janvier 2023 – ChemDigest

The Last Fortress of Tin’s Tyranny – Protodenitration of Nitroalkanes

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Methods used for the protodenitration of nitroalkanes were reviewed. Despite several decades of intense research, the most frequently used option remains the Ono-Tanner reaction employing toxic tributyltin hydride. Thus, the protodenitration of nitroalkanes remains the last fortress of the tyranny of tin.

Abstract

Protodenitration, a direct reduction of nitroalkanes to corresponding alkanes, already spans two centuries and is enabled by various reagents. This mini-review provides a historical development of the fundamental transformation and highlights the governing position of the Ono-Tanner reaction employing tributyltin hydride. Due to the unchallenged dominance of the toxic tributyltin hydride and environmentally unpopular solvents sharply contrasting with modern ecological trends, the current situation was dubbed “the last fortress of tin’s tyranny.”

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Dominika Valachová, Michaela Marčeková, Oľga Caletková, Andrej Kolarovič, Pavol Jakubec
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202201341

Colloidosomes as a Protocell Model: Engineering Life‐Like Behaviour through Organic Chemistry

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

The Front Cover illustrates an adapted brightfield microscopy image of colloidosome protocells produced from gold nanoparticles using the Pickering emulsions technique. The artwork highlights the role of organic chemistry in the engineering of colloidosomes with life-like behaviors, which is the subject of this review article. Cover designed by Jun Hyeong Park and Dr. Pierangelo Gobbo. More information can be found in the Review by P. Gobbo et al.

Wiley: European Journal of Organic Chemistry: Table of Contents
Authors: Jun Hyeong Park, Agostino Galanti, India Ayling, Sebastien Rochat, Mark S. Workentin, Pierangelo Gobbo
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/ejoc.202300059

Direct Deprotonative Functionalization of α,α‐Difluoromethyl Ketones using a Catalytic Organosuperbase

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

The deprotonation of α,α-difluoromethyl ketones is underinvestigated due to the instability of the generated carbanion that can evolve into a fluorocarbene. A method for the deprotonative functionalization of these compounds is described herein under an organocatalytic system using various electrophiles, and is also applied to a related α,α-difluoromethyl sulfoxide. This strategy gives access to highly valuable difluoromethylene scaffolds.

Abstract

The deprotonative functionalization of α,α-difluoromethyl ketones is described herein. Using a catalytic organosuperbase and a silane additive, the corresponding difluoroenolate could be generated and trapped with aldehydes to deliver various α,α-difluoro-β-hydroxy ketones in high yields. This new strategy tolerates numerous functional groups and represents the access to the difluoroenolate by direct deprotonation of the difluoromethyl unit. The diastereoselective version of the reaction was also investigated with d.r. up to 93 : 7. Several transformations were performed to demonstrate the synthetic potential of these α,α-difluoro-β-hydroxy ketones. In addition, this method has been extended to the use of other electrophiles such as imines and chalcogen derivatives, and a difluoromethyl sulfoxide as nucleophile, thus leading to a diversity of difluoromethylene compounds.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Amélia Messara, Armen Panossian, Koichi Mikami, Gilles Hanquet, Frédéric R. Leroux
onlinelibrary.wiley.com/doi/10.1002/anie.202215899

ZIF‐8 Nanoparticles Evoke Pyroptosis for High‐Efficiency Cancer Immunotherapy

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

The intrinsic therapeutic effect and immunogenicity of zeolitic imidazolate framework-8 (ZIF-8) nanoparticles were studied. The nanoparticles can intrinsically induce pyroptosis accompanied by necrosis and immunogenic cell death to further activate antitumor immunity and reprogram the immunosuppressive tumor microenvironment, thus realizing high-efficiency immunotherapy and tumor growth inhibition.

Abstract

Although zeolitic imidazolate framework-8 (ZIF-8) has been applied in various tumor therapies, the intrinsic immunogenicity remains unclear. Here, we initiatively discover that ZIF-8 nanoparticles (NPs) can intrinsically induce pyroptosis by a caspase-1/gasdermin D (GSDMD)-dependent pathway. The pyroptotic cell death is accompanied by necrosis and immunogenic cell death (ICD) simultaneously for efficient in situ immunity initiation. Meanwhile, carbonyl cyanide m-chlorophenyl hydrazone (CCCP), a mitochondrial depolarizing agent, is successfully loaded into ZIF-8 NPs and found to further enhance the pyroptosis process. Collectively, the obtained Pluronic F127-modified CCCP-incorporated ZIF-8 NPs (^F127ZIF-8_CCCP NPs) activate antitumor immunity and reprogram immunosuppressive tumor microenvironment (TME), realizing high-efficiency tumor growth inhibition. This work will facilitate biomedicine applications of ZIF-8 and provide good inspiration for pyroptosis-induced cancer therapy.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Binbin Ding, Hao Chen, Jia Tan, Qi Meng, Pan Zheng, Ping’an Ma, Jun Lin
onlinelibrary.wiley.com/doi/10.1002/anie.202215307

