Synthesis Features Research Articles

3-Thioxo-3H-indolizinium-1-olates and Related Pseudo-Cross-Conjugated Heterocyclic Mesomeric Betaines: Synthesis and Spectral Features.

The first example of the synthesis of 3-thioxo-3H-indolizinium-1-olates, which further expands a limited class of pseudocross-conjugated heterocyclic mesomeric betaines isoconjugate to odd nonalternant hydrocarbon anion, is reported. These unique, moderately colored heterocyclic products result from a developed three-component reaction of cyclopropenones, pyridines, and sulfur. The protocol is distinguished by simple and mild reaction conditions that avoid expensive reagents or exotic catalysts, exhibiting high functional group tolerance. The broad scope of the reaction is particularly remarkable in light of the dramatic influence of pyridines' substituents on the reactivity of corresponding indolizin-1-ols, the key intermediates that proved to be highly thiophilic. In addition, an oxidative coupling of indolizin-1-ol in situ with p-tropoquinone oxime acetate is discovered. The reaction involves the C3 and C5 positions of the indolizin-1-ol and results in unusual indolizine-aminotropolone combinations. For the 3H-indolizinium-1-olate type of PCC HMBs, some general considerations concerning light absorption and NMR regularities were formulated.

Synthesis, characterization, and crystal features of a mixed ligand binuclear Zinc(II) acyl pyrazolone complex: DFT, Hirshfeld surface analysis and anti-malarial activity evaluation

A novel binuclear [Zn2(L2C)2(HQ)2] complex with mixed ligands was synthesized using pyrazolone-based derivative (L2C) (1-(3-chlorophenyl)-5-hydroxy-3-methyl-1H-pyrazol-4-yl)(4-nitrophenyl)methanone) as the primary ligand and 8-hydroxyquinoline (8-HQ) as the secondary ligand. Single crystal analysis revealed that each zinc(II) atom is penta-coordinated, involving four O-atoms from two pyrazolone ligands and two N-atoms from the 8-hydroxyquinoline. Two hydroxyl O-atoms from the 8-hydroxyquinoline also bridge the zinc atoms, leading to a distorted square pyramidal geometry. The structure of the complex was further characterized using 1H NMR, FT-IR, UV–vis, TGA, and elemental analysis. The compounds’ electronic behaviour, stable geometry, MEP surfaces, and FMO analysis were studied using density functional theory (DFT) at the B3LYP level with the LanL2DZ basis set. These theoretical results were compared with the experimental structural data of the [Zn2(L2C)2(HQ)2] complex. The complex was tested for its ability to inhibit Plasmodium falciparum in vitro.

Fabrication of powder high-entropy TiZrHfNbTa alloy by calcium-hydride method: Synthesis kinetics and structure evolution

High-entropy alloys are currently considered as prospective hydrogen storage materials and getters, which can be utilized to create a high vacuum in specialized devices. To provide high sorption properties, it is crucial to use highly porous materials or powders that makes powder metallurgy an attractive and suitable method. In the current work, a powder high-entropy alloy TiZrHfNbTa was obtained by reducing transition metal oxides with calcium hydride. The mechanism and features of the calcium-hydride synthesis of the high-entropy alloy have been studied. Phase composition has shown to be dependent on holding time at a temperature of 1200 °C. The powder’s structure comprises four BCC solutions based on Nb, Ta, TiZrHf, and TiZrHfNb, when holding time is up to two hours. Prolonged holding leads to more homogeneous structure, and the final product possesses two BCC phases: Ti0.21Zr0.24Hf0.24Nb0.25Ta0.06 (BCC-I: ∼75 wt%) and Ti0.15Zr0.05Hf0.08Nb0.10Ta0.62 (BCC-II: ∼25 wt%). The analysis of BCC-I formation kinetics with the aid of the Avrami equation has shown that a quite prolonged time of around 48 hours is necessary to achieve a single-phase structure of the powder due to the presence of tantalum, which impedes homogenization. Parameter n in the Avrami equation has been determined to be 0.361.

Synthesis and structural features of new push-pull enamines, 5-aryl-3-[(dimethylamino)methylidene]furan-2(3H)-ones

Synthesis and structural features of new push-pull enamines, 5-aryl-3-[(dimethylamino)methylidene]furan-2(3H)-ones

Total Syntheses and Stereochemical Assignment of Acremolides A and B.

