Durene is a valuable aromatic hydrocarbon used in making polyimide and aviation kerosene additives, which traditionally rely on unsustainable petroleum sources, leading to high costs and ...environmental concerns. Herein, we introduce an alternative method for synthesizing durene with high selectivity through trimethylbenzene methylation coupled with CO2 hydrogenation. Durene selectivity of 83.2% in tetramethylbenzene (TetraMB) and TetraMB selectivity of 69.1% in aromatics were achieved with a 1,2,4-trimethylbenzene conversion of 33.2%. Remarkably, the durene selectivity in TetraMB remained high at 81.4%, even when fed with a mixed trimethylbenzene. The designed composite catalyst 5%CuZnZrO x –HZSM-5 remained active for over 1100 h without significant loss in performance. Further investigations revealed that the role of Cu in the ZnZrO x composite was to provide more active intermediates from the CO2 hydrogenation, thereby enhancing the methylation of aromatics. Detailed studies of the catalyst structure and reaction kinetics indicated that Cu0 is essential for generating active *H species, facilitating CO2 hydrogenation to methoxy, a key intermediate for the methylation of trimethylbenzene.
We report the design, synthesis and properties of spiroindane based compound
1, a potent, selective, orally bioavailable, non-peptide melanocortin subtype-4 receptor agonist. Compound
1 shows ...excellent erectogenic activity in the rodent models.
We report the design, synthesis and properties of spiroindane based compound
1, a potent, selective, orally bioavailable, non-peptide melanocortin subtype-4 receptor agonist. Compound
1 shows excellent erectogenic activity in the rodent models.
We report a series of potent and selective MC4R agonists based on spiroindane amide privileged structures for potential treatments of obesity. Among the synthetic methods used, Method C allows rapid ...synthesis of the analogs. The series of compounds can afford high potency on MC4R as well as good rodent pharmacokinetic profiles. Compound 1r (MK-0489) demonstrates MC4R mediated reduction of food intake and body weight in mouse models. Compound 1r is efficacious in 14-day diet-induced obese (DIO) rat models.
We report a series of potent and selective MC4R agonists based on spiroindane amide privileged structures for potential treatments of obesity. Among the synthetic methods used, Method C allows rapid synthesis of the analogs. The series of compounds can afford high potency on MC4R as well as good rodent pharmacokinetic profiles. Compound 1r (MK-0489) demonstrates MC4R mediated reduction of food intake and body weight in mouse models. Compound 1r is efficacious in 14-day diet-induced obese (DIO) rat models.
Aminotransferases are widely employed as biocatalysts to produce chiral amines and biologically active pharmaceuticals via asymmetric synthesis. In this study, transaminase genes in the Bacillus ...pumilus W3 genome were analysed, and gene ota3 encoding a putative (R)-selective transaminase was identified. The sequence of ota3 shares highest sequence identity (24.7%) with the first (R)-selective aminotransferase from Arthrobacter sp. KNK 168. Amino acid sequence and conserved domains analyses indicated that ω-BPAT encoded by ota3 belonged to the pyridoxal 5′-phosphate-dependent class IV (PLPDE_IV) superfamily. Both native and codon-optimised ω-BPAT genes were recombinantly expressed, and the purified proteins had a molecular mass of ~33.4 kDa. Furthermore, enantioselectivity tests with (S)- and (R)-α-phenethylamine revealed its (R)-selectivity. The optimal conditions for catalytic reaction were 45 °C and pH 7.0, and ω-BPAT retained stability at 20 °C and pH 7.0. Thus, ω-BPAT is a novel (R)-selective aminotransferase with great potential as a universal biocatalyst.
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•The possible genes of transaminase from Bacillus pumilus were first reported.•The transaminase genes were first classified through bioinformatics analysis.•The conserved domain of enzyme ω-BPAT was compared with the typical ω-transaminase.•Codon-optimization of gene ota 3 was performed and its expression was enhanced.
Cu-based catalysts have shown promising prospects in the CO2 hydrogenation reaction but suffer from a significant sintering problem, especially under high temperatures and a reducing atmosphere. ...Herein, we propose a lattice confinement strategy to fabricate a highly dispersed and thermally stable Cu-TiO2 catalyst through a facile ion exchange and calcination reconstruction method. The intrinsic CH3OH formation rate for the optimal Cu-TiO2-600 catalyst reached 55.5 mmol gCu –1 h–1 at 240 °C and 3 MPa. The structural analysis demonstrated that the catalyst maintained an excellent Cu dispersion even at 400 °C and H2 conditions, which exhibited an outstanding sintering resistance property and achieved high activity and thermal stability for CO2 hydrogenation. This work could be potentially extended to construct other lattice-confined catalysts in a heterogeneous catalytic reaction.