Smart Nanosensitizers for Activatable Sono‐Photodynamic Immunotherapy of Tumors by Redox‐Controlled Disassembly

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Tumor-targeted and glutathione (GSH)-activatable nanosensitizers (1-NPs) are fabricated via co-assembly and disassembly processes, which confer burst release of small molecules 2-Gd, Zn-PPA-SH and NLG919 within tumor cells, enabling fluorescence and magnetic resonance bimodal imaging-guided sono-photodynamic immunotherapy of orthotopic 4T1 breast tumors and deep-seated GL261 gliomas in mice upon irradiation with combined ultrasound (US) and 671-nm laser (hv).

Abstract

Tumor-targeted and stimuli-activatable nanosensitizers are highly desirable for cancer theranostics. However, designing smart nanosensitizers with multiple imaging signals and synergistic therapeutic activities switched on is challenging. Herein, we report tumor-targeted and redox-activatable nanosensitizers (1-NPs) for sono-photodynamic immunotherapy of tumors by molecular co-assembly and redox-controlled disassembly. 1-NPs show a high longitudinal relaxivity (r₁=18.7±0.3 mM⁻¹ s⁻¹), but “off” dual fluorescence (FL) emission (at 547 and 672 nm), “off” sono-photodynamic therapy and indoleamine 2,3-dioxygenase 1 (IDO1) inhibition activities. Upon reduction by glutathione (GSH), 1-NPs rapidly disassemble and remotely release small molecules 2-Gd, Zn-PPA-SH and NLG919, concurrently switching on (1) dual FL emission, (2) sono-photodynamic therapy and (3) IDO1 inhibition activities. After systemic injection, 1-NPs are effective for bimodal FL and magnetic resonance (MR) imaging-guided sono-photodynamic immunotherapy of orthotropic breast and brain tumors in mice under combined ultrasound (US) and 671-nm laser irradiation.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Lingjun Liu, Junya Zhang, Ruibing An, Qi Xue, Xi Cheng, Yuxuan Hu, Zheng Huang, Luyan Wu, Wenhui Zeng, Yinxing Miao, Jie Li, Yu Zhou, Hong‐Yuan Chen, Hong Liu, Deju Ye
onlinelibrary.wiley.com/doi/10.1002/anie.202217055

Isolation of an Annulated 1,4‐Distibabenzene Diradicaloid

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

The 1,4-distibabenzene-1,4-diide (cyclic bis-stibinidene) compound 5 is isolated as a crystalline solid. 5 undergoes 2e-oxidation to the dicationic compound (6)²⁺, which can be reduced back to 5. The broken-symmetry open-shell singlet solution for (6)²⁺ is calculated to be 2.13 kcal mol⁻¹ more stable than the closed-shell singlet solution. (6)⁺² is stabilized by the delocalization of unpaired electrons over the benzenoid C₄Sb₂ ring and has 39 % diradical character.

Abstract

The first 1,4-distibabenzene-1,4-diide compound [(ADC)Sb]₂ (5) based on an anionic dicarbene (ADC) (ADC=PhC{N(Dipp)C}₂, Dipp=2,6-iPr₂C₆H₃) is reported as a bordeaux-red solid. Compound 5, featuring a central six-membered C₄Sb₂ ring with formally Sb^I atoms may be regarded as a base-stabilized cyclic bis-stibinidene in which each of the Sb atoms bears two lone-pairs of electrons. 5 undergoes 2 e-oxidation with Ph₃C[B(C₆F₅)₄] to afford [(ADC)Sb]₂[B(C₆F₅)₄]₂ (6) as a brick-red solid. Each of the Sb atoms of 6 has an unpaired electron and a lone-pair. The broken-symmetry open-shell singlet diradical solution for (6)²⁺ is calculated to be 2.13 kcal mol⁻¹ more stable than the closed-shell singlet. The diradical character of (6)²⁺ according to SS-CASSCF (state-specific complete active space self-consistent field) and UHF (unrestricted Hartree-Fock) methods amounts to 36 % and 39 %, respectively. Treatments of 6 with (PhE)₂ yield [(ADC)Sb(EPh)]₂[B(C₆F₅)₄]₂ (7-E) (E=S or Se). Reaction of 5 with (cod)Mo(CO)₄ affords [(ADC)Sb]₂Mo(CO)₄ (8).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Henric Steffenfauseweh, Dennis Rottschäfer, Yury V. Vishnevskiy, Beate Neumann, Hans‐Georg Stammler, Dariusz W. Szczepanik, Rajendra S. Ghadwal
onlinelibrary.wiley.com/doi/10.1002/anie.202216003

Electron Spin Catalysis with Graphene Belts

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Graphene belts with high electron spin concentrations, which were synthesized by C(sp²)−C(sp²) radical coupling, act as aerobic spin catalysts for both the oxygen reduction reaction (ORR) and a benzylamine coupling with molecular oxygen to generate the corresponding imine; the catalytic mechanism has been studied by electron spin resonance spectroscopy.