The absolute stereochemical configurations of acremolides A and B were predicted by a biochemistry-based rule and unambiguously confirmed through their total syntheses. The features of the total syntheses include sequential Krische's Ir-catalyzed crotylation, Brown's borane-mediated crotylation, Mitsunobu esterification reaction, and cross-metathesis reaction. The efficient total synthesis enabled clear validation of the predicted stereochemistry for acremolides A and B.

Concise Total Syntheses of (-)-Crinipellins A and B Enabled by a Controlled Cargill Rearrangement.

Herein, we report concise total syntheses of diterpene natural products (-)-crinipellins A and B with a tetraquinane skeleton, three adjacent all-carbon quaternary centers, and multiple oxygenated and labile functional groups. Our synthesis features a convergent Kozikowski β-alkylation to unite two readily available building blocks with all the required carbon atoms, an intramolecular photochemical [2 + 2] cycloaddition to install three challenging and adjacent all-carbon quaternary centers and a 5-6-4-5 tetracyclic skeleton, and a controlled Cargill rearrangement to rearrange the 5-6-4-5 tetracyclic skeleton to the desired tetraquinane skeleton. These strategically enabling transformations allowed us to complete total syntheses of (-)-crinipellins A and B in 12 and 13 steps, respectively. The results of quantum chemical computations revealed that the Bronsted acid-catalyzed Cargill rearrangements likely involve stepwise paths to products and the AlR3-catalyzed Cargill rearrangements likely involve a concerted path with asynchronous alkyl shifting events to form the desired product.

Constructing local nanomolecular trap in a scalable, low-cost, and ultramicroporous metal–organic framework for efficient capture of greenhouse gases SF6 and CO2

The capture of sulfur hexafluoride (SF6) and carbon dioxide (CO2) is an important but challenging task for reducing greenhouse gas emission and thereby diminishing negative impacts of global climate change. Herein, we integrated local nanomolecular traps into an inexpensive cobalt-based metal–organic framework (MOF, namely GNU-3) with suitable pore sizes and functional pore surfaces for capturing greenhouse gases. Activated GNU-3a showed good adsorption and separation properties for SF6 and CO2. Especially for SF6, GNU-3a displayed the high SF6/N2 (10:90, v/v) selectivity of 317.6 and SF6 uptake capacity of 2.63mmol/g at 298 K and 1.0 bar. Grand canonical Monte Carlo simulations and first-principles dispersion-corrected density functional theory calculations identified that gas molecules were favorably trapped in polyaromatic ring functionalized channel centers and nanomolecular traps of pore walls by the strong hydrogen bond interactions. Excellent breakthrough results recommend practical separating properties of GNU-3a for binary SF6/N2 and CO2/N2 mixtures, and ternary SF6/CO2/N2 mixtures. Moreover, benefitting from superior features of cheap raw materials and large-scale synthesis, GNU-3 is expected to be applied to practical industrial scenarios. This work may provide insights into constructing prospectively industrial porous MOF adsorbents with optimal pore structures for greenhouse gas capture.

Multi-planar dual adversarial network based on dynamic 3D features for MRI-CT head and neck image synthesis

Objective. Head and neck radiotherapy planning requires electron densities from different tissues for dose calculation. Dose calculation from imaging modalities such as MRI remains an unsolved problem since this imaging modality does not provide information about the density of electrons. Approach. We propose a generative adversarial network (GAN) approach that synthesizes CT (sCT) images from T1-weighted MRI acquisitions in head and neck cancer patients. Our contribution is to exploit new features that are relevant for improving multimodal image synthesis, and thus improving the quality of the generated CT images. More precisely, we propose a Dual branch generator based on the U-Net architecture and on an augmented multi-planar branch. The augmented branch learns specific 3D dynamic features, which describe the dynamic image shape variations and are extracted from different view-points of the volumetric input MRI. The architecture of the proposed model relies on an end-to-end convolutional U-Net embedding network. Results. The proposed model achieves a mean absolute error (MAE) of 18.76±5.167 in the target Hounsfield unit (HU) space on sagittal head and neck patients, with a mean structural similarity (MSSIM) of 0.95±0.09 and a Frechet inception distance (FID) of 145.60±8.38 . The model yields a MAE of 26.83±8.27 to generate specific primary tumor regions on axial patient acquisitions, with a Dice score of 0.73±0.06 and a FID distance equal to 122.58±7.55 . The improvement of our model over other state-of-the-art GAN approaches is of 3.8%, on a tumor test set. On both sagittal and axial acquisitions, the model yields the best peak signal-to-noise ratio of 27.89±2.22 and 26.08±2.95 to synthesize MRI from CT input. Significance. The proposed model synthesizes both sagittal and axial CT tumor images, used for radiotherapy treatment planning in head and neck cancer cases. The performance analysis across different imaging metrics and under different evaluation strategies demonstrates the effectiveness of our dual CT synthesis model to produce high quality sCT images compared to other state-of-the-art approaches. Our model could improve clinical tumor analysis, in which a further clinical validation remains to be explored.

