cascade [1], focusing on two sesterterpenes, i.e., quiannulatene [1][2] and sesterfisherol [3][4][5], as representative examples. These two sesterterpenes are synthesized via a 5/12/5 tricyclic intermediate, which leads to a

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

• towards hybrid (22AG, 46AG) and antiparallel (HRAS) G4-DNA, whereas the second group (dyes 1s, 1u, 1v, 17a and 18a) shows fluorimetric selectivity for parallel G4-DNA forms (c-kit2, c-kit87up, c-myc). To verify the preferences of the dyes with respect to the conformation of the G4 analytes, we analysed