Abstract

Here, we report kinetic studies using electron spin resonance spectroscopy on spin catalysis reactions caused by using graphene belts which were synthesized by a radical coupling method. The results show that σ-type free radical species provide the dominant sites for catalytic activity through the spin-spin interaction, although there are some other influencing factors. The spin catalysis mechanism can be applied both in the oxygen reduction reaction (ORR) and in organic synthesis. The graphene belt spin catalyst shows excellent performance with a high ORR half-wave potential of 0.81 V and long-term stability with almost no loss of activity after 50 000 cycles in alkaline media. It also shows excellent performance in a benzylamine coupling with molecular oxygen to generate the corresponding imine at an average conversion of ≈97.7 % and an average yield of ≈97.9 %. This work opens up a new research direction for understanding aerobic processes in the field of spin catalysis.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Yulan Tian, Huaqiang Cao, Haijun Yang, Wenqing Yao, Jiaou Wang, Zirui Qiao, Anthony K. Cheetham
onlinelibrary.wiley.com/doi/10.1002/anie.202215295

Selective Separation of Lithium, Magnesium and Calcium using 4‐Phosphoryl Pyrazolones as pH‐Regulated Receptors

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Stepwise separation of Ca²⁺, Mg²⁺ and Li⁺ has been achieved by liquid-liquid extraction employing a series of advanced 4-phosphoryl pyrazolone ligands together with TOPO (trioctylphosphine oxide) as co-ligand via pH regulation. X-ray crystal structure determinations of selected complexes revealed diverse binding modes across all three metal species.

Abstract

Ensuring continuous and sustainable lithium supply requires the development of highly efficient separation processes such as LLE (liquid-liquid extraction) for both primary sources and certain waste streams. In this work, 4-phosphoryl pyrazolones are used in an efficient pH-controlled stepwise separation of Li⁺ from Ca²⁺, Mg²⁺, Na⁺ and K⁺. The factors affecting LLE process, such as the substitution pattern of the extractant, diluent/water distribution, co-ligand, pH, and speciation of the metal complexes involved, were systematically investigated. The maximum extraction efficiency of Li⁺ at pH 6.0 was 94 % when Mg²⁺ and Ca²⁺ were previously separated at pH<5.0, proving that the separation of these ions is possible by simply modulating the pH of the aqueous phase. Our study points a way to separation of lithium from acid brine or from spent lithium ion battery leaching solutions, which supports the future supply of lithium in a more environmentally friendly and sustainable manner.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Jianfeng Zhang, Narisara Tanjedrew, Marco Wenzel, Philipp Royla, Hao Du, Supavadee Kiatisevi, Leonard F. Lindoy, Jan J. Weigand
onlinelibrary.wiley.com/doi/10.1002/anie.202216011

Electron‐Rich Oxycarbenes: New Synthetic and Catalytic Applications beyond Group 6 Fischer Carbene Complexes

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Oxycarbenes have emerged as useful intermediates in synthetic chemistry. This Minireview summarizes early synthetic and catalytic applications of late-transition-metal oxycarbene complexes and highlights recent advances in free oxycarbene reactions and transition-metal-catalyzed reactions involving oxycarbenes.

Abstract

Oxycarbenes have emerged as useful intermediates in synthetic chemistry. Compared to the widely studied oxycarbene metal complexes bearing Group 6 metals, the synthetic and catalytic applications of oxycarbenes beyond Group 6 Fischer carbene complexes are less explored because of the difficulty in controlling their reactivity and the need to use a stoichiometric amount of a presynthesized Group 6 metal carbene complex as the starting material. This Minireview summarizes early synthetic and catalytic applications of late-transition-metal oxycarbene complexes and highlights recent advances in free oxycarbene reactions and transition-metal-catalyzed reactions involving oxycarbenes. We hope this Minireview will inspire further developments in this emerging area.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Gang Zhou, Zhuanzhuan Guo, Xiao Shen
onlinelibrary.wiley.com/doi/10.1002/anie.202217189

Expanded Conformations of Monomeric Tau Initiate Its Amyloidogenesis

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Single-molecule analysis of tau shows that pro-amyloidogenic mutations and chemical environment shift the monomeric conformational landscape towards expanded conformers, exposing amyloidogenic hexapeptides. The chemical environment also originates structural rearrangements, which may be behind the polymorphic amyloid structures found across tauopathies. Conversely, anti-amyloidogenic factors promote the formation of collapsed conformers with a specific inert structure.

