Conspectus Axially chiral compounds have received much attention from chemists because of their widespread appearance in natural products, biologically active compounds, and useful chiral ligands in ...asymmetric catalysis. Because of the importance of this structural motif, the catalytic enantioselective construction of axially chiral scaffolds has been intensively investigated, and great progress has been accomplished. However, the majority of methodologies in this field focus on the use of metal catalysis, whereas approaches involving organocatalysis have started to emerge only recently. This Account describes certain advances in the organocatalytic asymmetric synthesis of axially chiral compounds involving the following strategies: kinetic resolution, desymmetrization, cyclization/addition, direct arylation, and so on. We began our investigation by developing a highly efficient strategy for the kinetic resolution of axially chiral BINAM derivatives involving a chiral Brønsted acid-catalyzed imine formation and transfer hydrogenation cascade process, thereby providing a convenient route to generate chiral BINAM derivatives in high yields with excellent enantioselectivities. The desymmetrization of 1-aryltriazodiones (ATADs) through an organocatalyzed tyrosine clicklike reaction wherein a nucleophile was added to the ATAD afforded an interesting type of axially chiral N-arylurazole in an excellent remote enantiocontrolled manner. We then focused on a direct construction strategy involving cyclization and the addition strategy given the inherent limitations of the kinetic resolution in terms of the chemical yield and the desymmetrization in terms of the substrate scope. By utilizing the catalytic enantioselective Paal–Knorr reaction, we disclosed a general and efficient cyclization method to access enantiomerically pure arylpyrroles. The direct heterocycle formation and the stepwise method, which was executed in a one-pot fashion containing enantioselective cyclization and subsequent aromatization, were successfully applied for the construction of diverse axially chiral arylquinazolinones catalyzed by chiral Brønsted acids. We discovered the asymmetric organocatalytic approach to construct axially chiral styrenes through the 1,4-addition of arylalkynals in good chemical yields and enantioselectivities. Such structural motifs are important precursors for further transformations into biologically active compounds and useful synthetic intermediates and may have potential applications in asymmetric syntheses as olefin ligands or organocatalysts. To further tackle this challenge, we accomplished the phosphoric acid-catalyzed enantioselective direct arylative reactions of 2-naphthol and 2-naphthamine with quinone derivatives to deliver efficient access to a class of axially chiral BINOL and NOBIN derivatives in good yields with excellent enantioselectivities under mild reaction conditions. Most importantly, we discovered that the azo group can effectively perform as a directing and activating group for organocatalytic formal aryl C–H functionalization via formal nucleophilic aromatic substitution of azobenzene derivatives. Thus, a wide range of axially chiral arylindoles were synthesized in good yields with excellent enantioselectivities. We anticipate that this strategy will foster the development of many other transformations and motivate a new enthusiasm for organocatalytic enantioselective aryl functionalization. Moreover, SPINOLs are fundamental synthetic precursors in the construction of other chiral organocatalysts and ligands. We have successfully developed a phosphoric acid-catalyzed enantioselective approach for SPINOLs. This approach is highly convergent and functional-group-tolerant for the efficient generation of SPINOLs with good results, thus delivering practical access to this privileged structure.
The aim of this study was to analyze the clinical data, discharge rate, and fatality rate of COVID‐19 patients for clinical help. The clinical data of COVID‐19 patients from December 2019 to February ...2020 were retrieved from four databases. We statistically analyzed the clinical symptoms and laboratory results of COVID‐19 patients and explained the discharge rate and fatality rate with a single‐arm meta‐analysis. The available data of 1994 patients in 10 literatures were included in our study. The main clinical symptoms of COVID‐19 patients were fever (88.5%), cough (68.6%), myalgia or fatigue (35.8%), expectoration (28.2%), and dyspnea (21.9%). Minor symptoms include headache or dizziness (12.1%), diarrhea (4.8%), nausea and vomiting (3.9%). The results of the laboratory showed that the lymphocytopenia (64.5%), increase of C‐reactive protein (44.3%), increase of lactic dehydrogenase (28.3%), and leukocytopenia (29.4%) were more common. The results of single‐arm meta‐analysis showed that the male took a larger percentage in the gender distribution of COVID‐19 patients 60% (95% CI 0.54, 0.65), the discharge rate of COVID‐19 patients was 52% (95% CI 0.34,0.70), and the fatality rate was 5% (95% CI 0.01,0.11).
