Mechanochemical synthesis of hyper-crosslinked polymers: influences on their pore structure and adsorption behaviour for organic vapors

• Sven Grätz,
• Sebastian Zink,
• Hanna Kraffczyk,
• Marcus Rose and
• Lars Borchardt

Beilstein J. Org. Chem. 2019, 15, 1154–1161, doi:10.3762/bjoc.15.112

• a decrease of the C–Cl vibration after the reaction. B: Low pressure nitrogen isotherm of NG-HCP demonstrating the textural properties. A: Evolution of pressure in the course of the reaction measured by the GTM system. The addition of 1 mL of Et2O is sufficient to drastically reduce the released

Precious metal-free molecular machines for solar thermal energy storage

• Meglena I. Kandinska,
• Snejana M. Kitova,
• Vladimira S. Videva,
• Stanimir S. Stoyanov,
• Stanislava B. Yordanova,
• Stanislav B. Baluschev,
• Silvia E. Angelova and
• Aleksey A. Vasilev

Beilstein J. Org. Chem. 2019, 15, 1096–1106, doi:10.3762/bjoc.15.106

• constants of metal complexes were determined and are in good agreement with the literature data for reference dyes. The temporal evolution of trans-to-cis isomerization was observed in a real-time regime. The dyes demonstrated a low intrinsic fluorescence of their Ba2+ complexes and high yield of E/Z

• characteristic changes in the absorption spectra of dye 4b–Ba2+ complex under optical excitation with λ = 488 nm and intensity of 14 mW cm−2. The temporal evolution of the absorption at specific wavelength of λabs = 500 nm is demonstrated in Figure 3b: during the first time interval from t1 = 10 s up to t2 = 180

• × 10−4 M) with Ba2+ (cM = 1 M) on the irradiation time. b) Temporal absorption evolution, measured at λabs = 500 nm, upon irradiation. Experimental conditions: Excitation wavelength λexc = 488 nm; excitation intensity 14 mW cm−2, solvent, ACN; pulse duration t = 180 s. UV–vis absorption spectra of dye

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

• yellow to colorless during the addition of the borane dimethyl sulfide complex. Upon complete consumption of 2, distilled water (15 mL) was added to the reaction mixture slowly (dropwise at first) while vigorous gas evolution was observed. After completion of the gas evolution, sodium hydroxide (14 mL

• for 2 h. The reaction mixture went from light yellow to colorless during the addition of the borane dimethyl sulfide complex. Upon complete consumption of the starting material, distilled water (0.66 mL) was added to the reaction mixture slowly (dropwise at first) while vigorous gas evolution was

• observed. After completion of the gas evolution, sodium hydroxide (131 µL, 0.131 mmol, 1 M) and hydrogen peroxide (33%, 13 µL, 0.131 mmol) were added, and the reaction mixture left for 2 h. Upon completion of the reaction, 1 M hydrochloric acid was added to the reaction mixture until the pH was

Mechanistic investigations on multiproduct β-himachalene synthase from Cryptosporangium arvum

• Jan Rinkel and
• Jeroen S. Dickschat

Beilstein J. Org. Chem. 2019, 15, 1008–1019, doi:10.3762/bjoc.15.99

• compound mixture need to be precise [1]. However, in some cases, compound mixtures have proven to be superior to the properties of the single compounds by evolution. Examples demonstrating this principle can be found in pheromone chemistry, like the bark beetle aggregation blend of ipsdienol, ipsenol and

• a single enzyme that can produce a beneficial mixture, the advantage for the producing organism is even higher. Therefore, selectivity is not in every case the highest goal for evolution. An enzyme class, which is highly prone to a regulation of product selectivity for the production of either one

Azologization of serotonin 5-HT₃ receptor antagonists

• Karin Rustler,
• Galyna Maleeva,
• Piotr Bregestovski and
• Burkhard König

Beilstein J. Org. Chem. 2019, 15, 780–788, doi:10.3762/bjoc.15.74

• thermal half-lives (THL) of the cis-isomers of compounds 5a, 5b, 12a, 16a–d, 23, and 28 was accomplished by monitoring the increase in absorbance which corresponds to the evolution of the trans-isomer after irradiation and exposure to dark. In contrast to the heterocyclic compounds 5a, 5b, 12a, and 16a–d

Synthesis of polydicyclopentadiene using the Cp₂TiCl₂/Et₂AlCl catalytic system and thin-layer oxidation of the polymer in air

• Zhargolma B. Bazarova,
• Ludmila S. Soroka,
• Alex A. Lyapkov,
• Мekhman S. Yusubov and
• Francis Verpoort