Abstract

Understanding early amyloidogenesis is key to rationally develop therapeutic strategies. Tau protein forms well-characterized pathological deposits but its aggregation mechanism is still poorly understood. Using single-molecule force spectroscopy based on a mechanical protection strategy, we studied the conformational landscape of the monomeric tau repeat domain (tau-RD_244-368). We found two sets of conformational states, whose frequency is influenced by mutations and the chemical context. While pathological mutations Δ280K and P301L and a pro-amyloidogenic milieu favored expanded conformations and destabilized local structures, an anti-amyloidogenic environment promoted a compact ensemble, including a conformer whose topology might mask two amyloidogenic segments. Our results reveal that to initiate aggregation, monomeric tau-RD_244-368 decreases its polymorphism adopting expanded conformations. This could account for the distinct structures found in vitro and across tauopathies.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: María del Carmen Fernández‐Ramírez, Kevin Kan‐Shing Ng, Margarita Menéndez, Douglas V. Laurents, Rubén Hervás, Mariano Carrión‐Vázquez
onlinelibrary.wiley.com/doi/10.1002/anie.202209252

Spectroscopic Identification of Diphosphene HPPH and Isomeric Diphosphinyldene PPH2

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

The simplest diphosphene HPPH (cis and trans conformers) and diphosphinyldene PPH₂ have been generated and spectroscopically characterized in solid N₂– and Ar-matrices at 10 K. In addition to the photo-induced conversion of these P₂H₂ isomers, the prototype phosphorus-phosphorus multiple bonding properties have been disclosed.

Abstract

The simplest diphosphene HPPH and isomeric diphosphinyldene PPH₂ features prototype phosphorus-phosphorus multiple bonding properties that have been of long-standing interest in main-group chemistry. Herein, we report the observation of cis-HPPH, trans-HPPH, and PPH₂ among the respective laser photolysis products of phosphine (PH₃) and diphosphine (P₂H₄) in solid N₂– and Ar-matrices at 10 K. The identification of these P₂H₂ isomers with matrix-isolation IR and UV/Vis spectroscopy is supported by D-isotope labeling and the quantum chemical calculations at the CCSD(T)-F12a/cc-pVTZ-F12 level using configuration-selective vibrational configuration interaction theory (VCI). Bonding analyses suggest that the two conformers of HPPH contain standard PP double bonds, whereas, PPH₂ resembles P₂ in having partial PP triple bond due to the H₂P←P π bonding interaction.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Bo Lu, Lina Wang, Xin Jiang, Guntram Rauhut, Xiaoqing Zeng
onlinelibrary.wiley.com/doi/10.1002/anie.202217353

Hydrogen Bonds Strengthened Metal‐Free Perovskite for Degradable X‐ray Detector with Enhanced Stability, Flexibility and Sensitivity

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

This work first designed and synthesized metal-free MPAZE-NH₄I₃ ⋅ H₂O perovskites by introducing bulk methyl groups to improve tolerance factor and enhance hydrogen bonds for improving its stability and performance. Importantly, the related flexible X-ray detector shows the highest sensitivity of 740.8 μC Gy_air⁻¹ cm⁻², and promises to realize non-toxic degradation, mechanical bending stability and array imaging for future application.

Abstract

Metal-free perovskites (MFPs) with flexible and degradable properties have been adopted in flexible X-ray detection. For now, figuring out the key factors between structure and device performance are critical to guide the design of MFPs. Herein, MPAZE-NH₄I₃ ⋅ H₂O was first designed and synthesized with improved structural stability and device performance. Through theoretical calculations, the introducing methyl group benefits modulating tolerance factor, increases dipole moment and strengthens hydrogen bonds. Meanwhile, H₂O increases the hydrogen bond formation sites and synergistically realizes the band nature modulation, ionic migration inhibition and structural stiffness optimization. Spectra analysis also proves that the improved electron-phonon coupling and carrier recombination lifetime contribute to enhanced performance. Finally, a flexible and degradable X-ray detector was fabricated with the highest sensitivity of 740.8 μC Gy_air⁻¹ cm⁻² and low detection limit (0.14 nGy_air s⁻¹).

