Monthly Archives: September 2023

Synthesis and Electrochemical Investigation of Phosphine Substituted Diiron Phosphadithiolate Complexes

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Synthesis and Electrochemical Investigation of Phosphine Substituted Diiron Phosphadithiolate Complexes

Six novel phosphine substituted [FeFe] hydrogenase models with phosphinate in the bridgehead were synthesized and investigated by FTIR spectroscopy and cyclic voltammetry (CV). These ligand exchange reactions occur at milder conditions compared to literature procedures, resulting in a ligand-specific main product in all cases. Additionally, reflux conditions only influenced the complexes with bidentate ligands.


Abstract

This work reports on ligand exchange reactions between a [FeFe] hydrogenase model containing the higher homologue (PhosDT) and phosphines selected to cover a variety of electronic properties and possible coordination modes. Additionally, the amount of the phosphines and the reaction temperature were varied to study the formation of complexes with multiple phosphines or altered binding modes. Due to steric effects caused by the position of the bridgehead, the phosphines bind preferentially at the more accessible iron centre on the phosphinate averted side. While all ligand exchanges resulted in a ligand-specific main product at room temperature, reflux conditions induced decomposition in case of PhosDT-(κ2-dppe) and PhosDT-(κ2-dppv) and a change in the binding mode for the dppm containing complex. Moreover, we highlight two novel iron complexes obtained as side products of the reactions with dppe and dppv, while in case of dppm an additional model with two bridging phosphine ligands was generated. Finally, the six novel phosphine substituted PhosDT models were electrochemically investigated, revealing a cathodic shift compared to the starting material due to the increased electron density at the iron atoms. Moreover, the models with monodentate ligands exhibit a different CV pattern for the FeIFeI/FeIFe0 process than complexes with bidentate phosphines.

Three‐Dimensional Scaffolds for Light Emission

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Three-Dimensional Scaffolds for Light Emission

Here, we reported novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance.


Abstract

Organic fluorophores with highly efficient luminescence in both solution and solid states have attracted significant attention due to their ability to circumvent the limitations of aggregation-caused quenching and aggregation-induced emission type molecules. However, their development and wide-range applications are hampered by extremely complex synthetic methodologies and limited frameworks with dual-state emission (DSE) structural characteristics. In sharp contrast to the reported luminogens with big and planar π systems or highly conjugated and twisted structures, we discovered novel three-dimensional scaffolds in one molecule to achieve DSE. These molecules allowing for rapid access showed completely different molecular packing manners from those of planar conjugated molecules and exhibited excellent optoelectronic properties with diminished intermolecular π−π stacking interactions due to steric hindrance. Our findings should open new avenues for designing DSE molecules with new frameworks, which will enable more successful development of dual-state emitters for their broad applications in the future.

Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’‐Carbonyldiimidazole Activated Fatty Acids

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Synthesis of Deuterated and Protiated Triacylglycerides by Using 1,1’-Carbonyldiimidazole Activated Fatty Acids

A practical methodology for the synthesis of triacylglycerides utilizing fatty acids activated by 1,1’-carbonyldiimidazole (CDI) was developed to obtain protiated and deuterated medium chain triglyceride (MCT) oils as well as a synthetic plant oil mimic. New insights into the mechanism of the CDI activation were gained using deuterated substrates and via density-functional theory (DFT) calculations.


Abstract

Synthetic model triacylglyceride oils are important compounds for applications in pharmaceutical and food chemistry. Herein, a practical and highly efficient methodology for the synthesis of saturated and unsaturated triacylglycerides utilizing saturated and unsaturated fatty acids activated by 1,1’-carbonyldiimidazole (CDI) has been developed and applied in the synthesis of deuterated medium chain triglyceride (MCT) oil for studies of plant-based and diary food emulsions. The deuterium labelled compounds were used to gain new insight into the mechanism of the reaction, which was confirmed by density-functional theory (DFT) calculations.

Tandem Conversion of Fructose to Bio‐diketones Using a Multifunctional Pd‐POPs‐CF3SO3H Catalyst

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Tandem Conversion of Fructose to Bio-diketones Using a Multifunctional Pd-POPs-CF3SO3H Catalyst

A multifunctional heterogeneous Pd-POPs-CF3SO3H catalyst containing integrated acid and metal sites and anions was synthesized for tandem conversion of fructose to bio-diketones in good yield with an extraordinary TOF.


