Quaternary Amino Research Articles

Asymmetric Synthesis of Quaternary Amino Acid Esters

Asymmetric Synthesis of Quaternary Amino Acid Esters

High-efficiency removal of methcathinone from water using a novel DES modified magnetic biochar nanocomposite

Deep eutectic solvent (DES), an environmentally friendly solvent, has drawn the growing interest of the academic community due to its distinctive physicochemical properties and widespread applications. In this work, magnetic biochar modified with DES (DES-MBC) has been fabricated and utilized to efficiently remove methcathinone from water. Batch experiments and density functional theory (DFT) simulations were utilized to explore the adsorption performance and mechanism of DES-MBC. Under optimal conditions, the removal rates of DES-MBC were highly remarkable with 93.26% and 95.85% in water containing methcathinone of 0.5 mg·L−1 and 1.0 mg·L−1, respectively. DFT simulations revealed that DES incorporation lowered the HOMO-LUMO energy gap (ΔEgap) and introduced additional reaction sites (e. g. hydroxyl groups and quaternary amino groups) which could react with methcathinone to increase the adsorption capacity of DES-MBC. Combining the results of experiments and simulations, the main removal mechanism between methcathinone and DES-MBC were electrostatic interaction, hydrogen bond and π-π interaction. In conclusion, DES modification was an effective strategy to enhance the adsorption capacity for methcathinone from water in practical applications. This study will contribute to the deep and extensive understanding of the microscopic adsorption mechanism so as to help optimize and develop more excellent adsorbents.

Construction of Quaternary Allylic Amino Acid Derivatives through Palladium-Catalyzed Allylic Alkylation Reaction of Azlactones with Vinyl Aziridine

AbstractA highly efficient Pd-catalyzed allylic alkylation reaction of azlactones with vinyl aziridine has been achieved for the first time to access­ functionalized quaternary allylic amino acid derivatives (17 examples, up to 89% yield and 80% ee). Moreover, the broad scope and easy transformations of the products reinforce the value of this approach, which can enrich the chemistry of quaternary allylic amino acid derivatives.

Nickel/Copper-Catalyzed Synthesis of Tetrasubstituted Amino Acids

Key words nickel catalysis - copper catalysis - benzylation - aldimine esters - quaternary amino acids

Molecular recognition between membrane epitopes and nearly free surface silanols explains silica membranolytic activity

Inhaled crystalline silica causes inflammatory lung diseases, but the mechanism for its unique activity compared to other oxides remains unclear, preventing the development of potential therapeutics. Here, the molecular recognition mechanism between membrane epitopes and “nearly free silanols” (NFS), a specific subgroup of surface silanols, is identified and proposed as a novel broad explanation for particle toxicity in general. Silica samples having different bulk and surface properties, specifically different amounts of NFS, are tested with a set of membrane systems of decreasing molecular complexity and different charge. The results demonstrate that NFS content is the primary determinant of membrane disruption causing red blood cell lysis and changes in lipid order in zwitterionic, but not in negatively charged liposomes. NFS-rich silica strongly and irreversibly adsorbs zwitterionic self-assembled phospholipid structures. This selective interaction is corroborated by density functional theory and supports the hypothesis that NFS recognize membrane epitopes that exhibit a positive quaternary amino and negative phosphate group. These new findings define a new paradigm for deciphering particle-biomembrane interactions that will support safer design of materials and what types of treatments might interrupt particle-biomembrane interactions.

Effect of Cyclodextrins on the Biofilm Formation Capacity of Pseudomonas aeruginosa PAO1.

Quorum sensing (QS) is a population-density-dependent communication process of microorganisms to coordinate their activities by producing and detecting low-molecular-weight signal molecules. In pathogenic bacteria, the property controlled by QS is often related to infectivity, e.g., biofilm formation. Molecular encapsulation of the QS signals is an innovative method to prevent the signals binding to the receptors and to attenuate QS. Cyclodextrins (CDs) may form an inclusion complex with the signals, thus reducing the communication (quorum quenching, QQ). A systematic study was performed with α-, β-cyclodextrin, and their random methylated, quaternary amino and polymer derivatives to evaluate and compare their effects on the biofilm formation of Pseudomonas aeruginosa. To examine the concentration-, temperature- and time-dependency of the QQ effect, the CDs were applied at a 0.1–12.5 mM concentration range, and biofilm formation was studied after 6, 24, 48 and 72 h at 22 and 30 °C. According to the results, the QS mechanism was significantly inhibited; the size of the cavity, the structure of the substituents, as well as the monomeric or polymeric character together with the concentration of the CDs have been identified as key influencing factors of biofilm formation. Statistically determined effective concentration values demonstrated outstanding efficiency (higher than 80% inhibition) of α-CD and its random methylated and polymer derivatives both on the short and long term. In summary, the potential value of CDs as inhibitors of QS should be considered since the inhibition of biofilm formation could significantly impact human health and the environment.