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Zhizai Li, Guoqiang Peng, ZhenHua Li, Youkui Xu, Tao Wang, Haoxu Wang, Zitong Liu, Gang Wang, Liming Ding, Zhiwen Jin
onlinelibrary.wiley.com/doi/10.1002/anie.202218349

Oral Anticancer Heterobimetallic PtIV−AuI Complexes Show High In Vivo Activity and Low Toxicity

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Oral anticancer heterobimetallic Pt^IV−Au^IN-heterocyclic carbene complexes with a dual mechanism of action show high potency with low toxicity in vivo. The conjugation of two metals results in an enhanced inhibitory effect towards thioredoxin reductase and facilitates the co-transport of the prodrug into the tumor before activation.

Abstract

Au^I-carbene and Pt^IV−Au^I-carbene prodrugs display low to sub-μM activity against several cancer cell lines and overcome cisplatin (cisPt) resistance. Linking a cisPt-derived Pt^IV(phenylbutyrate) complex to a Au^I-phenylimidazolylidene complex 2, yielded the most potent prodrug. While in vivo tests against Lewis Lung Carcinoma showed that the prodrug Pt^IV(phenylbutyrate)-Au^I-carbene (7) and the 1 : 1 : 1 co-administration of cisPt: phenylbutyrate:2 efficiently inhibited tumor growth (≈95 %), much better than 2 (75 %) or cisPt (84 %), 7 exhibited only 5 % body weight loss compared to 14 % for 2, 20 % for cisPt and >30 % for the co-administration. 7 was much more efficient than 2 at inhibiting TrxR activity in the isolated enzyme, in cells and in the tumor, even though it was much less efficient than 2 at binding to selenocysteine peptides modeling the active site of TrxR. Organ distribution and laser-ablation (LA)-ICP-TOFMS imaging suggest that 7 arrives intact at the tumor and is activated there.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Tomer Babu, Hiba Ghareeb, Uttara Basu, Hemma Schueffl, Sarah Theiner, Petra Heffeter, Gunda Koellensperger, Norman Metanis, Valentina Gandin, Ingo Ott, Claudia Schmidt, Dan Gibson
onlinelibrary.wiley.com/doi/10.1002/anie.202217233

Monitoring Photoinduced Interparticle Chemical Communication In Situ

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

In situ monitoring of photoinduced chemical communication between single Ag nanoparticles is achieved via the stochastic collision electrochemistry. The superior sensitivity enables to investigate the dynamic chemical potential difference at the single-nanoparticle level, indicating the cooperative interparticle communication controls the morphology transformation kinetics, thereby determining the final structure of collective Ag nanoparticles.

Abstract

Monitoring interparticle chemical communication plays a critical role in the nanomaterial synthesis as this communication controls the final structure and stability of global nanoparticles (NPs). Yet most ensemble analytical techniques, which could only reveal average macroscopic information, are unable to elucidate NP-to-NP interactions. Herein, we employ stochastic collision electrochemistry to track the morphology transformation of Ag NPs in photochemical process at the single NP level. By further statistical analysis of time-resolved current transients, we quantitatively determine the dynamic chemical potential difference and interparticle communication between populations of large and small Ag NPs. The high sensitivity of stochastic collision electrochemistry enables the in situ investigation of chemical communication-dependent transformation kinetics of NPs in photochemical process, shedding light on designing nanomaterials.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Mengjie Chen, Si‐Min Lu, Hao‐Wei Wang, Yi‐Tao Long
onlinelibrary.wiley.com/doi/10.1002/anie.202215631

Designed Iron Catalysts for Allylic C−H Functionalization of Propylene and Simple Olefins

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

A new cyclopentadienyliron dicarbonyl complex was discovered to enable the coupling of the allylic carbon of propylene and carbonyl electrophiles. This approach was also successfully applied to allylic C−H functionalization of simple olefins. Experimental and computational studies provided insights into the mechanism and origins of ligand effects on reactivity and diastereoselectivity.

Abstract

Propylene gas is produced worldwide by steam cracking on million-metric-ton scale per year. It serves as a valuable starting material for π-bond functionalization but is rarely applied in transition metal-catalyzed allylic C−H functionalization for fine chemical synthesis. Herein, we report that a newly-developed cationic cyclopentadienyliron dicarbonyl complex allows for the conversion of propylene to its allylic C−C bond coupling products under catalytic conditions. This approach was also found applicable to the allylic functionalization of simple α-olefins with distinctive branched selectivity. Experimental and computational mechanistic studies supported the allylic deprotonation of the metal-coordinated alkene as the turnover-limiting step and led to insights into the multifaceted roles of the newly designed ligand in promoting allylic C−H functionalization with enhanced reactivity and stereoselectivity.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Ruihan Wang, Yidong Wang, Ruiqi Ding, Parker B. Staub, Christopher Z. Zhao, Peng Liu, Yi‐Ming Wang
onlinelibrary.wiley.com/doi/10.1002/anie.202216309

Allosteric Regulation of Aptamer Affinity through Mechano‐Chemical Coupling

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

We describe a simple and effective strategy for reversibly fine-tuning aptamer affinity by an allosteric molecular clamp that perturbs aptamer folding through mechanical extension, forcing it into a state in which its binding competency is considerably reduced. Aptamer affinity is regulated by tuning the mechanical properties of the molecular clamp.