Abstract

Tandem conversion of biomass to value-added fine chemicals is a significant challenge. For instance, the production of fine chemicals from fructose involves conversion to 5-hydroxymethylfurfural (5-HMF), followed by another reaction and purification. Dual catalyst systems have been used in nearly every study on the tandem conversion of fructose to bio-diketones. Therefore, a sole multifunctional heterogeneous catalyst was developed in this study for the tandem conversion of fructose to bio-diketones, which has not been reported previously. Instrument corrosion and the separation or purification of 5-HMF were avoided using the multifunctional heterogeneous catalyst, which contained integrated active sites of acid, metal, and anions. The multifunctional CF3SO3H-functionalized porous-organic-polymers(POPs)-supported Pd catalyst (Pd-POPs-CF3SO3H) was prepared using a series of modifications. A bio-diketone yield of 51.0 % was achieved using Pd-POPs-CF3SO3H in the tandem conversion of fructose with an excellent TOF of 88.3 h−1 which is much more efficient than catalyst reported in literatures. Pd-POPs-CF3SO3H could be reused at least three times with stable performance. Control experiments and characterization results proved that the high specific surface area, hierarchical pore structure, abundance of CF3SO3 −1 anions, and proximity of Pd moieties and acid sites (“The closer the better” principle) led to the decent performance for bio-diketone.

Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage‐Gated Sodium Channels

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Trifunctional Saxitoxin Conjugates for Covalent Labeling of Voltage-Gated Sodium Channels**

Trifunctional chemical probes derived from the potent shellfish poison, (+)-saxitoxin (STX), irreversibly inhibit wild-type voltage-gated sodium channels (NaVs). Saxitoxin derivatives decorated with a maleimide electrophile and either biotin, a fluorescent dye, or biorthogonal-reactive group were synthesized and evaluated using whole-cell, voltage-clamp electrophysiology.


Abstract

Voltage-gated sodium ion channels (NaVs) are integral membrane protein complexes responsible for electrical signal conduction in excitable cells. Methods that enable selective labeling of NaVs hold potential value for understanding how channel regulation and post-translational modification are influenced during development and in response to diseases and disorders of the nervous system. We have developed chemical reagents patterned after (+)-saxitoxin (STX) – a potent and reversible inhibitor of multiple NaV isoforms – and affixed with a reactive electrophile and either a biotin cofactor, fluorophore, or ‘click’ functional group for labeling wild-type channels. Our studies reveal enigmatic structural effects of the probes on the potency and efficiency of covalent protein modification. Among the compounds analyzed, a STX-maleimide-coumarin derivative is most effective at irreversibly blocking Na+ conductance when applied to recombinant NaVs and endogenous channels expressed in hippocampal neurons. Mechanistic analysis supports the conclusion that high-affinity toxin binding is a prerequisite for covalent protein modification. Results from these studies are guiding the development of next-generation tool compounds for selective modification of NaVs expressed in the plasma membranes of cells.

Recent Efforts in Identification of Privileged Scaffolds as Antiviral Agents

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Recent Efforts in Identification of Privileged Scaffolds as Antiviral Agents


Abstract

Viral infections are the most important health concern nowadays to mankind, which is unexpectedly increasing the health complications and fatality rate worldwide. The recent viral infection outbreak developed a pressing need for small molecules that can be quickly deployed for the control/treatment of re-emerging or new emerging viral infections. Numerous viruses, including the human immunodeficiency virus (HIV), hepatitis, influenza, SARS-CoV-1, SARS-CoV-2, and others, are still challenging due to emerging resistance to known drugs. Therefore, there is always a need to search for new antiviral small molecules that can combat viral infection with new modes of action. This review highlighted recent progress in developing new antiviral molecules based on natural product-inspired scaffolds. Herein, the structure-activity relationship of the FDA-approved drugs along with the molecular docking studies of selected compounds have been discussed against several target proteins. The findings of new small molecules as neuraminidase inhibitors, other than known drug scaffolds, Anti-HIV and SARS-CoV are incorporated in this review paper.

Regioselective Synthesis of 3‐Substituted Isocoumarin‐1‐imines via Palladium‐Catalyzed Denitrogenative Transannulation of 1,2,3‐Benzotriazin‐4(3H)‐ones and Terminal Alkynes

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Regioselective Synthesis of 3-Substituted Isocoumarin-1-imines via Palladium-Catalyzed Denitrogenative Transannulation of 1,2,3-Benzotriazin-4(3H)-ones and Terminal Alkynes

An efficient palladium-catalyzed denitrogenative transannulation strategy to access various 3-substituted isocoumarin-1-imine frameworks using 1,2,3-benzotriazin-4(3H)-ones and terminal alkynes is described.


Abstract

A palladium-catalyzed denitrogenative transannulation strategy to access various 3-substituted isocoumarin-1-imine frameworks using 1,2,3-benzotriazin-4(3H)-ones and terminal alkynes is described. The reaction is highly regioselective and tolerates a wide range of functional groups. The reaction is believed to proceed via a five-membered palladacycle intermediate extruding environmentally benign molecular nitrogen as a by-product. The utility of this method was showcased through the one-pot synthesis of biologically relevant 3-substituted isocoumarin scaffolds.