Beilstein J. Org. Chem. 2019, 15, 733–745, doi:10.3762/bjoc.15.69

• by a spectrophotometer Thermo Scientific Evolution 201 using a wavelength range from 200 to 900 nm. Infrared spectra of the polymer were registered applying an FTIR spectrometer Simeks FT-801 in the range from 500 to 4000 cm−1. A silicon plate with a diameter of 8 mm was applied to support the

Design, synthesis and spectroscopic properties of crown ether-capped dibenzotetraaza[14]annulenes

• Krzysztof M. Zwoliński and
• Julita Eilmes

Beilstein J. Org. Chem. 2019, 15, 617–622, doi:10.3762/bjoc.15.57

• cm−1; HR-ESIMS (+νe mode) m/z (%): [M + H]+ calcd for C48H55N6O7, 827.4132; found, 827.4135 (100), Δm = 0.3 ppm; anal. calcd for C48H54N6O7.CH2Cl2: C, 64.54; H, 6.19; N, 9.22; found: C, 64.81; H, 6.32; N, 8.85. Timeline for the structure evolution of crown-capped DBTAAs (created on the basis of

Back to the future: Why we need enzymology to build a synthetic metabolism of the future

• Tobias J. Erb

Beilstein J. Org. Chem. 2019, 15, 551–557, doi:10.3762/bjoc.15.49

• produced should not be dictated by the serendipity and constraints of evolution, but be accessible through rational design. However, this requires a fundamental understanding of those principles that are necessary for designing, realizing and operating multi-reaction sequences and metabolic networks de

• can these new enzyme reactions be identified or established? One option is the de novo-design of enzymes assisted by computational methods, which have been developed over the last couple of years. When combined with experimental evolution and elaborate screening methods, these efforts have allowed to

• methods that succeeded in creating active sites of remarkable promiscuous activities in the scaffold of existing enzymes [42]. Such computationally-created “catalytically diverse active sites” could be further developed towards a new activity through directed evolution. Without any question, screening

Synthesis and selected transformations of 2-unsubstituted 1-(adamantyloxy)imidazole 3-oxides: straightforward access to non-symmetric 1,3-dialkoxyimidazolium salts

• Grzegorz Mlostoń,
• Małgorzata Celeda,
• Katarzyna Urbaniak,
• Marcin Jasiński,
• Vladyslav Bakhonsky,
• Peter R. Schreiner and
• Heinz Heimgartner

Beilstein J. Org. Chem. 2019, 15, 497–505, doi:10.3762/bjoc.15.43

• evolution of carbon dioxide ceased. The mixture was stirred overnight, filtered and the filtrate was evaporated to dryness. The crude product was triturated again with diethyl ether and after few minutes filtered off. In some instances, products obtained thereby were dried over freshly prepared molecular

Aqueous olefin metathesis: recent developments and applications

• Valerio Sabatino and
• Thomas R. Ward

Beilstein J. Org. Chem. 2019, 15, 445–468, doi:10.3762/bjoc.15.39

• adamantyl group of catalyst 12. A simple filtration of the crude mixture through a cotton plug after RCM of substrate 54 yields the purified product with 53 ppm of residual ruthenium (Scheme 12). Metathesis with artificial metalloenzymes Directed evolution allows an iterative improvement by successive

• , yielding 85% of product 22 (Table 5). A substitution of lysine with histidine at position 198 (Table 5, entries 8 and 9) did not improve the catalytic efficiency of ArM 2 at pH 7.0. Jeschek et al. subsequently evolved ArM 1 in vivo by directed evolution of an artificial metathase [68]. Tethering an OmpA

• artificial metathase ArM 1. Upon addition of the umbelliferone precursor 62, RCM reaction occurs in AcONa/AcOH buffer (pH 4.0) in the presence of 0.5 M MgCl2. The formed umbelliferone (63) can be detected by fluorescence (Figure 3). The fifth generation Sav-mutant resulting from directed evolution (Sav_mut5

Olefin metathesis in multiblock copolymer synthesis

• Maria L. Gringolts,
• Yulia I. Denisova,
• Eugene Sh. Finkelshtein and
• Yaroslav V. Kudryavtsev

Beilstein J. Org. Chem. 2019, 15, 218–235, doi:10.3762/bjoc.15.21

• the parent homopolymers are exhausted. 1H NMR spectroscopy was implemented to track the evolution of the chain structure in the course of MCM between polybutadiene (PBD) or polyisoprene (PI) and olefin-containing polyesters or polyurethane, as well as changes in the chain stereospecificity during the

• transformations and ex situ NMR monitoring of the dyad composition evolution [90]. It was found that Gr1 first interacts with PCOE so that all Ru-carbenes become bound to those macromolecules approximately within one hour (Scheme 9, reaction 1 and Figure 7). Recall that the addition of Gr1 to a mixture of NB and