Abstract

The capacity to precisely modulate aptamer affinity is important for a wide variety of applications. However, most such engineering strategies entail laborious trial-and-error testing or require prior knowledge of an aptamer’s structure and ligand-binding domain. We describe here a simple and generalizable strategy for allosteric modulation of aptamer affinity by employing a double-stranded molecular clamp that destabilizes aptamer secondary structure through mechanical tension. We demonstrate the effectiveness of the approach with a thrombin-binding aptamer and show that we can alter its affinity by as much as 65-fold. We also show that this modulation can be rendered reversible by introducing a restriction enzyme cleavage site into the molecular clamp domain and describe a design strategy for achieving even more finely-tuned affinity modulation. This strategy requires no prior knowledge of the aptamer’s structure and binding mechanism and should thus be generalizable across aptamers.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Hao Qu, Manyi Zheng, Qihui Ma, Lu Wang, Yu Mao, Michael Eisenstein, Hyongsok Tom Soh, Lei Zheng
onlinelibrary.wiley.com/doi/10.1002/anie.202214045

Visible‐Light‐Mediated Controlled Radical Branching Polymerization in Water

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

A water-soluble inibramer, sodium 2-bromoacrylate, triggered branching during photoinduced atom transfer radical polymerization of methacrylate monomers in the open air. As a result, well-defined branched polymers with controlled molecular weights, degrees of branching, and low dispersity values were obtained in water. The radical branching polymerization also exhibited spatial control and enabled the synthesis of branched polymer bioconjugates.

Abstract

Hyperbranched polymethacrylates were synthesized by green-light-induced atom transfer radical polymerization (ATRP) under biologically relevant conditions in the open air. Sodium 2-bromoacrylate (SBA) was prepared in situ from commercially available 2-bromoacrylic acid and used as a water-soluble inibramer to induce branching during the copolymerization of methacrylate monomers. As a result, well-defined branched polymethacrylates were obtained in less than 30 min with predetermined molecular weights (36 000<M_n<170 000), tunable degree of branching, and low dispersity values (1.14≤Đ≤1.33). Moreover, the use of SBA inibramer enabled the synthesis of bioconjugates with a well-controlled branched architecture.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Kriti Kapil, Grzegorz Szczepaniak, Michael R. Martinez, Hironobu Murata, Arman Moini Jazani, Jaepil Jeong, Subha R. Das, Krzysztof Matyjaszewski
onlinelibrary.wiley.com/doi/10.1002/anie.202217658

Biotechnological Frontiers of DNA Nanomaterials Continue to Expand: Bacterial Infection using Virus‐Inspired Capsids

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Through the engineering of virus-inspired DNA-origami particles loaded with natural bacteriophage genomic cargo; scientists measured a retained functional infection in non-competent bacterial cells. Critical parameters for infectivity include structural rigidity and complete yet dynamic loading of the cargo through multivalent optimization of anchors.

Abstract

The elegant geometry of viruses has inspired bio-engineers to synthetically explore the self-assembly of polyhedral capsids employed to protect new cargo or change an enzymatic microenvironment. Recently, Yang and co-workers used DNA nanotechnology to revisit the icosahedral capsid structure of the phiX174 bacteriophage and reloaded the original viral genome as cargo into their fully synthetic architecture. Surprisingly, when using a favorable combination of structural rigidity and dynamic multivalent cargo entrapment, the synthetic particles were able to infect non-competent bacterial cells and produce the original phiX174 bacteriophage. This work presents an exciting new direction of DNA nanotech for bio-engineering applications which involve bacterial interactions.

Wiley: Angewandte Chemie International Edition: Table of Contents
Authors: Maartje M. C. Bastings
onlinelibrary.wiley.com/doi/10.1002/anie.202218334

Molecular Design of A−D−A Electron Acceptors Towards Low Energy Loss for Organic Solar Cells

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Electron-vibration coupling is an important factor affecting the energy loss of organic solar cells. Enhancing molecular planarity and rigidity, adopting angular fusion mode, and tuning electron-deficient core can effectively decrease the electron-vibration couplings of A−D−A electron acceptors to achieve efficient charge generation and low energy loss for organic photovoltaics.