Scaling-resistant anion-exchange membrane prepared by in situ modification with a bifunctional polymer containing quaternary amino groups

Membrane scaling and subsequent cleaning efficiency are major factors limiting commercial applications of electrodialysis. The generation of OH− ions during water splitting at the membrane interface promotes scaling formation. We report a modification of a commercial anion-exchange membrane, which improves its scaling resistance by reducing the water splitting rate. This is achieved by replacing the weakly basic amino groups on the surface of membrane with quaternary ones that do not have catalytic activity with respect to water splitting. We have carried out a comprehensive study of membranes modified by ex situ, and new membranes, for the first time modified in situ, directly inside the electrodialyzer. The in situ modified membranes were found to exhibit better properties in decreasing the water splitting rate, which, in turn, significantly reduces the scale formation on the surface facing the concentration chamber.

Detection and determination of C12-, C14-, C16-alkyldimethylamines in human blood using gas chromatography-mass spectrometry.

N,N-Dimethyldodecylamine is produced from lauryl alcohol and dimethylamine. C12-C16 alkyldimethylamines are used as intermediates for the manufacture of amineoxides and quaternary amino compounds. In the present study a gas chromatography-mass spectrometry (GC/MS) method for the determination of C12-C16 alkyldimethylamines in blood was developed and validated. The reason for this study was the detection of the above compounds in the postmortem blood sample of a fatal suicide case. Analysis of amines was performed using a gas chromatograph (Agilent Technologies 7890A) with an MS 5975C inrXL, EI/CI MSD with triple-axis detector in selected ion monitoring mode, after liquid-liquid extraction. Four different organic solvents (butyl acetate, ethyl acetate, n-hexane and n-heptane) were used for the optimization of the extraction procedure, resulting in ethyl acetate being the solvent of choice for the extraction procedure. A QuEChERS step was applied (20 mg of MgSO4 , 5mg of NaCl) to 1mL of blood and pH was adjusted at 12 (K2 CO3 buffer solution). After the addition of the extraction solvent, samples were vortexed, centrifuged and directly injected into the GC/MS system. In validation, the method was found to be selective and sensitive (limit of detection from 0.3 to 0.5ng/mL, limit of quantitation from 10.0 to 20.0ng/mL), whilst validation included recovery, stability, accuracy and precision (relative standard deviation). Validation results were found satisfactory: intra- and interday precision ranged from 0.4% to 2% and from 0.6% to 1.9% respectively, while intra- and interday accuracy ranged from 87% to 109% and from 86% to112.8%. C12-C16 alkyldimethylamines were detected in blood samples at a concentration of 8.39 μg/mL (C12), 3.01 μg/mL (C14) and 0.42 μg/mL (C16). A rapid, sensitive and reliable method was developed for the determination of C12-C16 alkyldimethylamines in postmortem blood, after optimization of the sample preparation procedure, and finally successfully applied to a real postmortem blood sample from a fatal case involving these compounds.

Chiral Bicyclic Imidazole-Catalyzed Direct Enantioselective C -Acetylation of Indolones

Chiral Bicyclic Imidazole-Catalyzed Direct Enantioselective <i>C</i> -Acetylation of Indolones

Insight into the Adsorption Behavior of Rhenium(Vii) Onto Primary, Secondary, Tertiary and Quaternary Amino Groups in Polymeric Adsorbents: Batch Experiments, Spectroscopic Analyses, and Theoretical Computations

Insight into the Adsorption Behavior of Rhenium(Vii) Onto Primary, Secondary, Tertiary and Quaternary Amino Groups in Polymeric Adsorbents: Batch Experiments, Spectroscopic Analyses, and Theoretical Computations