Preparation of Some New Pyrazolo[1,5‐a]pyrimidines and Evaluation of Their Antioxidant, Antibacterial (MIC and ZOI) Activities, and Cytotoxic Effect on MCF‐7 Cell Lines

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Preparation of Some New Pyrazolo[1,5-a]pyrimidines and Evaluation of Their Antioxidant, Antibacterial (MIC and ZOI) Activities, and Cytotoxic Effect on MCF-7 Cell Lines


Abstract

This study aims to synthesize some novel pyrazolo[1,5-a]pyrimidine derivatives, and investigate their biological activities. These compounds exhibited good to high antioxidant activities [2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging capabilities]. Among them, Ethyl 5-(2-ethoxy-2-oxoethyl)-7-hydroxy-2-methylpyrazolo[1,5-a]pyrimidine-3-carboxylate (3h) showed the highest antioxidant activity [Half-maximal Inhibitory Concentration (IC50)=15.34 μM] compared to ascorbic acid (IC50=13.53 μM) as a standard compound. Their antibacterial activities were investigated against two Gram-positive bacteria (Bacillus subtilis, and Staphylococcus aureus) and two Gram-negative bacteria (Pseudomonas aeruginosa, and Escherichia coli). The results showed that Ethyl 7-hydroxy-5-phenylpyrazolo[1,5-a]pyrimidine-3-carboxylate (3i) has the best antibacterial activity against Gram-positive B. subtilis [Zone of Inhibition (ZOI)=23.0±1.4 mm, Minimum Inhibitory Concentration (MIC)=312 μM]. Also, the cytotoxicity of these compounds was assessed against breast cancer cell lines [human breast adenocarcinoma (MCF-7)], which 7-Hydroxy-2-methyl-5-phenylpyrazolo[1,5-a]pyrimidine-3-carbonitrile (3f) displayed the most cytotoxicity (IC50=55.97 μg/mL), in contrast with Lapatinib (IC50=79.38 μg/mL) as a known drug.

DFT Mechanistic Insights into the Ni(II)‐Catalyzed Enantioselective Arylative Cyclization of Tethered Allene‐Ketones

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DFT Mechanistic Insights into the Ni(II)-Catalyzed Enantioselective Arylative Cyclization of Tethered Allene-Ketones

A detailed DFT mechanistic investigation on redox neutral nickel(II)-catalyzed arylative cyclization reactions of a tethered allene-ketone with arylboronic acids. This work highlights that the transformation consists of three key elementary steps: (i) base-free transmetalation, (ii) cationic terminal allene insertion, and (iii) a diastereo- and enantio-determining cyclization step.


Abstract

Density functional theory (DFT) has provided a detailed mechanistic picture for the redox neutral nickel(II)-catalyzed arylative cyclization reactions of a tethered allene-ketone with arylboronic acids. A mechanistic rationale for the high diastereo- and enantioselectivity achieved experimentally at high reaction temperature was uncovered through modeling the reaction with a chiral ligand and the predicted stereochemical outcome corroborates with experimental results. An unprecedented mechanism for the base-free organoboron transmetalation was revealed and the regioselectivity of migratory insertion of tethered allene-ketones as well as the stability of the possible allylnickel isomers (σ-allyl vs π-allyl) were clarified. The multifaceted nature of the reaction is revealed with certain elementary steps preferring cationic compared to the neutral state.

Advances in the Research of Photo, Electrical, and Magnetic Responsive Smart Superhydrophobic Materials: Synthesis and Potential Applications

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Advances in the Research of Photo, Electrical, and Magnetic Responsive Smart Superhydrophobic Materials: Synthesis and Potential Applications

This paper presents recent advances in photo, electro, and magneto responsive smart superhydrophobic materials, focusing on the synthesis, modification, properties, and responsive behaviours of photo, electro, and magneto responsive smart superhydrophobic materials in response to different external stimuli, and also explores the challenges associated with different types of responsive superhydrophobic materials, as well as the unique prospects for the application of photo, electro, and magneto responsive superhydrophobic materials.


Abstract

With the rapid advancement of technology, the wettability of conventional superhydrophobic materials no longer suffice to meet the demands of practical applications. Intelligent responsive superhydrophobic materials have emerged as a highly sought-after material in various fields. The exceptional superhydrophobicity, reversible wetting, and intelligently controllable characteristics of these materials have led to extensive applications across industries, including industry, agriculture, defense, and medicine. Therefore, the development of intelligent superhydrophobic materials with superior performance, economic practicality, enhanced sensitivity, and controllability assumes utmost importance in advancing technology worldwide. This article provides a summary of the wettability principles of superhydrophobic surfaces and the mechanisms behind intelligent responsive superhydrophobicity. Furthermore, it reviews and analyzes the recent research progress on light, electric, and magnetic responsive superhydrophobic materials, encompassing aspects such as material synthesis, modification, performance, and responses under diverse external stimuli. The article also explores the challenges associated with different types of responsive superhydrophobic materials and the unique application prospects of light, electric, and magnetic responsive superhydrophobic materials. Additionally, it outlines the future directions for the development of intelligent responsive superhydrophobic materials.