Computational characterization of enzyme-bound thiamin diphosphate reveals a surprisingly stable tricyclic state: implications for catalysis

• Ferran Planas,
• Michael J. McLeish and
• Fahmi Himo

Beilstein J. Org. Chem. 2019, 15, 145–159, doi:10.3762/bjoc.15.15

• substrates or, possibly more importantly, the evolution of ThDP-dependent enzymes to accept a wide range of non-native substrates, might not be as simple as may have been expected. Experimental All calculations were performed with the B3LYP-D3(BJ) [62][63][64][65] density functional method and using the

Ruthenium-based olefin metathesis catalysts with monodentate unsymmetrical NHC ligands

• Veronica Paradiso,
• Chiara Costabile and
• Fabia Grisi

Beilstein J. Org. Chem. 2018, 14, 3122–3149, doi:10.3762/bjoc.14.292

• a backbone-substituted N-alkyl, N'-aryl NHC ligand was reported by Collins et al. in 2007 (164, Figure 30) [52]. This complex represented an evolution of the chiral C2-symmetric system previously proposed by Grubbs (165, Figure 30) [53], in which the replacement of the phenyl groups on the backbone

Nucleofugal behavior of a β-shielded α-cyanovinyl carbanion

• Rudolf Knorr and
• Barbara Schmidt

Beilstein J. Org. Chem. 2018, 14, 3018–3024, doi:10.3762/bjoc.14.281

• that 13 had transferred its proton to the emerging, thermally stable [4] cleavage product 2K faster than to the residual PhCH2K (perhaps a problem of slow mixing). On the other hand, deprotonation of 13 by the Grignard reagent MeMgBr in THF was complete (quantitative CH4 evolution) within 20 min at 0

Olefin metathesis catalysts embedded in β-barrel proteins: creating artificial metalloproteins for olefin metathesis

• Daniel F. Sauer,
• Johannes Schiffels,
• Takashi Hayashi,
• Ulrich Schwaneberg and
• Jun Okuda

Beilstein J. Org. Chem. 2018, 14, 2861–2871, doi:10.3762/bjoc.14.265

• three-fold increase in ruthenium content as compared to cells lacking the Sav variant (80,000 Ru atoms per cell and 29,000 Ru atoms per cell, respectively) [47]. This system was subjected to directed evolution. The twenty amino acid positions closest to the active site were saturated, and the best

• mutant formed the starting variant for the next iterative round. As screening substrate, the pre-fluorescent styrene derivative 3 was used. Following RCM, the fluorescent molecule umbelliferone (4) was generated. In total, five rounds of directed evolution were performed, yielding the mutant

• [52][53], and hydrogen evolution [54]. Further, Lewis et al. employed the NB scaffold for epoxidation of styrene and other olefins [55]. In all studies, the catalyst incorporated into the NB scaffold showed increased activity as compared to the protein-free catalyst under similar conditions

Oxidative and reductive cyclization in stiff dithienylethenes

• Michael Kleinwächter,
• Ellen Teichmann,
• Lutz Grubert,
• Martin Herder and
• Stefan Hecht

Beilstein J. Org. Chem. 2018, 14, 2812–2821, doi:10.3762/bjoc.14.259

• radical cations [34][35] and simple dithienylethenes [36][37][38]. As such, we postulate an equilibrium between both E- and Z-radical cations with the latter rapidly reacting to the closed isomer. To gain a deeper mechanistic understanding of the oxidative cyclization, the evolution of the UV–vis

Non-native autoinducer analogs capable of modulating the SdiA quorum sensing receptor in Salmonella enterica serovar Typhimurium

• Matthew J. Styles and
• Helen E. Blackwell

Beilstein J. Org. Chem. 2018, 14, 2651–2664, doi:10.3762/bjoc.14.243

• and antagonism. Keywords: N-acyl L-homoserine lactone; LuxR-type receptor; Quorum sensing; Salmonella enterica serovar Typhimurium; SdiA; Introduction In the fight against bacterial infections, microbes have a decisive advantage over the medical community: evolution [1]. Using bacteriocidal or

Calixazulenes: azulene-based calixarene analogues – an overview and recent supramolecular complexation studies

• Paris E. Georghiou,
• Shofiur Rahman,
• Abdullah Alodhayb,
• Hidetaka Nishimura,
• Jaehyun Lee,
• Atsushi Wakamiya and
• Lawrence T. Scott

Beilstein J. Org. Chem. 2018, 14, 2488–2494, doi:10.3762/bjoc.14.225

• just a few. Reinhoudt has recently presented an overview of the historical evolution of the chemistry of the calixarenes [1]. Supramolecular applications, in particular, of many of the great number of creative derivatives of calixarenes which have been and continue to be synthesized are widely being

Synthesis of a leopolic acid-inspired tetramic acid with antimicrobial activity against multidrug-resistant bacteria