Abstract

Low energy loss is a prerequisite for organic solar cells to achieve high photovoltaic efficiency. Electron-vibration coupling (i. e., intramolecular reorganization energy) plays a crucial role in the photoelectrical conversion and energy loss processes. In this Concept article, we summarize our recent theoretical advances on revealing the energy loss mechanisms at the molecular level of A−D−A electron acceptors. We underline the importance of electron-vibration couplings on reducing the energy loss and describe the effective molecular design strategies towards low energy loss through decreasing the electron-vibration couplings.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Yuan Guo, Lingyun Zhu, Ruihong Duan, Guangchao Han, Yuanping Yi
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203356

Enhanced Photocatalytic Activity of Hyper‐Cross‐Linked Polymers Toward Amines Oxidation Coupled with H2O2 Generation through Extending Monomer’s Conjugation Degree

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Extending the monomer’s conjugation degree of HCPs photocatalysts could significantly promote the separation and transfer efficiency of photogenerated carriers. QP-HCPs bring out the best photocatalytic activity for amines oxidation coupled with H₂O₂ generation due to its maximum monomer’s conjugation degree and excellent O₂ adsorption capacity.

Abstract

Visible-light-driven amines oxidation coupled with hydrogen peroxide (H₂O₂) generation is a promising way to convert solar energy to chemical energy. Herein, a series of hyper-cross-linked polymers (HCPs) photocatalysts with different arenes monomers, including benzene (BE), diphenyl (DP), p-terphenyl (TP), or p-quaterphenyl (QP), were synthesized by simple Friedel–Crafts alkylation reaction. Owing to the maximum monomer’s conjunction degree and excellent oxygen (O₂) adsorption capacity, QP-HCPs exhibited highest photocatalytic activity for benzylamine oxidation coupled with H₂O₂ generation under the irradiation of 455 nm Blue LED lamp. More than 99 % of benzylamine could be converted to N-benzylidenebenzylamine within 60 min. In addition, nearly stoichiometric H₂O₂ was synchronously obtained with a high production rate of 9.3 mmol g_cat⁻¹ h⁻¹. Our work not only demonstrated that the photocatalytic activity of HCPs photocatalysts significantly depends on monomer’s conjunction degree, but also provided a new strategy for converting solar energy to chemical energy.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Xinhao Nie, Ying Zhao, Wei Gao, Weihua Liu, Xiang Cheng, Yongjun Gao, Ningzhao Shang, Shutao Gao, Chun Wang
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203607

The Chelate Effect Rationalizes Observed Rate Acceleration and Enantioselectivity in BINOL‐Catalyzed Petasis Reactions

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

1,1′-Bi-2-naphthol (BINOL) induces high enantiomeric excess of Petasis reaction by forming cyclic B(IV)BINOL intermediates. The chelate formation results in an extraordinary reaction rate acceleration and in the diminishment of the racemic background reaction. An unusual iminium C−H and O-BINOL hydrogen bond is responsible for the stereoselectivity. Formation of a cyclic trigonal B(III)BINOL byproduct accompanying the product enables the BINOL catalyst turnover.

Abstract

Density functional theory (DFT) calculations afforded insight into the origin of the experimentally observed reaction rate acceleration (≥500 fold) and enantioselectivity (≥99 % ee) of 1,1′-bi-2-naphthol- (BINOL-) catalyzed three-component Petasis reactions . BINOL accelerates the rate determining step by forming a B^IV chelate, which involves the loss of water from the hemiaminal moiety to generate an iminium intermediate. Subsequent vinyl group transfer from B^IV to the iminium carbon affords the enantiomerically enriched product and a cyclic trigonal B(III)BINOL complex, which rapidly releases the BINOL allowing it to re-enter the catalytic cycle. In the transition state of the vinyl transfer step, C−H−O hydrogen bonding between the iminium C−H and O of (R)-BINOL directs the vinyl group addition to the Re-face of the iminium carbon. This mechanism explains both the rate acceleration and high enantioselectivity of the stereo determining step.

