Synthetic Scheme Research Articles

Narrow Near-Infrared Emission from InP QDs Synthesized with Indium(I) Halides and Aminophosphine.

Nonpyrophoric aminophosphines reacted with indium(III) halides in the presence of zinc chloride have emerged as promising phosphorus precursors in the synthesis of colloidal indium phosphide (InP) quantum dots (QDs). Nonetheless, due to the required P/In ratio of 4:1, it remains challenging to prepare large-sized (>5 nm), near-infrared absorbing/emitting InP QDs using this synthetic scheme. Furthermore, the addition of zinc chloride leads to structural disorder and the formation of shallow trap states inducing spectral broadening. To overcome these limitations, we introduce a synthetic approach relying on the use of indium(I) halide, which acts as both the indium source and reducing agent for aminophosphine. The developed zinc-free, single-injection method gives access to tetrahedral InP QDs with an edge length > 10 nm and narrow size distribution. The first excitonic peak is tunable from 450 to 700 nm by changing the indium halide (InI, InBr, InCl). Kinetic studies using phosphorus NMR reveal the coexistence of two reaction pathways, the reduction of transaminated aminophosphine by In(I) and via redox disproportionation. Etching the surface of the obtained InP QDs at room temperature with in situ-generated hydrofluoric acid (HF) leads to strong photoluminescence (PL) emission with a quantum yield approaching 80%. Alternatively, surface passivation of the InP core QDs was achieved by low-temperature (140 °C) ZnS shelling using the monomolecular precursor zinc diethyldithiocarbamate. The obtained InP/ZnS core/shell QDs that emit in a range of 507-728 nm exhibit a small Stokes shift (110-120 meV) and a narrow PL line width (112 meV at 728 nm).

Boosting the convergence of low-variance DSMC by GSIS

The low-variance direct simulation Monte Carlo (LVDSMC) is a powerful method to simulate low-speed rarefied gas flows. However, in the near-continuum flow regime, due to limitations on the time step and spatial cell size, it takes plenty of time to find the steady-state solution. Here we remove these deficiencies by coupling the LVDSMC with the general synthetic iterative scheme (GSIS) which permits the simulation at the hydrodynamic scale rather than the much smaller kinetic scale. As a proof of concept, we propose the stochastic-deterministic coupling method based on the Bhatnagar-Gross-Krook kinetic model. First, macroscopic synthetic equations are derived exactly from the kinetic equation, which not only contain the Navier-Stokes-Fourier constitutive relation, but also encompass the higher-order terms describing the rarefaction effects. Then, the high-order terms are extracted from LVDSMC and fed into synthetic equations to predict the macroscopic properties which are closer to the steady-state solution than LVDSMC. Finally, the state of simulation particles in LVDSMC is updated to reflect the change of macroscopic properties. As a result, the convergence to steady state is greatly accelerated, and the restrictions on cell size and the time step are removed. We conduct the Fourier stability analysis and simulate several canonical rarefied gas flows to demonstrate the advantages of LVDSMC-GSIS: when the Knudsen number is lower than 0.1, it can use the grid size about 10 times larger than that in traditional DSMC, and it can reduce the computational cost by two orders of magnitude in the flow regime.

Simple In Vitro 18O Labeling for Improved Mass Spectrometry-Based Drug Metabolites Identification: Deep Drug Metabolism Study.

The identification of drug metabolites formed with different in vitro systems by HPLC-MS is a standard step in preclinical research. In vitro systems allow modeling of real metabolic pathways of a drug candidate. Despite the emergence of various software and databases, identification of compounds is still a complex task. Measurement of the accurate mass, correlation of chromatographic retention times and fragmentation spectra are often insufficient for identification of compounds especially in the absence of reference materials. Metabolites can "slip under the nose", since it is often not possible to reliably confirm that a signal belongs to a metabolite and not to other compounds in complex systems. Isotope labeling has proved to be a tool that aids in small molecule identification. The introduction of heavy isotopes is done with isotope exchange reactions or with complicated synthetic schemes. Here, we present an approach based on the biocatalytic insertion of oxygen-18 isotope under the action of liver microsomes enzymes in the presence of 18O2. Using the local anesthetic bupivacaine as an example, more than 20 previously unknown metabolites were reliably discovered and annotated in the absence of the reference materials. In combination with high-resolution mass spectrometry and modern methods of mass spectrometric metabolism data processing, we demonstrated the ability of the proposed approach to increase the degree of confidence in interpretating metabolism data.

