Search Results (88)

Purification of isobutane remains a fundamental step in the production of a cleaner alkylated gasoline, and the distillation operation employed for this separation is notoriously energy-intensive and a significant contributor to environmental impacts. To address these challenges, this work proposes vapor recompression (VR) as an intensified alternative process to fully electrify the conventional column–reactor configuration used in n-butane isomerization and separation. An external VR scheme was designed and globally optimized with the objective of minimizing total annualized cost. The optimized VR configuration showed a clear economic advantage, achieving an approximate 13.83% reduction in costs over a 10-year horizon with a break-even time of 7.13 years. Additionally, overall energy demand was reduced by 74%, and operational safety was enhanced, as the boiler is required only during plant start-up and shutdown. To account for economic uncertainty, a sensitivity analysis was conducted to evaluate the effects of fluctuations in electricity and steam prices. Environmental performance was further assessed through CO₂ emissions using different national electricity emission factors. While emission reductions depend strongly on grid carbon intensity, regions with low-carbon electricity mixes show significant mitigation potential. Overall, VR emerges as a promising strategy to improve the economic and environmental sustainability of industrial processes. Full article

Co and Mo mono- and bimetallic catalysts supported on CNT-H-ZSM-5 composites were prepared and characterized using various techniques. The catalysts were evaluated for the conversion of sunflower oil (SO) into sustainable aviation fuel (SAF) hydrocarbons in the C₈–C₁₆ range. The effects of reduction temperature and metal loading were the main parameters investigated in this study. The catalyst reduced at 600 °C promoted the formation of Mo₂C species, resulting in high SO conversion (84%), complete deoxygenation, and enhanced isomerization within the C₈–C₁₆ fraction. Optimal metal loadings (2.5 wt% Co and 8 wt% Mo) and the bimetallic configuration led to superior performance compared with monometallic catalysts and physical mixtures, clearly highlighting a synergistic effect between Co and Mo species. In contrast, when waste cooking oil was used as feedstock, lower conversion and reduced selectivity toward SAF-range hydrocarbons were observed, which were attributed to the higher complexity and impurity content of this residue feedstock. Full article

Polyamide thin-film composite reverse osmosis membranes were fabricated through interfacial polymerization (IP), wherein trimesoyl chloride (TMC) and isomeric diamine monomers including o-phenylenediamine (OPD), m-phenylenediamine (MPD), p-phenylenediamine (PPD), and methyl-substituted monomers such as 2,3-diaminotoluene (MOPD), 2,4-diaminotoluene (MMPD), 2,5-diaminotoluene (MPPD), and 2,6-diaminotoluene (2,6-MMPD) were employed. The membranes with high permeation flux and rejection ratio were eventually applied in the desalination of brackish water. The regional effects of the amino and methyl substituent on the desalination performance of the RO membranes in terms of permeation flux and rejection ratio were investigated extensively. A molecular dynamics simulation based on the configuration of monomers was performed to theoretically explore the effects of amino and methyl groups of the monomer on the packing density of the aromatic molecular structure and, consequently, on the desalination performance of the corresponding RO membranes. The RO membranes with integrated monomers exhibited two times higher permeation flux than that of a pristine RO membrane while remaining the high rejection ratio. Moreover, a long-term desalination performance of the RO membrane was also demonstrated, where two times higher permeation flux than that of conventional and commercial RO membranes was achieved, while the rejection ratio was maintained at 97.6% which was comparable with that of the commercial RO membranes. Full article

This review summarizes current knowledge on naturally occurring pristimerin-pristimerin triterpenoid dimers, a rare and structurally diverse class of secondary metabolites reported mainly from Celastraceae species. Known dimers are compiled with emphasis on botanical sources and key architectural features, including the variety of interunit linkages, regio- and stereochemical diversity, and distinct isomeric forms (including atropisomerism). Major advances in structure elucidation and structural revisions are discussed, highlighting the role of modern spectroscopic tools—particularly 2D NMR methods and chiroptical techniques—in resolving connectivity and absolute configuration, and in correcting several earlier assignments. Proposed biosynthetic scenarios are outlined, focusing on the reactivity of the quinone-methide motif and its interconversion with 2,3-diketone forms, as well as (hetero) Diels-Alder-type processes; selected biomimetic studies are summarized as supportive evidence for these pathways. A critical overview of available biological data indicates that many pristimerin dimers display limited activity in common antimicrobial and cytotoxicity assays when compared with monomeric congeners, which may point to alternative ecological roles or storage/transport functions in planta. Finally, key knowledge gaps and future directions are identified, including improved isolation coverage, rigorous synthetic/biomimetic work, and broader pharmacological screening beyond standard panels. Full article

