Revisiting Dimorphs of 4‐n‐octyloxybenzoic Acid: Contrasting Mechanical Property and Surface Wettability

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Revisiting Dimorphs of 4-n-octyloxybenzoic Acid: Contrasting Mechanical Property and Surface Wettability

Contrasting mechanical property and surface wettability of the single crystals of concomitant dimorphs of a well-known mesogen n-octyloxybenzoic acid is discovered, and structure-property correlation is established.


Abstract

4-n-octyloxy benzoic acid is known to exhibit liquid crystalline properties, and under normal pressure and temperature conditions, it exists as at least two crystalline polymorphs. We revisited the system and discovered that single crystals of one of the polymorphs display plastic deformation, whereas the other is brittle. n-octyl chains are arranged in an end-to-end fashion, forming slip planes in the plastically deformable polymorph, whereas they are interdigitated in the crystal structure of the brittle polymorph. Due to the difference in the arrangement of the −COOH group and alkyl chains, the major faces of the crystals of both polymorphs possess significant differences in the wettability towards moisture.

Construction of Synergistic Co/CoO Interface to Enhance Hydrogenation Activity of Ethyl Lactate to 1,2‐Propanediol

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Construction of Synergistic Co/CoO Interface to Enhance Hydrogenation Activity of Ethyl Lactate to 1,2-Propanediol

A selective and stable hydrogenation of EL to diol is achieved over a bifunctional Co/CoO catalyst derived from CoAl−LDH, where the synergetic catalysts are found to promote the hydrogenation at the unique Co/CoO interfacial structure with the activation of H2 on metallic Co0 and strong adsorption of EL via hydroxyl groups over CoO site.


Abstract

The development of effective and stable non-precious catalysts for hydrogenation of ester to diols remains a challenge. Herein, the catalytic hydrogenation of ethyl lactate (EL) to 1,2-propanediol (1,2-PDO) with supported Co catalysts derived from layered double hydroxides (LDHs) is investigated. Catalytic tests reveal that LDH-derived Co catalysts exhibit the best catalytic performance with 98 % of EL conversion and >99 % of 1,2-PDO selectivity at mild conditions, compared with other Co catalysts (supported on Al2O3, and TiO2) and LDH-derived Cu catalysts. Due to the strong interaction among Co and Al matrix, the main composition is metallic Co0 and CoO after reduction at 600 °C. Besides, the catalyst shows good recyclability in the liquid phase hydrogenation. The superior catalytic performance can be attributed to the synergistic effect between Co0 and CoO, in which H2 molecule is activated on Co0 and EL is strongly adsorbed on CoO via hydroxyl groups.

Carbon‐Sulfur Bond Cleavage in Methanesulfonate on Diorganotin Quinaldate Platform – Synthesis and Characterization of [(n‐Bu2SnL)2SO4]

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Carbon-Sulfur Bond Cleavage in Methanesulfonate on Diorganotin Quinaldate Platform – Synthesis and Characterization of [(n-Bu2SnL)2SO4]

Several new mixed ligand diorganotin complexes, [(n-Bu2SnL1−3)2SO4] and [(Me2Sn)2(L2)3(OSO2Me)] (HL= quinadic acids) have been synthesized and structurally characterized by X-ray crystallography.


Abstract

The synthesis of mixed ligand di-n-butyltin complexes, [(n-Bu2SnL1−3)2SO4], 2–4 (HL1−3=2-quinoline/ 1-isoquinoline/ 4-methoxy-2-quinoline carboxylic acid) has been realized by reacting n-Bu2Sn(OMe)OSO2Me, 1 a with the corresponding quinaldic acid under solvothermal conditions. The observed transformation of methane sulfonate to sulfate anion represents a rare example of C−S bond cleavage on the organotin scaffolds, n-Bu2Sn(L1−3)OSO2Me, which have been identified as en route intermediates by NMR and X-ray crystallography. Analogous reaction when extended with Me2Sn(OMe)OSO2Me, 1 b and HL2 yields [(Me2Sn)2(L2)3(OSO2Me)], 5 as partially disproportionated product of Me2Sn(L2)OSO2Me. The solid-state structures of 2–5 reveal variable modes of coordination of the ligands to afford molecular and polymeric motifs.