Research Highlights
Our study explored the clinical and epidemiological characteristics of COVID‐19 patients, and proposed the need to focus on other systemic symptoms such as the gastrointestinal tract firstly, which could be of use for clinical work.
Background/Aims
Long noncoding RNAs (lncRNAs) have been demonstrated to serve distinct roles in human tumorigenesis. Previous studies have found that lncRNA small nucleolar RNA host gene 4 (SNHG4) ...was dysregulated in several tumors. However, the expression, clinical significances, and action mechanisms of SNHG4 in prostate cancer (PCa) are still unclear.
Methods
Quantitative real‐time polymerase chain reaction (qRT‐PCR) was utilized to detect SNHG4 expression in tissue samples and PCa cells. Cell counting kit‐8, 5‐ethynyl‐2′‐deoxyuridine, clonogenic formation, wound‐healing, and transwell invasion assays were, respectively, used to evaluate cell proliferation, colony formation ability, migration, and invasion. Flow cytometric analysis was applied to assess cell apoptosis. Chromatin immunoprecipitation assays were conducted to determine the binding between SP1 and SNHG4 promoter. Luciferase reporter assay, qRT‐PCR, and western blot analysis were carried out to explore and confirm the interaction among SNHG4, miR‐377, and ZIC5.
Results
SNHG4 was highly expressed in PCa and its upregulation was induced by transcription factor SP1. The high levels of SNHG4 were distinctly associated with tumor stage, lymph node metastasis, and reduced overall survival of patients with PCa. SNHG4 knockdown inhibited the growth, migration, and invasion of PCa cells. In addition, miR‐377 was a target of SNHG4 and ZIC5 was a target gene of miR‐377 in PCa. SNHG4 promoted ZIC5‐mediated growth and metastasis through modulating miR‐377.
Conclusion
Our findings illuminate how SNHG4 formed a regulatory network to display a tumor‐promotive effect in PCa and revealed that SNHG4 may be a novel therapeutic target and prognostic marker for patients with PCa.
Our findings illuminate how SNHG4 formed a regulatory network to display a tumor‐promotive effect in PCa and revealed that SNHG4 may be a novel therapeutic target and prognostic marker for patients with PCa.
To assess the responses to taper in endurance athletes using meta-analysis.
Systematic searches were conducted in China National Knowledge Infrastructure, PubMed, Web of Science, SPORTDiscus, and ...EMBASE databases. Standardized mean difference (SMD) and 95% confidence interval (CI) of outcome measures were calculated as effect sizes.
14 studies were included in this meta-analysis. Significant improvements were found between pre- and post-tapering in time-trial (TT) performance (SMD = -0.45; P < 0.05) and time to exhaustion (TTE) performance (SMD = 1.28; P < 0.05). However, There were no improvements in maximal oxygen consumption (Formula: see text) and economy of movement (EM) (P > 0.05) between pre- and post-tapering. Further subgroup analysis showed that tapering combined with pre-taper overload training had a more significant effect on TT performance than conventional tapering (P < 0.05). A tapering strategy that reduced training volume by 41-60%, maintained training intensity and frequency, lasted ≤7 days, 8-14 days, or 15-21 days, used a progressive or step taper could significantly improve TT performance (P < 0.05).