Eupalinolide A (EA, Z-configuration) and Eupalinolide B (EB, E-configuration) are cis-trans isomeric sesquiterpenoid monomers isolated from Eupatorium lindleyanum DC. (Asteraceae). Although these compounds display anti-inflammatory and anti-tumor activities, their metabolite profiles and possible hepatotoxicity remain largely unknown. This study aimed to investigate the metabolic profiles of EA and EB in liver microsomes and clarify whether they undergo metabolic activation or detoxification. EA and EB were metabolically profiled in human liver microsomes (HLMs) via UPLC-Q-TOF-MS. A HepG2-HLM co-culture system was used to compare the hepatocyte toxicity of parent compounds and their hydrolysis, oxidation, and hydrolysis–oxidation metabolites, thus evaluating their metabolic detoxification pathways. Sixteen metabolites of EA and 19 of EB were identified, with hydrolysis being the predominant metabolic pathway for both isomers. Both compounds showed low hepatocyte toxicity and underwent metabolic detoxification mainly via hydrolytic and oxidative pathways. Notably, hydrolysis metabolites had significantly lower toxicity than oxidative products in HepG2 cells. These results suggest that EA and EB could present a relatively low risk of in vivo hepatotoxicity, which provides useful information for understanding the metabolic behavior and safety profile of these bioactive sesquiterpenoids. Full article

The development of Sustainable Aviation Fuel (SAF) is a crucial pathway to achieving carbon neutrality goals in the aviation industry. In the preparation process of SAF, the performance of catalysts is a core factor determining reaction efficiency, product distribution, and selectivity. Among these, zeolite molecular sieves play an irreplaceable key role in catalytic systems. This paper, through an in-depth survey and systematic analysis of over 70 core literature pieces in related fields, primarily elucidates the structural regulation mechanisms of zeolite catalysts in key reaction steps such as deoxygenation, hydrocracking, and isomerization. Research indicates that differences in pore size, pore channel configuration, and acidity distribution of zeolite molecular sieves with different topological structures (one-dimensional channels such as SAPO-11 and ZSM-22; three-dimensional intersecting channel micropores such as ZSM-5; three-dimensional twelve-membered ring micropores such as Y-type and Beta zeolites) directly affect the selectivity of catalytic reactions and product quality. Full article

A novel unsymmetrical azine, 6-((2-oxoindolin-3-ylidene)hydrazineylidene)indolo[2,1-b]quinazolin-12(6H)-one, was synthesized through a condensation reaction between tryptanthrin-6-hydrazone and isatin in chloroform under reflux conditions. Structural characterization revealed the compound exists as a mixture of geometric isomers with one predominant form. Density functional theory (DFT) calculations identified the E,E configuration as the most stable isomer. The isomerization barriers for both C=N bonds were calculated at approximately 18.5 kcal/mol via nitrogen inversion. Given the established biological activities of tryptanthrin and isatin derivatives, this hybrid azine represents a promising lead compound for developing bifunctional drug candidates. Full article

Membrane-targeted photoswitches are emerging as innovative tools to modulate cardiac excitability with high spatiotemporal precision. Ziapin2, a membrane-integrating azobenzene derivative, undergoes light-driven trans–cis isomerization that alters membrane capacitance (C_m). In its trans configuration, Ziapin2 increases C_m, while illumination relaxes the membrane and restores C_m toward baseline. Here, we investigated whether Ziapin2 can modulate conduction velocity (CV) in strands of neonatal or fetal murine cardiomyocytes cultured on microelectrode arrays. In the dark, trans-Ziapin2 significantly reduced CV, consistent with increased capacitive load slowing action potential propagation. Unexpectedly, photostimulation further decreased CV, likely reflecting the documented transient, capacitive-driven perturbations of the membrane potential, occurring without alterations in cellular conductances. These findings suggest that non-genetic light modulation of membrane capacitance can influence cardiac conduction and establish Ziapin2 as a novel optical tool to modulate cardiac impulse propagation. Full article