• Luce Mattio,
• Loana Musso,
• Leonardo Scaglioni,
• Andrea Pinto,
• Piera Anna Martino and
• Sabrina Dallavalle

Beilstein J. Org. Chem. 2018, 14, 2482–2487, doi:10.3762/bjoc.14.224

• , is an imperative goal to stay ahead of the evolution of antibiotic resistance. Herein we report the synthesis of a 3-decyltetramic acid analogue of the ureido dipeptide natural antibiotic leopolic acid A. The key step in the synthetic strategy is an intramolecular Lacey–Dieckmann cyclization reaction

Non-metal-templated approaches to bis(borane) derivatives of macrocyclic dibridgehead diphosphines via alkene metathesis

• Tobias Fiedler,
• Michał Barbasiewicz,
• Michael Stollenz and
• John A. Gladysz

Beilstein J. Org. Chem. 2018, 14, 2354–2365, doi:10.3762/bjoc.14.211

• evolution of synthetic strategies for dibridgehead diphosphorus compounds that employ alkene metathesis. The new approaches (Scheme 2; Scheme 3 and Scheme 5) lack metal templates, which differentiates them from the routes presented in Scheme 1. However, neither is competitive with Scheme 1, despite

Bioinspired cobalt cubanes with tunable redox potentials for photocatalytic water oxidation and CO₂ reduction

• Zhishan Luo,
• Yidong Hou,
• Jinshui Zhang,
• Sibo Wang and
• Xinchen Wang

Beilstein J. Org. Chem. 2018, 14, 2331–2339, doi:10.3762/bjoc.14.208

• possible to develop a Co4O4-based catalyst for reduction applications, such as H2 evolution and CO2 fixation. Herein, we demonstrate that molecular Co4O4 cubanes (Figure 1) are readily and precisely manipulated to tune their redox functions through regulating their electronic structures by ligand

• observed, respectively, which is ascribed to an O2 evolution reaction. The ligand substituted with the electron-withdrawing cyano (CN) group shows the lowest overpotential for water oxidation activities, exhibiting a much higher current density compared to other cubane complexes and Co2+. Meanwhile, we

• O2 gas and CO2-to-CO conversion (Figure 5). For the water oxidation, we have chosen carbon nitride [56][57][58][59][60] coupled with the 1-R molecular complexes to evaluate the oxygen evolution performance. In Figure 5a, without the 1-R molecular complexes, the O2 production rate is rather low (1.2

Tetrathiafulvalene – a redox-switchable building block to control motion in mechanically interlocked molecules

• Hendrik V. Schröder and
• Christoph A. Schalley

Beilstein J. Org. Chem. 2018, 14, 2163–2185, doi:10.3762/bjoc.14.190

• . Evolution of TTF into a key building block in switchable molecular systems After the first syntheses of native TTF in the early 1970s researches quickly noticed the outstanding electronic properties of this molecule [23][39]. One of the first observations with major impact was the unusual conducting

Calix[6]arene-based atropoisomeric pseudo[2]rotaxanes

• Carmine Gaeta,
• Carmen Talotta and
• Placido Neri

Beilstein J. Org. Chem. 2018, 14, 2112–2124, doi:10.3762/bjoc.14.186

• , for the first time, an example of sequence isomerism was reported by Leigh’s group [18], caused by two different flat wheels that can be located differently along a directional thread III and IV (Figure 2). As an evolution of this concept, we envisaged a sequence stereoisomerism if two directional non

Recent advances in materials for organic light emitting diodes

• Eli Zysman-Colman

Beilstein J. Org. Chem. 2018, 14, 1944–1945, doi:10.3762/bjoc.14.168

• technology for the mobile device and display markets. This is largely due to the concerted efforts over the past thirty years to improve the material design, beginning with the first demonstrated viability of this technology in 1987 by Tang and VanSlyke [1]. Emitters in particular have undergone an evolution

Assessing the possibilities of designing a unified multistep continuous flow synthesis platform

• Mrityunjay K. Sharma,
• Roopashri B. Acharya,
• Chinmay A. Shukla and
• Amol A. Kulkarni

Beilstein J. Org. Chem. 2018, 14, 1917–1936, doi:10.3762/bjoc.14.166

• experimental set-ups and even automated self-optimizing platforms were also tested [33]. The natural evolution was an archetype for the multistep flow synthesis. The integration of in-line separation has taken the confidence of the synthesis community one step ahead [21][34][35]. In parallel to this, in-line

• the unified platform (approach 3). However, many unit modules still remain unused (viz., M4, R4, T2–T4, and S6–S14). Table 7 shows the unit module sequences for various products for approach 3. Conclusion For the multistep flow synthesis approach, the next evolution is obviously towards a combination