Organocatalytic Synthesis and DNA Interactive Studies of New 1,2,3‐triazolyl‐thiazolidines Hybrids

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Organocatalytic Synthesis and DNA Interactive Studies of New 1,2,3-triazolyl-thiazolidines Hybrids

The organocatalyzed reaction between thiazolidine-3-carboxylates and aryl azides resulted in the metal-free synthesis of novel 1,2,3-triazolyl-thiazolidine hybrids in good yields. Spectroscopic methods (absorption and emission), viscosimetry, and molecular docking were employed to assess the interactions between the synthesized compounds and DNA, revealing promising results for the development of novel therapeutic agents targeting DNA-related processes.


Abstract

An organocatalytic [3+2] cycloaddition reaction between thiazolidine-containing β-ketoester 1 and aryl azides 2 was employed to synthesize new 1,2,3-triazolyl-thiazolidine hybrids 3. In this metal-free approach, twelve compounds were isolated in yields ranging from 23 % to 96 % by using diethylamine (10 mol%) and DMSO at 75 °C for 24 hours. DNA-binding assays were conducted through absorption, emission spectroscopy and viscosimetry analysis, to evaluate the interaction capacity of the studied derivatives with nucleic acids. All the synthesized compounds were evaluated for their interactions with a specific group of compounds containing the pharmacophoric groups triazole and thiazolidine through a molecular docking speculative study, aimed at identifying the interaction profile of these compounds with DNA. The obtained results suggest that 1,2,3-triazolyl-thiazolidine hybrids could be a promising approach in the development of novel therapeutic agents targeting DNA-related processes.

Selective Aza‐Michael Addition to Dehydrated Amino Acids in Natural Antimicrobial Peptides

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Selective Aza-Michael Addition to Dehydrated Amino Acids in Natural Antimicrobial Peptides

Antimicrobial resistance is an urgent global public health problem that has made the search for new antibiotics essential. Ribosomally synthesized and post-translationally modified peptides are a promising new class of antibiotics and in this work, we report site-selective modification of their dehydroamino acids by β-amination in order to increase water solubility: the singly modified thiopeptide Thiostrepton showed an increase up to 35-fold and minimum inhibitory concentration tests demonstrated that the antimicrobial activity was still good, albeit lower than the natural peptide.


Abstract

We report the efficient and site selective modification of non-canonical dehydroamino acids in ribosomally synthesized and post-transationally modified peptides (RiPPs) by β-amination. The singly modified thiopeptide Thiostrepton showed an up to 35-fold increase in water solubility, and minimum inhibitory concentration (MIC) assays showed that antimicrobial activity remained good, albeit lower than the unmodified peptide. Also the lanthipeptide nisin could be modified using this method.

Identification, characterization and application of M16AT, a new organic solvent–tolerant (R)–enantio–selective type IV amine transaminase from Mycobacterium sp. ACS1612

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Identification, characterization and application of M16AT, a new organic solvent–tolerant (R)–enantio–selective type IV amine transaminase from Mycobacterium sp. ACS1612

A new (R)-selective amine transaminase (R-ATA) from Mycobacterium sp. ACS1612 was identified via in silico prediction combined with genome and protein database information. The newly identified and characterized R-ATA displayed a broad substrate spectrum and strong tolerance to organic solvents. Moreover, the synthetic applicability of M16AT was demonstrated by the asymmetric synthesis of (R)-fendiline.


Abstract

Biocatalysis has emerged as a powerful alternative to traditional chemical methods, especially for asymmetric synthesis. As biocatalysts usually exhibit excellent chemical, regio- and enantioselectivity, they facilitate and simplify many chemical processes for the production of a broad range of products. Here, a new biocatalyst called, R-selective amine transaminases (R-ATAs), was obtained from Mycobacterium sp. ACS1612 (M16AT) using in–silico prediction combined with a genome and protein database. A two–step simple purification process could yield a high concentration of pure enzyme, suggesting that industrial application would be inexpensive. Additionally, the newly identified and characterized R-ATAs displayed a broad substrate spectrum and strong tolerance to organic solvents. Moreover, the synthetic applicability of M16AT has been demonstrated by the asymmetric synthesis of (R)-fendiline from of (R)-1-phenylethan-1-amine.

