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Monthly Archives: March 2024
Synthesis of R‐GABA Derivatives via Pd(II) Catalyzed Enantioselective C(sp3)‐H Arylation and Virtual Validation with GABAB1 Receptor for Potential leads
GABA (γ-amino butyric acid) analogues like baclofen, tolibut, phenibut, etc., are well-known GABAB1 inhibitors and pharmaceutically important drugs. However, there is a huge demand for more chiral GABA aryl analogues with promising pharmacological actions. Here, we demonstrate the chiral ligand acetyl-protected amino quinoline (APAQ) mediated enantioselective synthesis of GABAB1 inhibitor drug scaffolds from easily accessible GABA via Pd-catalyzed C(sp3)-H activation. The synthetic methodology shows moderate to good yields, up to 74% of ee. We have successfully demonstrated the deprotection and removal of the directing group to synthesize R-tolibut in 86% yield. Further, we employed computation to probe the binding of R-GABA analogues to the extracellular domain of the human GABAB1 receptor. Our Rosetta-based molecular docking calculations show better binding for four R-enantiomers of GABA analogues than R-baclofen and R-phenibut. In addition, we employed GROMACS MD simulations and MMPB(GB)SA calculations to identify per-residue contribution to binding free energy. Our computational results suggest analogues (3R)-4-amino-3-(3,4-dimethylphenyl)butanoic acid, (3R)-4-amino-3-(3-fluorophenyl)butanoic acid, (3R)-3-(4-acetylphenyl)-4-aminobutanoic acid, (3R)-4-amino-3-(4-methoxyphenyl)butanoic acid, and (3R)-4-amino-3-phenylbutanoic acid are potential leads which could be synthesized from our methodology reported here.
[ASAP] In Silico Study on a Binding Mechanism of ssDNA Aptamers Targeting Glycosidic Bond-Containing Small Molecules
Analytical Chemistry
DOI: 10.1021/acs.analchem.4c00927
[ASAP] Diffusion of Multiple Species Resolved by Fluorescence Lifetime Recovery after Photobleaching (FLRAP)
Analytical Chemistry
DOI: 10.1021/acs.analchem.3c05181
Influence of Acid‐Base Characteristics of Different Structural‐Type Zeolites (FER, MFI, FAU, BEA) on Their Activity and Selectivity in Isobutanol Dehydration
The different structural-type zeolites (FER, MFI, FAU, BEA) are investigated as catalysts in (bio)isobutanol conversion into linear butenes. The zeolites’ structure and morphology are confirmed by XRD, N2 (77 K) ad(de)sorption, SEM, EDX, XPS, and 27Al, 29Si, 1H MAS NMR, 1H-29Si CP MAS NMR. The nature and strength of acid-base sites are determined by FTIR spectroscopy of adsorbed pyridine, potentiometric titration, and TPD of NH3/CO2/H2O with MS control. The acid-base properties of the zeolites' surfaces influence their catalytic properties in the target process. The higher selectivity towards linear butene isomers achieved over FER and MFI can be explained by the high strength and density of Brønsted acid sites (over 90% of the total surface acidity). MFI might be regarded as a potential material for the creation of novel catalysts for isobutanol conversion into linear butenes at moderate temperatures (448-473 K) since it offers greater operating stability throughout the process.
[ASAP] Simultaneous SERS Sensing of Cysteine and Homocysteine in Blood Based on the CBT-Cys Click Reaction: Toward Precisive Diagnosis of Schizophrenia
Analytical Chemistry
DOI: 10.1021/acs.analchem.4c00395
Palladium(II) NCS‐Pincer Complexes Mediated Regioselective Cross Dehydrogenative Alkenation of 2‐Arylthiophenes
In this report, we have synthesized two NCS pincer ligands by the Schiff base reaction of 3-((phenylthio)methoxy)benzaldehyde (P) with alkyl amines (tbutylamine (L1) and 1-adamantylamine (L2)). The palladium pincer complexes (tbutylamine = C1 and 1-adamantylamine = C2) of these ligands were synthesized by their reaction with PdCl2(CH3CN)2. The newly synthesized ligands and complexes were characterized using various techniques such as 1H, 13C{1H} Nuclear Magnetic Resonance (NMR), Ultraviolet–visible (UV-Visible), Fourier Transform Infrared (FTIR) Spectroscopy, and High-Resolution Mass Spectrometry (HRMS). The structure of ligand and its coordination mode with palladium precursor were studied with the help of single-crystal X-ray diffraction. The complexes showed distorted square planar geometry around the palladium center. The palladium pincer complexes were used as catalysts for the regioselective cross-dehydrogenative alkenation of 2-arylthiophene derivatives. The complex C2, where sterically bulky adamantyl ligand is part of the side arm showed a higher yield of alkenation reaction. Only 2.5 mol% catalyst loading was sufficient to achieve 74-95% yields of desired products with excellent functional group tolerance under mild reaction conditions. The poisoning experiments (PPh3 and Hg) showed the homogeneous nature of the catalytic process. The plausible mechanism of the reaction was proposed based on the control experiments and time-dependent HRMS studies.