Synthesis features of Li<i>R</i>F<sub>4</sub> (<i>R</i> = Er–Lu) nanoparticles by the high-temperature co-precipitation method and their photoluminescent properties

Synthesis features of Li<i>R</i>F<sub>4</sub> (<i>R</i> = Er–Lu) nanoparticles by the high-temperature co-precipitation method and their photoluminescent properties

Stereoselective Synthesis of Polyketide Segments of Nemamide A and Euglenatides D–E

AbstractA convergent strategy for the stereoselective synthesis of polyketide segments of hybrid natural products nemamide A and euglenatides D–E has been developed for the first time. The salient features of this gram-scale synthesis include Trost–Rychnovsky alkyne rearrangement, HWE olefination, regioselective epoxide ring opening, Prins–Ritter cyclization, and subsequent reductive cleavage of the substituted THP ring. The optimized route is modular and could be tunable to access the other polyketide counterparts of these families of metabolites.

Asymmetric Synthesis and Biological Evaluation of Platensilin, Platensimycin, Platencin, and Their Analogs via a Bioinspired Skeletal Reconstruction Approach.

Platensilin, platensimycin, and platencin are potent inhibitors of β-ketoacyl-acyl carrier protein synthase (FabF) in the bacterial and mammalian fatty acid synthesis system, presenting promising drug leads for both antibacterial and antidiabetic therapies. Herein, a bioinspired skeleton reconstruction approach is reported, which enables the unified synthesis of these three natural FabF inhibitors and their skeletally diverse analogs, all stemming from a common ent-pimarane core. The synthesis features a diastereoselective biocatalytic reduction and an intermolecular Diels-Alder reaction to prepare the common ent-pimarane core. From this intermediate, stereoselective Mn-catalyzed hydrogen atom-transfer hydrogenation and subsequent Cu-catalyzed carbenoid C-H insertion afford platensilin. Furthermore, the intramolecular Diels-Alder reaction succeeded by regioselective ring opening of the newly formed cyclopropane enables the construction of the bicyclo[3.2.1]-octane and bicyclo[2.2.2]-octane ring systems of platensimycin and platencin, respectively. This skeletal reconstruction approach of the ent-pimarane core facilitates the preparation of analogs bearing different polycyclic scaffolds. Among these analogs, the previously unexplored cyclopropyl analog 47 exhibits improved antibacterial activity (MIC80 = 0.0625 μg/mL) against S. aureus compared to platensimycin.

Enzymatic Transglycosylation Features in Synthesis of 8-Aza-7-Deazapurine Fleximer Nucleosides by Recombinant E. coli PNP: Synthesis and Structure Determination of Minor Products.

Enzymatic transglycosylation of the fleximer base 4-(4-aminopyridine-3-yl)-1H-pyrazole using recombinant E. coli purine nucleoside phosphorylase (PNP) resulted in the formation of "non-typical" minor products of the reaction. In addition to "typical" N1-pyrazole nucleosides, a 4-imino-pyridinium riboside and a N1-pyridinium-N1-pyrazole bis-ribose derivative were formed. N1-Pyrazole 2'-deoxyribonucleosides and a N1-pyridinium-N1-pyrazole bis-2'-deoxyriboside were formed. But 4-imino-pyridinium deoxyriboside was not formed in the reaction mixture. The role of thermodynamic parameters of key intermediates in the formation of reaction products was elucidated. To determine the mechanism of binding and activation of heterocyclic substrates in the E. coli PNP active site, molecular modeling of the fleximer base and reaction products in the enzyme active site was carried out. As for N1-pyridinium riboside, there are two possible locations for it in the PNP active site. The presence of a relatively large space in the area of amino acid residues Phe159, Val178, and Asp204 allows the ribose residue to fit into that space, and the heterocyclic base can occupy a position that is suitable for subsequent glycosylation. Perhaps it is this "upside down" arrangement that promotes secondary glycosylation and the formation of minor bis-riboside products.