Aminotransferases are widely employed as biocatalysts for the asymmetric synthesis of biologically active pharmaceuticals. Transaminase BpTA from Bacillus pumilus W3 can accept a broad spectrum of ...sterically demanding substrates, but it does not process the key five-membered ring intermediate of sitafloxacin. In the present study, we rationally constructed numerous single-point mutants and six multi-point mutants by combining the structural characteristics of transaminase and its substrates. Biochemical characteristics of wild-type and mutant enzymes were initially analyzed, and mutants I215M, I215F, and Y32L displayed increased catalytic efficiency, K155A, I215V and T252A completely lost enzyme activity. Residues K155 and T252 had a particularly strong influence on catalytic activity. Four multi-point mutants (L212M/I215M, Y32L/S190A/L212M/I215M, Y32L/Y159F/T252A and Y32W/Y159F/I215M/T252A) possess potential for industrial production of the key five-membered ring intermediate of sitafloxacin. Furthermore, mutants Y32L/Y159F/T252A and Y32W/Y159F/I215M/T252A can catalyze conversion of (R)-α-phenethylamine, albeit at an extremely low rate (<8%). In summary, mutants L212M/I215M and Y32L/S190A/L212M/I215M are more suitable for industrial production of the antibiotic, sitafloxacin, via an enzymatic approach.
The mutants that could accept the sitafloxacin intermediate were rationally designed: Display omitted
•The catalytic site K155 of the transaminase BpAT was verified.•The mutants that accept the sitafloxacin intermediate were rationally designed.•Residue sites that may be responsible for identifying enantiomers were revealed.•Molecular dynamics experiments were performed on specific mutants.
Ni-based bimetallic catalysts have been widely used in the water-gas shift (WGS) reaction, but the synergistic effect and reaction mechanism over bimetallic catalysts are rather limited. In this ...work, the WGS reaction mechanism and the main side-reaction (coke formation) over the NiM catalysts (NiFe(111), NiCo(111), NiCu(111) and NiZn(111) surfaces) are investigated
via
the density functional theory (DFT) approach. The results show that a second metal element (Fe, Co, Cu and Zn) leads to the dispersion of active Ni atoms on the NiM surfaces and M sites can also act as active sites, which increase the energy barriers for coke formation. Binary linear regression of site size and electron factors to adsorption energy of H
2
O and CO reveals that the ligand effect plays a more important role in determining adsorption strength than the strain effect on NiFe(111) and NiCo(111), while for NiCu(111) and NiZn(111) surfaces, the adsorption energies are strongly affected by strain rather than ligand effects. The WGS mechanism is further calculated over NiCo (111) and NiCu(111), which present both less carbon deposition and better H
2
O dissociation ability than the others. It is illustrated that on NiCo(111), the redox path is the most favorable, and the CO association with O is the rate determining step while on NiCu(111), the dominant pathway is the carboxyl path with the association of CO and OH to form COOH as the rate determining step. In addition, experimental studies verify that the NiCo and NiCu samples exhibit the optimum catalytic activity and resistance against carbon deposition, which accords well with the theoretical prediction. This study provides guidance for the rational design of Ni-based bimetallic catalysts for the WGS reaction based on the chemical nature and electronic environment of the doped metal.
The water gas shift reaction (WGS) process on the NiM(111) bimetallic surfaces (M = Fe, Co, Cu, Zn) are studied by density functional theory method and experimental studies. The NiCo and NiCu exhibit the optimum catalytic activity and CO
2
selectivity.
The alkylation reaction of aromatic compounds gains considerable attention because of its wide application in bulk and fine chemical production. Developing green alkylation reagents and efficient ...alkylation routes is the goal pursued by researchers. As a recyclable carbon carrier and hydrogen storage medium, formic acid is expected to be a widely used alkylation reagent because of its high reactivity and various functional groups. The decomposition route of formic acid dehydration or dehydrogenation and the adsorption mechanism of formate or carboxylate are expected to match the alkylation reactions of a wide range of substrates, thereby placing high demands on active site design. Accordingly, this review presents the current state of the art and outlook regarding the heterogeneously catalytic alkylation reaction of aromatics using sustainable formic acid. The future research directions for developing new heterogeneous catalysts with transformational technologies, including machine-learning-assisted catalyst optimization, are prospected.
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Formic acid is potentially a recyclable CO2 carrier and H2 storage medium, and its functional groups can potentially alkylate various substrates. Zuo et al. summarize the use of formic acid in the alkylation of aromatics and highlight opportunities to expand the applicability of formic acid as an efficient alkylation reagent.