Synthesis, analysis of mol-ecular and crystal structures, estimation of inter-molecular inter-actions and biological properties of 1-benzyl-6-fluoro-3-[5-(4-methylcyclohexyl)-1,2,4-oxadiazol-3-yl]-7-(piperidin-1-yl)quinolin-4-one.

The title compound, C30H33N4O2F, can be obtained via a two-step synthetic scheme involving 1-benzyl-6-fluoro-4-oxo-7-(piperidin-1-yl)-1,4-di-hydro-quino-line-3-carbo-nitrile as a starting compound that undergoes substitution with hydroxyl-amine and subsequent cyclization with 4-methyl-cyclo-hexane-1-carb-oxy-lic acid. It crystallizes from 2-propanol in the triclinic space group P with a mol-ecule of the title compound and one of 2-propanol in the asymmetric unit. After the mol-ecular structure was clarified using NMR and LC/MS, the mol-ecular and crystalline arrangements were defined with SC-XRD. A Hirshfeld surface analysis was performed for a better understanding of the inter-molecular inter-actions. One strong (O-H⋯O) and three weak [C-H⋯F (intra-molecular) and two C-H⋯O] hydrogen bonds were found. The contributions of short contacts to the Hirshfeld surface were estimated using two-dimensional fingerprint plots showing that O⋯H/H⋯O, C⋯H/H⋯C and C⋯C contacts are the most significant for the title compound and O⋯H for the 2-propanol. The crystal structure appears to have isotropically packed tetra-mers containing two mol-ecules of the title compound and two mol-ecules of 2-propanol as the building unit according to analysis of the distribution of pairwise inter-action energies. A mol-ecular docking study was carried out to evaluate the inter-actions of the title compound with the active centers of macromolecules corresponding to viral targets, namely, anti-hepatitis B activity [HBV, capsid Y132A mutant (VCID 8772) PDB ID: 5E0I] and anti-COVID-19 main protease activity (PDB ID: 6LU7). The data obtained revealed a noticeable affinity towards them that exceeded that of the reference ligands.

Total Synthesis of Leptosperol B through Stereocontrolled Intramolecular 1,4-Addition to Construct the Octahydronaphthalene Framework

Leptosperol B, possessing a unique octahydronaphthalene framework and 5-substituted aromatic ring, was isolated from the leaves of Leptospermum scoparium in 2020. The asymmetric total synthesis of leptosperol B was accomplished in 12 steps from (-)-menthone. The efficient synthetic scheme involves regioselective hydration and stereocontrolled intramolecular 1,4-addition to construct the octahydronaphthalene skeleton, followed by the introduction of the 5-substituted aromatic ring.

Facile and effectual surface modification of polyacrylonitrile (PAN)-based ultrafiltration membranes via manipulating the synergistic interaction of dopamine and enzymes

A drastic improvement in the overall permeability and antifouling performance was observed for the polyacrylonitrile (PAN) ultrafiltration (UF) membrane by the co-incorporation of dopamine (DA), protease (E1), and lipase (E2) in a facile multi-step synthetic scheme. SEM was utilized to indicate the successful formation of modifying layers on the membrane surface, whereas ATR-FTIR and zeta potential were used to provide deeper insight into the membrane surface chemistry. AFM and contact angle were used to assess the membrane's surface roughness and hydrophilicity, respectively. The optimally modified membrane surface was found to be quite hydrophilic, as indicated by the water contact angle value (39.8 ± 0.8°), and water flux across the membrane of 78.09 ± 1.6 kg/m2·h. Simultaneously, natural organic matter (NOM), including milk powder (MP), bovine serum albumin (BSA), and humic acid (HA), were efficiently removed, resulting in 99.9, 92.5, and 80.5 % removal efficiencies, respectively. Notably, the enzyme-immobilized membrane demonstrated outstanding antifouling performance as well as long-term stability. The dynamic anti-NOM fouling studies indicated that the surface modification was potentially capable of overcoming the tradeoff between membrane permeability and selectivity, resulting in FRR values of >90 %. The antibacterial properties of the surface-modified membranes against E. coli and S. aureus were also explored, and the optimal enzyme-immobilized membrane was found to be substantially antibacterial. Overall, this study aims to pave the way for the development of sustainable chemistry in designing innovative and highly efficient membranes.