Delignification of unbleached pulp by ternary deep eutectic solvents

Abstract The processing of lignocellulosic materials is very limited because of their low solubility in water and some organic solvents. Fifteen ternary deep eutectic solvents (DESs) were prepared and tested as solvents suitable for delignification of unbleached pulp. The selected ternary DESs are composed of quaternary ammonium salts and amino acids as hydrogen-bond acceptors, and organic acids and polyvalent alcohols as hydrogen bond donors, with molar ratios varying for the individual components. The delignification efficiency is significantly influenced by the degree of penetration of the solvent into the pulp fibre structure. Therefore, the density and viscosity analysis of individual solvents was performed. Unbleached beech pulp with initial kappa number 13.9 was treated with the prepared DESs. The kappa number indicates the residual lignin content or the bleachability of pulp. The efficiency of the solvents ranged from 1.4% to 28.1%. The most suitable for the pretreatment of fibres, based on lignin removal efficiency, were found to be three DESs, in the following order: malonic acid/choline chloride/1,3-propanediol (1:1:3) &gt; choline chloride/acetamide/lactic acid (1:2:3) &gt; choline chloride/urea/lactic acid (1:2:3).

Amine-Directed Palladium-Catalyzed C-H Halogenation of Phenylalanine Derivatives.

An efficient primary-amine-directed, palladium-catalyzed C-H halogenation (X=I, Br, Cl) of phenylalanine derivatives is reported on a range of quaternary amino acid (AA) derivatives thanks to suitable conditions employing trifluoroacetic acid as additive. The extension of this original native functionality-directed ortho-selective halogenation was even demonstrated with the more challenging native phenylalanine as tertiary AA.

Stability of Properties of a Modified Anion-Exchange Membrane Obtained by Treating the Surface of a Commercial Sample with Bifunctional Polymer Containing Quaternary Amino Groups

Stability of Properties of a Modified Anion-Exchange Membrane Obtained by Treating the Surface of a Commercial Sample with Bifunctional Polymer Containing Quaternary Amino Groups

A comprehensive study of amino acids based ionic liquids as green lubricants for various contacts

In this paper, a group of quaternary ammonium amino acid ionic liquids (QAAA ILs) prepared by coupling the tetrabutylammonium cation with fourteen types of natural amino acids as base lubricant were investigated for steel/steel, steel/copper and steel/aluminum contacts at ambient temperature and elevated temperature. The corrosion resistance and tribological ability of various QAAA ILs was determined. The influences of various anionic structures on kinematic viscosity, corrosivity, thermal stability and tribological properties of the ILs were discussed in detailed. The copper strip corrosion test results showed that the present ILs have been proved to be almost non-corrosive. Tribological behaviors results displayed that the present ILs exhibit extremely eminent friction reduction and antiwear properties. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis revealed that a protective lubricating film is formed on the surface of contact mainly through a polarity induced physical adsorption when QAAA ILs are selected as neat lubricants, which plays a key role in reducing friction and wear between the moving mechanical interface.

δ-Valerolactamic Quaternary Amino Acid Derivatives: Enantiodivergent Synthesis and Evidence for Stereodifferentiated β-Turn-Inducing Properties.

Enantiopure (R) and (S) cyclic α,α-disubstituted amino acid derivatives displaying a δ-valerolactam side chain were prepared from a common isoxazolidine precursor. The (R)-configured δ-valerolactam 11 was converted into diastereoisomeric pseudopeptides to investigate its ability to induce secondary structures in peptidomimetics. Conformational studies of these pseudopeptides were carried out in the solid state (X-ray diffraction), in solution (NMR analyses), and in silico (computer-aided conformational analysis), which demonstrated that such quaternary amino acids induce β-turn conformations stable enough to be retained in polar media (DMSO). Incorporation of this new type of α,α-disubstituted amino acid into a representative pseudopeptidic sequence by N- then C-elongation and N-debenzylation is also described herein and could serve for the synthesis of various structured peptidomimetics.