Neutral and protonated histamine tautomers, mono-substituted with twelve functional groups, were studied theoretically as isolated molecules and complexes with the H₁ receptor. Geometry and energy of tautomers were optimized using the DFT method with the B3LYP functional and the aug-cc-pVTZ basis set. The approach was based on the charge of the substituent active region (cSAR) parameters and the Harmonic Oscillator Model of Aromaticity (HOMA) indices. The cSAR parameters characterized the electron density better than the conventional Hammett’s constants σ. In general, the cSAR parameters correlate with other characteristics of the charge distribution, particularly those for substituents at the carbon atom in the ring adjacent to the side chain. Substituents at this atom affected the aromaticity less strongly than those located between two nitrogen atoms, which confirmed recent reports. Our results suggest that the 3H tautomer isomerizes into the 1H one after binding to the H₁ receptor. Moreover, the electron structure of the molecule hydrogen-bonded to the receptor may significantly depend on the electron donor-acceptor properties of the substituent. The strong electron-accepting substituents, e.g., NO₂, favor the imidazole configuration of the ring in the bonded molecule, while the strong electron-donating ones, e.g., NH₂, promote the imidazolium one. Full article

Inspired by naturally occurring bis-isochromans such as penicisteckins, we envisaged the first synthesis of biaryl-type bis-1-arylisochromans containing a stereogenic ortho-trisubstituted biaryl axis. We achieved the stereoselective synthesis of 5,5′-linked heterodimeric bis-isochromans containing both central and axial chirality elements by performing diastereoselective Suzuki–Miyaura biaryl coupling reactions on two optically active 1-arylpropan-2-ol derivatives, followed by two oxa-Pictet–Spengler cyclizations with aryl aldehydes or methoxymethyl chloride. We studied the diastereoselectivity of the cyclization step, separated the stereoisomeric products with chiral preparative HPLC and determined the absolute configuration through a combination of vibrational circular dichroism (VCD), NMR and single-crystal X-ray diffraction analysis. We demonstrated that different aryl groups could be introduced into the two isochroman subunits, since the dimethoxyaryl subunit reacted faster, enabling the two oxa-Pictet–Spengler cyclizations to be performed separately with different aryl aldehydes. We also explored the acid-catalyzed isomerization and oxidation to axially chiral ortho-quinones in order to produce stereoisomeric and oxidized analogs, respectively. We identified the antibacterial activity of our target bis-isochromans against Bacillus subtilis and Enterococcus faecalis with minimum inhibitory concentrations down to 4.0 and 0.5 μg/mL, respectively, which depend on the stereochemistry and substitution pattern of the bis-isochroman skeleton. Full article

The development of novel platinum-based anticancer agents remains a critical objective in medicinal inorganic chemistry, particularly in light of resistance and toxicity limitations associated with cisplatin. In this study, the synthesis, structural characterization, quantum chemical analysis, and cytotoxic evaluation of four new acetylplatinum(II) complexes (cis-[Pt(COMe)₂(PASO₂)₂], cis-[Pt(COMe)₂(DAPTA)₂], trans-[Pt(COMe)Cl(DAPTA)₂], and trans-[Pt(COMe)Cl(PASO₂)]: 1–4, respectively) bearing cage phosphine ligands PASO₂ (2-thia-1,3,5-triaza-phosphaadamantane 2,2-dioxide) and DAPTA (3,7-diacetyl-1,3,7-triaza-5-phosphabicyclo[3.3.1]nonane) are presented. The coordination geometries and NMR spectral features of the cis/trans isomers were elucidated through multinuclear NMR and DFT calculations at the B3LYP/6-311++G(d,p)/LanL2DZ level, with strong agreement between experimental and theoretical data. Quantum Theory of Atoms in Molecules (QTAIM) analysis was applied to investigate bonding interactions and assess the covalent character of Pt–ligand bonds. Cytotoxicity was evaluated against five human cancer cell lines. The PASO₂-containing complex in cis-configuration, 1, demonstrated superior activity against thyroid (8505C) and head and neck (A253) cancer cells, with potency surpassing that of cisplatin. The DAPTA complex 2 showed enhanced activity toward ovarian (A2780) cancer cells. These findings highlight the influence of ligand structure and isomerism on biological activity, supporting the rational design of phosphine-based Pt(II) anticancer drugs. Full article

