Nitro-, Cyano-, and Methylfuroxans,and Their Bis-Derivatives: From Green Primary to Melt-Cast Explosives

In the present work, we studied in detail the thermochemistry, thermal stability, mechanical sensitivity, and detonation performance for 20 nitro-, cyano-, and methyl derivatives of 1,2,5-oxadiazole-2-oxide (furoxan), along with their bis-derivatives. For all species studied, we also determined the reliable values of the gas-phase formation enthalpies using highly accurate multilevel procedures W2-F12 and/or W1-F12 in conjunction with the atomization energy approach and isodesmic reactions with the domain-based local pair natural orbital (DLPNO) modifications of the coupled-cluster techniques. Apart from this, we proposed reliable benchmark values of the formation enthalpies of furoxan and a number of its (azo)bis-derivatives. Additionally, we reported the previously unknown crystal structure of 3-cyano-4-nitrofuroxan. Among the monocyclic compounds, 3-nitro-4-cyclopropyl and dicyano derivatives of furoxan outperformed trinitrotoluene, a benchmark melt-cast explosive, exhibited decent thermal stability (decomposition temperature >200 °C) and insensitivity to mechanical stimuli while having notable volatility and low melting points. In turn, 4,4′-azobis-dicarbamoyl furoxan is proposed as a substitute of pentaerythritol tetranitrate, a benchmark brisant high explosive. Finally, the application prospects of 3,3′-azobis-dinitro furoxan, one of the most powerful energetic materials synthesized up to date, are limited due to the tremendously high mechanical sensitivity of this compound. Overall, the investigated derivatives of furoxan comprise multipurpose green energetic materials, including primary, secondary, melt-cast, low-sensitive explosives, and an energetic liquid.     

The Effect of Enantiomer Elution Order on the Determination of Minor Enantiomeric Impurity in Ketoprofen and Enantiomeric Purity Evaluation of Commercially Available Dexketoprofen Formulations

In a recent study, opposite enantiomer elution order was observed for ketoprofen enantiomers on two amylose-phenylcarbamate-based chiral columns with the same chemical composition of the chiral selector but in one case with coated while in the other with an immobilized chiral selector. In the present study, the influence of this uncommon effect on method validation parameters for the determination of minor enantiomeric impurity in dexketoprofen was studied. The validated methods with two alternative elution orders for enantiomers were applied for the evaluation of enantiomeric impurity in six marketed dexketoprofen formulations from various vendors. In most of these formulations except one the content of enantiomeric impurity exceeded 0.1% (w/w).     

Disentangling Reaction Processes of Zeolites within Single‐Oriented Channels

Establishing structure–reactivity relationships for specific channel orientations of zeolites is vital to developing new, superior materials for various applications, including oil and gas conversion processes. Herein, a well‐defined model system was developed to build structure–reactivity relationships for specific zeolite‐channel orientations during various catalytic reaction processes, for example, the methanol‐ and ethanol‐to‐hydrocarbons (MTH and ETH) process as well as oligomerization reactions. The entrapped and effluent hydrocarbons from single‐oriented zeolite ZSM‐5 channels during the MTH process were monitored by using operando UV/Vis diffuse reflectance spectroscopy (DRS) and on‐line mass spectrometry (MS), respectively. The results reveal that the straight channels favor the formation of internal coke, promoting the aromatic cycle. Furthermore, the sinusoidal channels produce aromatics, (e.g., toluene) that further grow into larger polyaromatics (e.g., graphitic coke) leading to deactivation of the zeolites. This underscores the importance of careful engineering of materials to suppress coke formation and tune product distribution by rational control of the location of zeolite acid sites and crystallographic orientations.     

Fabrication of Heterostructured Fe2TiO5–TiO2 Nanocages with Enhanced Photoelectrochemical Performance for Solar Energy Conversion

Photocatalysts with well‐designed compositions and structures are desirable for achieving highly efficient solar‐to‐chemical energy conversion. Heterostructured semiconductor photocatalysts with advanced hollow structures possess beneficial features for promoting the activity towards photocatalytic reactions. Here we develop a facile synthetic strategy for the fabrication of Fe₂TiO₅–TiO₂ nanocages (NCs) as anode materials in photoelectrochemical (PEC) water splitting cells. A hydrothermal reaction is performed to transform MIL‐125(Ti) nanodisks (NDs) to Ti–Fe–O NCs, which are further converted to Fe₂TiO₅–TiO₂ NCs through a post annealing process. Owing to the compositional and structural advantages, the heterostructured Fe₂TiO₅–TiO₂ NCs show enhanced performance for PEC water oxidation compared with TiO₂ NDs, Fe₂TiO₅ nanoparticles (NPs) and Fe₂TiO₅–TiO₂ NPs.     

Tiara[5]arenes: Synthesis,Solid‐State Conformational Studies,Host–Guest Properties,and Application as Nonporous Adaptive Crystals

Tiara[5]arenes (T[5]s), a new class of five‐fold symmetric oligophenolic macrocycles that are not accessible from the addition of formaldehyde to phenol, were synthesized for the first time. These pillar[5]arene‐derived structures display both unique conformational freedom, differing from that of pillararenes, with a rich blend of solid‐state conformations and excellent host–guest interactions in solution. Finally we show how this novel macrocyclic scaffold can be functionalized in a variety of ways and used as functional crystalline materials to distinguish uniquely between benzene and cyclohexane.     