Synthesis, Characterization, and Polymorphism of [H3O][NbF6]: A Polar and Possibly Ferroelectric Oxonium Salt
![Synthesis, Characterization, and Polymorphism of [H3O][NbF6]: A Polar and Possibly Ferroelectric Oxonium Salt](https://chemistry-europe.onlinelibrary.wiley.com/cms/asset/4af5b24d-c3f1-4417-a163-b6bf55f32811/ejic202400015-toc-0001-m.png)
[H3O][NbF6] was synthesized and characterized. At room temperature, it adopts a polar structure with the dipole momentum of the [H3O]+ ions directed along the polar axis. A phase transition at 363 K leads to a plastic high-temperature polymorph hinting towards potential ferroelectric properties of the compound as the [H3O]+ and [NbF6]− ions are able to rotate freely. A second phase transition at 137 K leads to a cubic non-centrosymmetric low-temperature polymorph.
Abstract
[H3O][NbF6] was obtained from the controlled hydrolysis of NbF5 in anhydrous liquid HF. It adopts a polar, orthorhombic crystal structure with space group Iba2 (no. 45, oI88) at room temperature. A first-order phase transition at 137 K leads to a cubic non-centrosymmetric polymorph in space group I213 (no. 199, cI88). This low-temperature modification results from a distinct rotation of the [H3O]+ cations canceling their polar orientation in the room temperature phase. Quantum-chemical calculations estimate a rotational barrier between 5.8 to 6.4 kJ/mol. At a temperature of 363 K, the compound adopts a centrosymmetric, cubic crystal structure in space group Pm m (no. 221, cP11) that shows rotational disorder of cations and anions. The transition from the polar phase at room temperature to the centrosymmetric phase at high temperature not only reveals the plastic nature of the high-temperature structure but also hints at potential ferroelectric properties, underscoring the multifaceted behavior of [H3O][NbF6] across different temperature regimes.
Amino Acid‐Mediated Formation of Zirconia Nanoparticles and their Transparent Dispersions
We present a straightforward one-pot hydrothermal method for the synthesis of zirconia nanodispersions, leading to the formation of stable sols. By simply varying the nature of the stabilizer used, one can obtain a large variety of objects with different sizes, shapes and crystallinities. Our results demonstrate the crucial role played by aliphatic amino acids both during the formation of the objects and after, since their interaction with the surface of the inorganic crystals influences strongly the optical properties and colloidal stability of the latter. Importantly, the versatility of this method allows for the introduction of different dopants, increasing substantially the scope of applications that can be achieved with such nanoscale oxides. The high transparencies and the easy dispersibility of nanoparticles in different liquid matrixes ensure the formation of zirconia-based nanocomposites and ceramics with outstanding optical features for the orthopedic, dental, photonics and chemical sectors. This method can be easily scaled up, being already available for the production of high-quality zirconia nanodispersions at the industrial level.
Carbon and nitrogen‐co‐doped Se/NiSe2/CoSe2 nanocomposite as superior performance electrode material in hybrid supercapacitors
Metal selenides are essential electrode materials for promising electrochemical energy storage with comparable or improved electrochemical performance than metal oxides. Herein, Se/NiSe2/CoSe2 (S/NS/CS) is fabricated using a solvothermal approach with the assistance of polyethyleneimine, followed by annealing at different temperatures (300, 400, 500, and 600°C) for one hour under an argon atmosphere. After annealing, all electrodes’ physical and electrochemical properties were examined, which determined that the best electrode is NiCo2O4/NiO (NCO/NO) formed at 500°C. Another hydrothermal method uses NCO/NO with SeO2 as a selenium source to prepare S/NS/CS nanocomposite, with a specific surface architecture that enables easy ion movement and strong conductivity, giving it exceptional electrochemical energy storage properties. It exhibited a remarkable capacitance of 468 F g−1 at a current density of 0.5 A g−1. For practical applications, the hybrid S/NS/CS//AC device was designed using S/NS/CS as a positive electrode and commercial activated carbon (AC) as a negative electrode. The asymmetric device demonstrated an excellent capacitance of 142 F g−1 (189 C g−1) and a superb specific energy of 44 Wh kg−1 at a specific power of 840 W kg−1 at a current density of 1 A g−1, providing 80% capacity retention and 100% coulombic efficiency after 5000 cycles.