Miquelianin: primary antioxidant power and Mpro SARS‐CoV‐2 non‐covalent inhibition capabilities from computational investigations

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The antioxidant power of quercetin-3-O-glucuronide (miquelianin) has been studied, at the density functional level of theory, in both lipid-like and aqueous environments. In the aqueous phase, the computed pKa equilibria allows the identification of the neutral and charged species present in solution that can react with the •OOH radical. The Hydrogen Atom Transfer (HAT), Single Electron Transfer (SET) and Radical Adduct Formation (RAF) mechanisms were considered and the individual, total and fraction corrected total rate constants were obtained. Potential non covalent inhibition of Mpro from SARS-CoV-2 by miquelianin has been also been evaluated.

The Biocatalytic Potential of Aromatic Ammonia‐Lyase from Loktanella atrilutea

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Characterization of the aromatic ammonia-lyase from Loktanella atrilutea (LaAAL) revealed reduced activity towards canonical AAL substrates: L-Phe, L-Tyr, and L-His, contrasted by its pronounced efficiency towards 3,4-dimethoxy-L-phenylalanine. Assessing optimal conditions, LaAAL exhibited maximal activity at pH 9.5 in the ammonia elimination reaction route, distinct from the typical pH ranges of most PALs and TALs. Within the exploration of the ammonia source for the opposite, synthetically valuable ammonia addition reaction, the stability of LaAAL, exhibited a positive correlation with the ammonia concentration, with the highest stability in 4 M ammonium carbamate of unadjusted pH of ~9.5. While the enzyme activity increased with rising temperatures yet, the highest operational stability and highest stationary conversions of LaAAL were observed at 30 °C. The substrate scope analysis highlighted the catalytic adaptability of LaAAL in the hydroamination of diverse cinnamic acids, especially of meta-substituted and di-/multi-substituted analogues, with structural modelling exposing steric clashes between the substrates’ ortho-substituents and catalytic site residues. LaAAL showed a predilection for ammonia elimination, while classifying as a tyrosine ammonia-lyase (TAL) among the natural AAL classes. However, its distinctive attributes, such as genomic context, unique substrate specificity and catalytic fingerprint, suggest a potential natural role beyond those of known AAL classes.

Biocompatible Phosphorescent Ir(III) Complexes for Hypoxia Sensing in PLIM Mode

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Biocompatible Phosphorescent Ir(III) Complexes for Hypoxia Sensing in PLIM Mode

Two new biscyclometalated Ir(III) complexes with diimine ligands were synthesized and utilized to assess the oxygen status of living cells by using time-resolved luminescent microscopy.


Abstract

In this work, two new biscyclometalated Ir(III) complexes with diimine ligands were synthesized. The compounds were characterized by 1D and 2D NMR spectroscopy and HR ESI mass spectrometry. All complexes exhibit efficient phosphorescence with pronounced sensitivity to the presence of oxygen. The photophysical properties of the obtained compounds, including absorption, emission spectra, lifetimes and quantum yields of phosphorescence were measured in various aqueous and model biological media with variations in pH, temperature and at various O2 concentrations. The complexes exhibit a very good sensory response to the changes in oxygen concentration, resulting in an increase in quantum yields and lifetimes by 2.8–5.5 times upon oxygen removal from aerated aqueous solutions. Biological tests with CHO-K1 cell line have shown that these compounds display low toxicity, rapid internalization into cells and localization predominantly in lysosomes. For the most promising complex the phosphorescence lifetime imaging experiments were conducted, revealing that this sensor markedly changes the phosphorescence lifetime values in cells from 1.8 to 4.1 μs upon transition from normoxia to simulated hypoxia. The obtained results indicate that this type of iridium chromophores can be effectively used for assessing the oxygen status of living objects by using time-resolved luminescent microscopy.