Wiley: Chemistry – A European Journal: Table of Contents
Authors: Fredrik Haeffner, Thomas C. Pickel, April Hou, Donald G. Walker, William F. Kiesman, Xianglin Shi
chemistry-europe.onlinelibrary.wiley.com/doi/10.1002/chem.202203331

Advances in Exploring Cyclopentadienyl (Cp) Rhodium Catalysts Featuring Diastereotopic or Enantiotopic Cp Faces for Asymmetric C–H Activation

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Synthesis
DOI: 10.1055/a-2005-5006

Chiral cyclopentadienyl rhodium (CpRh) complexes have emerged as a class of powerful catalysts for enantioselective C–H activation reactions. In terms of Cp ligand development, the mainstream is to design chiral ligands with C 2 symmetry in order to avoid the problem of Cp face selectivity during their metalation with rhodium. In recent years, CpRh catalysts with diastereotopic or enantiotopic Cp faces were also revealed and successfully applied in asymmetric C–H activation. These advances are summarized in this short review together with perspectives for their future development.1 Introduction2 Cp Ligands with Diastereotopic Cp Faces3 Cp Ligands with Enantiotopic Cp Faces4 Conclusion and Outlook
[…]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents | Abstract | Full text

Synthesis
Authors: Yan, Xiaoqiang
dx.doi.org/10.1055/a-2005-5006

Silver-Catalyzed Ring Expansion of Activated N-Heteroarenes via 1,4-Dearomative Addition of Diazomethylphosphonates

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Synthesis
DOI: 10.1055/a-2004-1279

Phosphorus-containing N-heterocycles are important molecular motifs due to their unique structural features and biological activities. In this study, we developed a silver-catalyzed reaction for the construction of phosphorus-containing azepine derivatives via a domino-type dearomatization procedure, followed by ring expansion. In addition, diazomethylphosphonates were employed for the first time as nucleophiles in the 1,4-dearomative addition of activated N-heteroarenes, furnishing cyclopropane-fused piperidine intermediates that were readily restructured into their corresponding azepine derivatives. The reactivities of the diazomethylphosphonates in the developed dearomatization strategy were found to be superior to those of other diazo compounds, thereby resulting in the generation of the desired seven-membered N-heterocycles within a very short reaction time.
[…]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents | Abstract | Full text

Synthesis
Authors: Baek, Sekwang
dx.doi.org/10.1055/a-2004-1279

Synthesis of 2-Alkyl-2-(2-furanyl)-1,3-cyclopentanediones

Par admin / 31 janvier 2023 31 janvier 2023 / Non classé

Synthesis
DOI: 10.1055/a-2004-1333

2,2-Disubstituted 1,3-cyclopentanediones are versatile building blocks for synthesizing complex natural products with bicyclic structures including cyclopentane rings. The reported method for the synthesis of these compounds involves the semi-pinacol rearrangement of a Mukaiyama aldol adduct prepared from a ketone/ketal and 1,2-bis(trimethylsilyloxy)cyclobutene. However, the adoption of α-oxy-functionalized ketones/ketals is quite difficult, as demonstrated by our experiments. To overcome this limitation of the method, 2-acylfuran derivatives were used as the reactants to synthesize 2,2-disubstituted 1,3-cyclopentanediones. Furthermore, two reaction conditions, that is, the use of 1.4 equivalents of a boron trifluoride-diethyl ether complex or 0.4 and 0.2 equivalent of trimethylsilyl triflate and methoxytrimethylsilane, respectively, were established for the conversion of 2-acylfurans into the corresponding 1,3-cyclopentanediones in acceptable yields. The transformations of the furan rings in the obtained products were also investigated.
[…]

Georg Thieme Verlag KG Rüdigerstraße 14, 70469 Stuttgart, Germany

Article in Thieme eJournals:
Table of contents | Abstract | Full text

Synthesis
Authors: Ikeuchi, Kazutada
dx.doi.org/10.1055/a-2004-1333

Synthesis and characterization of degradation impurities of Flucloxacillin and Dicloxacillin

Par admin / 31 janvier 2023 31 janvier 2023 / heterocycles

Degrdation impurities of Flucloxacillin & Dicloxacillin.

Abstract

A series of degradation impurities of Flucloxacillin and Dicloxacillin were synthesized. The formation and a facile synthesis of each impurity were presented in detail, namely penicilloic acids of Dicloxacillin (3) (Ph.Eur. Impurity-A), Dicloxacillin glycine analog (4), Dicloxacillin penilloic acids (5) (Ph.Eur. Impurity-B), Dicloxacillin Pencillamide (6), N-Acetylated penicilloic acid of Dicloxacillin (7), DCMICAA adduct of Dicloxacillin penicilloic acid (8), Flucloxacillin glycine analog (Ph.Eur. Impurity-F) (9), penicilloic acids of Flucloxacillin (10), penilloic acids of Flucloxacillin (11), CFMICAA adduct of Flucloxacillin penicilloic acid (Flucloxacillin Ph.Eur. Impurity-H) (12), Flucloxacillin Penicillamide (Flucloxacillin Ph.Eur. Impurity-E) (13), and N-Acetylated penicilloic acid of Flucloxacillin (14). These impurities are extensively characterized by various analytical techniques.

Mois : janvier 2023

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