Calcipotriol, a synthetic vitamin D₃ analogue widely used in psoriasis treatment, requires a detailed stability assessment due to its topical application and potential exposure to UV radiation. As a drug applied directly to the skin, calcipotriol is particularly susceptible to photodegradation, which may affect its therapeutic efficacy and safety profile. The present study focuses on the analysis of calcipotriol photostability. An advanced UHPLC/MS^E method was employed for the precise determination of calcipotriol and its degradation products. Particular attention was given to the effects of commonly used organic UV filters—approved for use in cosmetic products in both Europe and the USA (benzophenone-3, dioxybenzone, meradimate, sulisobenzone, homosalate, and avobenzone)—on the stability of calcipotriol. Unexpected degradation of calcipotriol was observed in the presence of sulisobenzone. Importantly, this effect was consistently detected in methanolic solution and in the pharmaceutical formulation containing calcipotriol and betamethasone, which is particularly significant from a practical perspective. This finding underscores the necessity of evaluating photostability under real-life conditions, as cosmetic ingredients, when co-applied with topical drugs on the skin, may substantially influence the stability profile of the pharmaceutical active ingredient. The research resulted in the first-time characterization of four degradation products of calcipotriol. The degradation process was found to primarily affect the E-4-cyclopropyl-4-hydroxy-1-methylbut-2-en-1-yl moiety, causing its isomerization to the Z isomer and the formation of diastereomers with either the R or S configuration. Computational analyses using the OSIRIS Property Explorer indicated that none of the five degradation products exhibit a toxicity effect, whereas molecular docking studies suggested possible binding of two of the five degradation products of calcipotriol with the VDR. Full article

N-phenyl-1H-Indole-5-carboxamide (Ind-CA) exhibits previously unknown room-temperature phosphorescence (RTP) when immobilized in poly (vinyl alcohol) film (PVA film). High-fluorescence anisotropy of Ind-CA in PVA suggests that the fluorophores are strongly immobilized in a polymer matrix, while a relatively low (ca. 0.1) quantum yield indicates a strong non-radiative singlet excited state deactivation. With an increased triplet-state population, Ind-CA can be used for various phosphorescence studies. The room-temperature phosphorescence (RTP) capability of Ind-CA indicates that there is an intricate balance between RTP and the structure of the indole-containing luminophore, as an isomeric N-1H-indole-5-ylbenzamide (Ind-BA) does not show any appreciable levels of RTP. Moreover, the phosphorescence lifetime of Ind-CA is about two orders of magnitude longer than many other 5-substituted indoles. These results further highlight the prospects for the potential rational designs of small molecules with desired triplet-state configuration and RTP characteristics. Full article

A stereoselective and scalable strategy for the synthesis of phosphorus-containing bicyclic and tricyclic compounds from 1-phenylphosphin-2-en-4-one 1-oxide is presented. This activated dienophile, available in both racemic and enantiopure forms, undergoes smooth [4+2] cycloadditions with acyclic and cyclic dienes, affording products with excellent yields and controlled stereochemistry. Notably, the cis/trans-fusion of the cycloadducts (phosphadecalones and phosphahexahydrochrysene) can be selectively controlled by fine-tuning the conditions of microwave-assisted cycloaddition reaction. The influence of temperature, time, and steric effects on cis/trans and endo/exo selectivity was examined in detail. The molecular structure, including the absolute configuration, of eight products has been determined by X-ray crystallography. These analyses further established the endo-selective nature of the cycloaddition, favoring the P=O face of the dienophile. Post-cycloaddition transformations of selected P-stereogenic phosphadecalone, such as isomerization, reduction and deoxygenation, demonstrate the synthetic versatility of the resulting products. Full article

As a significant by-product of coal pyrolysis processes, coal tar is rich in polycyclic aromatic hydrocarbons (PAHs), garnering considerable attention for their potential conversion into high-value products through saturation hydrogenation. This paper presents a comprehensive review of recent advancements in two key areas: progress in high-activity saturated hydrogenation of PAHs catalyzed by precious metals and the regulation of cis–trans isomeric configuration of their hydrogenation products. Furthermore, the investigation addresses two critical challenges involved in the field: the susceptibility of precious metal catalysts to sulfur poisoning during the coal tar’s hydrogenation and the difficulty in controlling the stereo-isomerization of hydrogenation products. This review will advance fundamental understanding of PAHs hydrogenation mechanisms and provide critical technical guidance in coal tar utilization, supporting the sustainable development of clean energy technologies and high-value chemical production from coal by-products. Full article