Facile Synthesis of Key Building Blocks of D18 Series Conjugated Polymers for High-Performance Polymer Solar Cells

D18 and its derivatives (such as D18-Cl) newly emerged as high-performance conjugated polymers for bulk heterojunction (BHJ) solar cells, with efficiency breaching 17% when paired with small molecule acceptors such as Y6 and its derivatives. However, the complex synthesis of D18 series has limited their accessibility to the research community. We redesigned the original synthetic scheme of D18, particularly the key monomer, 5,8-bis(5-bromo-4-(2-butyloctyl)thiophen-2-yl)dithieno[3′,2′:3,4;2″,3″:5,6]benzo[1,2-c][1,2,5]thiadiazole (Br2-T2-DTBT), and replaced a few key steps in the original scheme that were hard to reproduce and/or low yielding with simple to operate and high yielding reactions. Carother’s equation was successfully applied to control/tune the molar mass of D18-Cl, and three representative molar masses (high, medium, and low) of D18-Cl were subject to device testing. It is discovered that a medium molar mass (56 kg/mol) D18-Cl offered the highest performance (average 16.6%) when paired with Y6 as the acceptor in a typical BHJ device configuration, consistent with the literature report. This optimized synthesis of D18 series offers great synthetic tunability, and the modular nature/optimized key reactions will facilitate the design and synthesis of conjugated polymers for optoelectronics.

Constructing time integration with controllable errors for constrained mechanical systems

This paper investigates the numerical features of equivalent Lagrangian formulations for general mechanical systems and gives new insight into the error reduction of the corresponding numerical integrations. To this end, the modified Lagrange’s equations are derived, which give a unified form of equivalent Lagrangian formulations, featuring different generalized constraint forces. By transforming the modified Lagrange’s equations into their discrete versions, the errors of generalized constraint forces are estimated in strong and weak forms. An error analysis is employed to clarify the error generation of different formulations. This helps to identify whether the generalized constraint force contributes considerable errors compared to other terms in the system. Finally, a mechanism of error reduction is explained for the discrete system, providing a way to reduce total errors by adjusting the error generated from the generalized constraint forces. Inspired by this mechanism, a methodology for constructing synthetic integrations is developed. The synthetic integration scheme consists of the main scheme and the counter scheme. In particular, the counter scheme, discretized from the generalized constraint forces, plays an error conditioner that offsets the total error of the integration. Numerical examples demonstrate the significantly higher numerical accuracy and some other possible computational advantages of the proposed method.

The preparation of 2,2′-bithiophene-based conjugated microporous polymers by direct arylation polymerization and their application in fluorescence sensing 2,4-dinitrophenol

In this paper, we report the synthetic strategy of direct arylation polymerization (DAP) for four 2,2′-bithiophene-based conjugated microporous polymers (the 2,2′-BTh-based CMPs) by coupling 2,2′-bithiophene with the building blocks containing bromine. Compared to conventional coupling polymerization, this synthetic scheme is simple, facile and atomically efficient owing to neither preactivating the C–H bonds in 2,2′-bithiophene using organometallic reagents nor synthesis of complex thiophene-based building blocks. The resulting 2,2′-BTh-based CMPs exhibit excellent thermal stability, high specific surface areas, and good microporosity. Their specific surface areas are higher than that of other previously reported CMPs prepared with DAP. The four 2,2′-BTh-based CMPs can be utilized for multicolor fluorescence sensing of 2,4-dinitrophenol (DNP) with the high sensitivity and selectivity. The sensitivities appear to increase with the degree of structural distortion.