Covalency parameters for nine-coordinated thorium acylpyrazolone complexes along with their synthesis and crystal features

This study discusses the synthesis and characterization of three thorium complexes with a general composition of [Th(L)4(EtOH)] demonstrated a nine-coordinated geometry in acylpyrazolone chemistry, a novel finding supported by single crystal evidence. A detailed analysis of complex [Th(L2)2(DMF)] was conducted, utilizing single-crystal X-ray diffraction data and Hirshfeld surface area analysis to investigate secondary interactions, exploring the planarity and bonding characteristics of the crystals. Covalency parameters such as the Nephelauxetic ratio, Sinha parameter, bonding parameter, and angular overlap parameter were calculated from electronic spectral data, revealing positive covalency and electron delocalization across the 5f orbital for all complexes. Notably, the presence of solvent bound to the 9th coordination site of the complex suggests potential changes in covalency across different solvents, thereby indirectly impacting chemical characteristics.

Synthesis and Conformational Features of Luminescent Phosphoguanidine with a Phenylbenzothiazole Substituent

Synthesis and Conformational Features of Luminescent Phosphoguanidine with a Phenylbenzothiazole Substituent

Fundamentals of Quantum Dots and Features of Microwave Solvothermal Synthesis

Fundamentals of Quantum Dots and Features of Microwave Solvothermal Synthesis

Extrastrong aggregates of detonation nanodiamonds: structure and formation

Commercially available powders of detonation nanodiamond (DND) contain extrastrong 20–120 nm sized aggregates, in an amount sometimes up to 50% by mass sustainable to the conventional methods of deaggregation. It demonstrates the significant inhomogeneity structure of products of detonation synthesis and noticeably reduces the yield of 4.0 − 5.0 nm individual isolated particles obtained from DNDs. The presence of these aggregates is obviously related to the some essential features of detonation synthesis. This work presents the results of studying such extrastrong aggregates from DND powder. In order to determine the structure we applied the heat treatment of samples in vacuum and in air, and the subsequent study using Raman spectroscopy, X-ray diffraction, UV–vis spectroscopy, analysis of specific surface and dynamic light scattering (DLS). As a result, a structural model of extrastrong aggregates is proposed. It is shown that extrastrong aggregates consist notably of relatively large (∼8.0 nm) single crystalline diamond particles bonded by facets and covered by smaller 4.5 − 3.0 nm and less crystalline grains. Our results add the details for description of formation processes of diamond particles and aggregates in detonation synthesis from excessive carbon in the composition of explosives.

C-H Functionalization-Enabled 11-Step Semisynthesis of (-)-Veragranine A and Characterization of Synthetic Analogs in Osteoarthritis-related Pain Treatment.

We report an efficient semisynthesis of the cholestane steroidal alkaloid (-)-veragranine A with a 6/6/6/5/6/6 hexacyclic ring system, eight stereocenters, and a unique C12-C23 linkage. Our synthesis features a Schönecker-Baran C-H oxidation at C12, a Suzuki-Miyaura cross-coupling to form the C12-C23 bond, and a hydrogen atom transfer (HAT)-initiated Minisci C-H cyclization to forge the C20-C22 bond with desired stereochemistry at C20. These enabling transformations significantly enhanced the overall synthetic efficiency and delivered (-)-veragranine A in 11 steps and over 200 mg from cheap and readily available dehydroepiandrosterone. In addition, this approach allowed flexible syntheses of novel synthetic analogs for biological evaluations in sensory neurons in vitro and in an in vivo model of arthritic pain, from which two novel lead compounds were identified for further development.

Features of Synthesis of Graft Copolymers of Chitosan and Acrylic Acid

Features of Synthesis of Graft Copolymers of Chitosan and Acrylic Acid

FPGA Based Accelerator for Implementation of Large Integer Polynomials

A 13-bit multiplier is implemented on the Artix- 7 100T FPGA using a divide-and-conquer algorithm. The designis coded in SystemVerilog, leveraging its powerful features for hardware description and synthesis. The divide-and-conquer approach breaks down the multiplication task into smaller sub- tasks, enhancing efficiency and reducing complexity. The FPGA’s high- performance capabilities, particularly on the Artix-7 100T board, make it well-suited for accelerating the computations involved. Additionally, Area Delay Product (ADP) tools are employed to evaluate the algorithm’s efficiency. This project aims to showcase the synergy between algorithmic design, hardware implementation, and FPGA capabilities, emphasizing the versa- tility of the Artix-7 100T FPGA in handling complex arithmetic operations.

Features of Few-Layer Phosphorene Structure Synthesis by Plasma-Assisted Electrochemical Exfoliation of Black Phosphorus

Features of Few-Layer Phosphorene Structure Synthesis by Plasma-Assisted Electrochemical Exfoliation of Black Phosphorus