The tapering applied in conjunction with pre-taper overload training seems to be more conducive to maximize performance gains. Current evidence suggests that a ≤21-day taper, in which training volume is progressively reduced by 41-60% without changing training intensity or frequency, is an effective tapering strategy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Conspectus Building rechargeable batteries for subzero temperature application is highly demanding for various specific applications including electric vehicles, grid energy storage, ...defense/space/subsea explorations, and so forth. Commercialized nonaqueous lithium ion batteries generally adapt to a temperature above −20 °C, which cannot well meet the requirements under colder conditions. Certain improvements have been achieved with nascent materials and electrolyte systems but have mainly been restrained to discharge and within a small rate at temperatures above −40 °C. Moreover, the recharging process of batteries based on the graphite anode still faces huge challenges from the simultaneous Li+ intercalation and potential Li stripping at subzero temperatures. Revealing the temperature-dependent evolution of physicochemical and electrochemical properties will greatly benefit our understanding of the limiting factors at low temperature, which is of significant importance. Herein, we dissect the ion movements in the liquid electrolyte and solid electrode as well as their interphase to analyze the temperature effect on Li+-diffusion behavior during charging/discharging processes. An electrolyte is the vital factor, and its ionic conductivity guarantees the smooth operation of the battery. However, it is the sluggish diffusion in the solid, especially the charge transfer at the solid electrolyte/electrode interfaces (SEI), that greatly limits the kinetics at low temperature. Many strategies have been put forward to tame electrolytes for low-temperature application. From a macroscopic point of view, multiple solvents are mixed to adjust the liquid temperature range and viscosity. With respect to the microscopic nature, research is focusing on the solvation structure by formulating the ratio of Li+ ions to solvent molecules. The binding energy of the Li+–solvent complex is crucial for the desolvation process at low temperature, which is manipulated with fluorinated solvents or other weakly solvating electrolytes. On the basis of an optimized electrolyte, electrodes and their reaction mechanism need to be coupled carefully because different materials show totally different responses to temperature change. To avoid the sluggish desolvation process or slow diffusion in the bulk intercalation compounds, several kinds of materials are summarized for low temperature use. The intercalation pseudocapacitive behavior can compensate for the kinetics to some extent, and a metal anode is a good candidate for replacing a graphite anode to build high-energy-density batteries at subzero temperature. It is also a wise choice to develop nascent battery chemistry based on the co-intercalation of solvent molecules into electrodes. Furthermore, the interfacial resistance contributes a lot at low temperature, which need be modified to accelerate the Li+ diffusion across the film. This will be linked to the electrolyte, exactly speaking, the solvation structure, to regulate the organic and inorganic components as well as the structure. Although it is difficult to investigate SEI on a graphite anode owing to its poor performance at low temperature, great efforts on Li metal anodes have offered some valuable information as reference. It is worth mentioning that the improvement in low-temperature performance calls for not only a change in the single composition but also the synergetic effect of each part in the whole battery. The elementary studies covered in this account could be taken as insight into some key strategies that help advance the low-temperature battery chemistry.
N‐arylcarbazole structures are important because of their prevalence in natural products and functional OLED materials. C−H amination of arenes has been widely recognized as the most efficient ...approach to access these structures. Conventional strategies involving transition‐metal catalysts suffer from confined substrate generality and the requirement of exogenous oxidants. Organocatalytic enantioselective C–N chiral axis construction remains elusive. Presented here is the first organocatalytic strategy for the synthesis of novel axially chiral N‐arylcarbazole frameworks by the assembly of azonaphthalenes and carbazoles. This reaction accommodates broad substrate scope and gives atropisomeric N‐arylcarbazoles in good yields with excellent enantiocontrol. This approach not only offers an alternative to metal‐catalyzed C–N cross‐coupling, but also brings about opportunities for the exploitation of structurally diverse N‐aryl atropisomers and OLED materials.
In the frame: Presented here is the first organocatalytic strategy for the synthesis of novel axially chiral N‐arylcarbazole frameworks by the assembly of azonaphthalenes and carbazoles. This reaction accommodates broad substrate scope and gives atropisomeric N‐arylcarbazoles in good yields with excellent enantiocontrol. This approach offers opportunities for the exploitation of structurally diverse N‐aryl atropisomers and OLED materials. CPA=chiral phosphoric acid.