Towards a Strategy for the Synthesis of Polymeric Ionic Liquids with a Bulk Anion in Various Reaction Media

The interest in polymerizable ionic liquids of researchers is due to their unique properties, such as good thermal stability, low vapor pressure, and wide potential window of stability. The complex of these properties determines the prospect of using ionic liquids and polymers based on them in the technology of membrane separation. This article describes the synthesis of monomeric ionic liquids (IL) containing quaternary amino groups, pyridine, and imidazole groups based on vinyl benzyl chloride (conversion was 95%). Further, on their basis, polymer ionic liquids were obtained by the method of free radical polymerization with bulky anionic substituents. Proof of the formation of polimeric IL was carried out by NMR and FTIR spectroscopy methods. The molecular weight of the IL was determined by gel permeation chromatography and reached ~ 140,000. An anion exchange reaction was carried out to replace the Cl anion with Tf2N.

1,3‐Dipolar Cycloaddition between Dehydroalanines and C,N‐Cyclic Azomethine Imines: Application to Late‐Stage Peptide Modification

AbstractA non‐catalytic, mild, and easy‐to‐handle protecting group switched 1,3‐dipolar cycloaddition (1,3‐DC) between bi‐ or mono‐N‐protected Dha and C,N‐cyclic azomethine imines, which afford various quaternary amino acids with diverse scaffolds, is disclosed. Specifically, normal‐electron‐demand 1,3‐DC reaction occurs between bi‐N‐protected Dha and C,N‐cyclic azomethine imines, while inverse‐electron‐demand 1,3‐DC reaction occurs between mono‐N‐protected Dha and C,N‐cyclic azomethine imines. Above all, the reactions can be carried out between peptides with Dha residues at the position of interest and C,N‐cyclic azomethine imines, both in homogeneous phase and on resins in SPPS. It provides a new toolkit for late‐stage peptide modification, labeling, and peptide–drug conjugation. To shed light on the high regioselectivity of the reaction, DFT calculations were carried out, which were qualitatively consistent with the experimental observations.

1,3-Dipolar Cycloaddition between Dehydroalanines and C,N-Cyclic Azomethine Imines: Application to Late-Stage Peptide Modification.

A non-catalytic, mild, and easy-to-handle protecting group switched 1,3-dipolar cycloaddition (1,3-DC) between bi- or mono-N-protected Dha and C,N-cyclic azomethine imines, which afford various quaternary amino acids with diverse scaffolds, is disclosed. Specifically, normal-electron-demand 1,3-DC reaction occurs between bi-N-protected Dha and C,N-cyclic azomethine imines, while inverse-electron-demand 1,3-DC reaction occurs between mono-N-protected Dha and C,N-cyclic azomethine imines. Above all, the reactions can be carried out between peptides with Dha residues at the position of interest and C,N-cyclic azomethine imines, both in homogeneous phase and on resins in SPPS. It provides a new toolkit for late-stage peptide modification, labeling, and peptide-drug conjugation. To shed light on the high regioselectivity of the reaction, DFT calculations were carried out, which were qualitatively consistent with the experimental observations.

Scalable synthesis and coupling of quaternary α-arylated amino acids: α-aryl substituents are tolerated in α-helical peptides.

Quaternary amino acids are important tools for the modification and stabilisation of peptide secondary structures. Here we describe a practical and scalable synthesis applicable to quaternary alpha-arylated amino acids (Q4As), and the development of solid-phase synthesis conditions for their incorporation into peptides. Monomeric and dimeric α-helical peptides are synthesised with varying degrees of Q4A substitution and their structures examined using biophysical methods. Both enantiomers of the Q4As are tolerated in folded monomeric and oligomeric α-helical peptides, with the (R)-enantiomer slightly more so than the (S).

Progress of cationic gene delivery reagents for non-viral vector.

Gene delivery systems play a vital role in gene therapy and recombinant protein production. The advantages of using gene delivery reagents for non-viral vector include the capacity to accommodate a large packaging load and their low or absent immunogenicity. Furthermore, they are easy to produce at a large scale and preserve. Gene delivery reagents for non-viral vector are commonly used for transfecting a variety of cells and tissues. It is mainly composed of liposomes and non-liposome cationic polymers. According to the different head structures used, the non-viral cationic transfection reagents include a quaternary ammonium salt, amine, amino acid or polypeptide, guanidine salt, and a heterocyclic ring. This article summarizes these approaches and developments of types and components of transfection reagents and optimization of gene delivery. The optimization of mammalian cell transient recombinant protein expression system and cationic reagents for clinical or clinical trials are also discussed.