Bifunctionalized allenes. Part XXIV. Competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-alka-3,4-dienoates leading to 2,5-dihydro-1, 2-oxaphospholes and 5,6-dihydro-2H-pyranes

Abstract

We report herein a study on the competitive electrophilic cyclization of 5-(dimethoxyphosphoryl)-alka-3,4-dienoates involving 5-endo-trig and 6-endo-trig mode cyclizations. Reaction with electrophiles produces mixtures of the 2-(2-oxo-2,5-dihydro-1,2-oxaphosphol-5-yl)-alkanoates and (6-oxo-5,6-dihydro-2H-pyran-2-yl)-phosphonates by competitive electrophilic cyclization due to the participation of the neighboring phosphonate and carboxylate groups.     

Analytical method development and validation of anticancer agent, 5-fluorouracil,and its metabolites in biological matrices: An updated review

Abstract

5-fluorouracil (5-FU) refers to a fluorinated pyrimidine analogue that has been widely used as an anticancer agent for colon, head, and neck cancers. Detection of 5-FU and its metabolites; 5-fluorouridine and 5-fluoro-2-deoxyuridine in biological samples allows optimization of pharmacotherapy and encourages fundamental investigations of this medication. The development of accurate and reliable sample preparation, as well as analytical methods, is critical to isolate targeted analytes from complex matrices, apart from increasing detection sensitivity of analytes. With that, this paper presents a review of prior studies pertaining to chromatographic and electrophoretic methods that focused on the analysis of 5-FU and its metabolites in biological matrices such as plasma and urine. This paper concentrates on HPLC, GC and CE systems, which are the most commonly used strategies for analytical separation of 5-FU and its metabolites from samples. Detection of these antineoplastic agents at trace level demands highly sensitive and selective analytical methodologies. Application of these analytical techniques to biological matrices is reviewed with a focus on method development strategies, including types of mobile phases and background electrolytes employed in LC and CE systems.     

Coptis chinensis Franch Directly Inhibits Proteolytic Activation of Kallikrein 5 and Cathelicidin Associated with Rosacea in Epidermal Keratinocytes

Rosacea is a common and chronic inflammatory skin disease that is characterized by dysfunction of the immune and vascular system. The excessive production and activation of kallikerin 5 (KLK5) and cathelicidin have been implicated in the pathogenesis of rosacea. Coptis chinensis Franch (CC) has been used as a medicinal herb in traditional oriental medicine. However, little is known about the efficacy and mechanism of action of CC in rosacea. In this study, we evaluate the effect of CC and its molecular mechanism on rosacea in human epidermal keratinocytes. CC has the capacity to downregulate the expression of KLK5 and cathelicidin, and also inhibits KLK5 protease activity, which leads to reduced processing of inactive cathelicidin into active LL-37. It was determined that CC ameliorates the expression of pro-inflammatory cytokines through the inhibition of LL-37 processing. In addition, it was confirmed that chitin, an exoskeleton of Demodex mites, mediates an immune response through TLR2 activation, and CC inhibits TLR2 expression and downstream signal transduction. Furthermore, CC was shown to inhibit the proliferation of human microvascular endothelial cells induced by LL-37, the cause of erythematous rosacea. These results demonstrate that CC improved rosacea by regulating the immune response and angiogenesis, and revealed its mechanism of action, indicating that CC may be a useful therapeutic agent for rosacea.     

A High Performing Zn‐Ion Battery Cathode Enabled by In Situ Transformation of V2O5 Atomic Layers

Developing high capacity and stable cathodes is a key to successful commercialization of aqueous Zn‐ion batteries (ZIBs). Pure layered V₂O₅ has a high theoretical capacity (585 mAh g^?1), but it suffers severe capacity decay. Pre‐inserting cations into V₂O₅ can substantially stabilize the performance, but at an expense of lowered capacity. Here we show that an atomic layer deposition derived V₂O₅ can be an excellent ZIB cathode with high capacity and exceptional cycle stability at once. We report a rapid in situ on‐site transformation of V₂O₅ atomic layers into Zn₃V₂O₇(OH)₂?2 H₂O (ZVO) nanoflake clusters, also a known Zn‐ion and proton intercalatable material. High concentration of reactive sites, strong bonding to the conductive substrate, nanosized thickness and binder‐free composition facilitate ionic transport and promote the best utilization of the active material. We also provide new insights into the V₂O₅‐dissolution mechanisms for different Zn‐salt aqueous electrolytes and their implications to the cycle stability.     

Insights into high mobility group A (HMGA) proteins from Poaceae family: An in silico approach for studying homologs

High mobility group (HMG) proteins are the major architectural proteins. Among HMG proteins, High Mobility Group A (HMGA) is characterized by AT-hook (ATH) motifs, which have an affinity for AT-rich DNA. In this study, we characterized the plant HMGAs from the Poaceae family using in silico methods. The protein sequences for rice HMGAs were retrieved and the corresponding orthologs from grasses were extracted. The phylogenetic analysis identified three major evolutionary clades of grass HMGAs and their ATH motif analysis revealed that HMGAs from clade 1 and 2, except for clade 2 HMGAs, are devoid of high-affinity DNA-binding domain. The clade 2 HMGAs also displayed a highly conserved length of all the spacers and the length of the C-terminal tail following the last ATH. Moreover, the C-terminal tail in clade 2 HMGAs is smaller than HMGAs from any other clade. Unlike clade 2, other clades of Poaceae HMGAs displayed high variability in the length of spacers. Despite several differences among HMGAs of different clades in Poaceae, the H1/H5 domain was found to be highly conserved. This study has revealed the detailed analyses of Poaceae HMGAs and it will be useful for further investigation aiming at the determination of precise biological functions and molecular mechanisms of grass HMGAs.