Hydrogen has been hailed as a clean and sustainable alternative to finite fossil fuels in many energy systems. Water splitting is an important method for hydrogen production in high purity and large ...quantities. To accelerate the hydrogen evolution reaction (HER) rate, it is highly necessary to develop high efficiency catalysts and to select a proper electrolyte. Herein, the performances of non‐noble metal‐based carbon composites under various pH values (acid, alkaline and neutral media) for HER in terms of catalyst synthesis, structure and molecular design are systematically discussed. A detailed analysis of the structure‐activity‐pH correlations in the HER process gives an insight on the origin of the pH‐dependence for HER, and provide guidance for future HER mechanism studies on non‐noble metal‐based carbon composites. Furthermore, this Review gives a fresh impetus to rational design of high‐performance noble‐metal‐free composites catalysts and guide researchers to employ the established electrocatalysts in proper water electrolysis technologies.
Non‐noble‐metal‐based carbon composites for electrochemical hydrogen production are summarized and the relationships between electrocatalyst structure–activity–pH are systematically discussed.
With increased availability and decreased cost, ethanol is potentially a promising platform molecule for the production of a variety of value-added chemicals. In this review, we provide a detailed ...summary of recent advances in catalytic conversion of ethanol to a wide range of chemicals and fuels. We particularly focus on catalyst advances and fundamental understanding of reaction mechanisms involved in ethanol steam reforming (ESR) to produce hydrogen, ethanol conversion to hydrocarbons ranging from light olefins to longer chain alkenes/alkanes and aromatics, and ethanol conversion to other oxygenates including 1-butanol, acetaldehyde, acetone, diethyl ether, and ethyl acetate.
Evolutionary feature selection (FS) methods face the challenge of "curse of dimensionality" when dealing with high-dimensional data. Focusing on this challenge, this article studies a variable-size ...cooperative coevolutionary particle swarm optimization algorithm (VS-CCPSO) for FS. The proposed algorithm employs the idea of "divide and conquer" in cooperative coevolutionary approach, but several new developed problem-guided operators/strategies make it more suitable for FS problems. First, a space division strategy based on the feature importance is presented, which can classify relevant features into the same subspace with a low computational cost. Following that, an adaptive adjustment mechanism of subswarm size is developed to maintain an appropriate size for each subswarm, with the purpose of saving computational cost on evaluating particles. Moreover, a particle deletion strategy based on fitness-guided binary clustering, and a particle generation strategy based on feature importance and crossover both are designed to ensure the quality of particles in the subswarms. We apply VS-CCPSO to 12 typical datasets and compare it with six state-of-the-art methods. The experimental results show that VS-CCPSO has the capability of obtaining good feature subsets, suggesting its competitiveness for tackling FS problems with high dimensionality.
An organocatalytic atroposelective strategy for accessing enantioenriched axially chiral IAN analogues was developed for the first time. A class of novel atropisomeric C2‐arylquinoline skeletons were ...synthesized with high enantiocontrol via chiral phosphoric‐acid‐catalyzed heteroannulation of in situ generated vinylidene ortho‐quinone methide (VQM) intermediates with ortho‐aminophenones. The strategy tolerated a broad substrate scope, providing a facile organocatalytic approach to IAN analogues in good yields and excellent enantioselectivities under mild reaction conditions. Moreover, the synthetic utility of this methodology was illustrated through further transformations into IAN‐type ligand and axially chiral thiourea.
An organocatalytic strategy for accessing enantioenriched axially chiral IAN analogues has been developed. A class of novel atropisomeric C2‐arylquinoline skeletons were synthesized with high enantiocontrol via chiral phosphoric acid catalyzed heteroannulation of alkynes. The synthetic utility was shown by further transformations into IAN‐type ligand and axially chiral thiourea.
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