SYNTHESIS OF BIOACTIVE POLYHYDROQUINOLINES USING SULFATED TIN OXIDE AS AN EFFICIENT SOLID SUPERACID CATALYST

A novel synthetic scheme has been designed for the synthesis of polyhydroquinoline derivatives via one-pot condensation of aromatic aldehydes, EAA, dimedone, and NH4OAc by employing synthesized STO as a heterogeneous solid acid catalyst in ethanol under reflux condition. FTIR, XRD, and SEM EDX were used to confirm the sulfated tin oxide. BET plots were used to analyze the surface area of the catalyst. The reactions were assessed for diverse solvents and catalyst loading. The yields of all the polyhydroquinoline derivatives were found to range between 80 to 92%. All the synthesized polyhydroquinolines were validated by spectral data. This exercise is efficient and green as it uses an environmentally friendly catalyst, has a significant atom economy, is cost-effective and easy to work up.

An improved total synthesis of tunicamycin V

The tunicamycins are important biochemical tools to study N-linked glycosylation and protein misfolding in cancer biochemistry fields. We reported a convergent synthesis of tunicamycin V with 21% overall yield from D-galactal. We have further optimized our original synthetic scheme by increasing the selectivity of azidonitration of the galactal derivative and developing a one-pot Büchner-Curtius-Schlotterbeck reaction. An improved synthetic scheme reported here enables the synthesis of tunicamycin V in 33% overall yield. In this article, we describe detailed procedures for a gram-scale synthesis of the key intermediate 12 and synthesizing 100 mg of tunicamycin V (1) from commercially available D-galctal-4,5-acetonide. All chemical steps have been repeated multiple times.•Highly selective azidonitration of N-(((3aR,4R,7aR)-2,2-dimethyl-3a,7a-dihydro-4H-[1,3]dioxolo[4,5-c]pyran-4-yl)methyl)acetamide (D-galctal-4,5-acetonide) to form 2-azido-2-deoxy-α/β-D-galactopyranoside derivatives.•Optimized Büchner-Curtius-Schlotterbeck (BCS) reaction procedure for the tunicamycin core structure.•Full detail on the 15-chemical step synthesis of tunicamycin V.

Novel synthetic methodology of Diclofenac derivatives and its spectrochemical studies

To design the novel synthetic scheme, structural modification, characterization, and pharmacological evaluation of new derivatives of Diclofenac drugs is the main aim of the current research work. We describe the utility of novel reagents and green synthetic methodology to formulate the derivatives to enhance its biological action without undesirable effects. Diclofenac sodium is the phenylacetic acid salt and categorized under nonsteroidal anti-inflammatory drug (NSAID) with pain-relieving, antipyretic, and anti-inflammatory activity, but it has limits and adverse effects as gastrointestinal irritation, small intestine damage, nausea, platelet dysfunction and vertigo. Diclofenac amide derivatives are prepared with Sulphanilic acid and Naphthylamine by the following methods such as reflux and microwave irradiation method. Structural modification is carried out to build up the desired properties. The new synthesized derivatives were structurally characterized with the help of FT-IR, UV–Visible spectroscopy, and MS spectrometry techniques. Further we propose the pharmacological evaluation of Diclofenac derivatives will be carried out by in-vivo and invitro methods.

Efficient Synthetic Aperture for Phaseless Fourier Ptychographic Microscopy with Hybrid Coherent and Incoherent Illumination

AbstractFourier ptychographic microscopy (FPM) is a computational high‐throughput technique for high‐resolution and wide field‐of‐view (FOV) imaging applications such as cell biology, medicine screening, and digital pathology. By integrating angle‐varied illumination, iteration phase retrieval, and synthetic aperture, it achieves a significantly enhanced imaging resolution beyond the diffraction limit of the objective lens while retaining its original large FOV without any mechanical movement. However, sufficient data redundancy is a prerequisite for the convergence of the iteration algorithm, which in turn requires dozens or even hundreds of raw images to get a decent resolution, leaving ample room for further improvement. In this paper, an efficient synthetic aperture scheme for FPM is proposed, termed ESA‐FPM. It employs both coherent and incoherent illuminations to maximize the efficiency of data utilization and achieve high spatial‐bandwidth product (SBP) reconstruction with few acquisitions. The data redundancy requirements are further analyzed, suggesting that ESA‐FPM reaches imaging resolution of using only seven images. The experiment with USAF target demonstrates that ESA‐FPM achieves theoretical resolution with only 1.6% of the data of conventional FPM. A customized miniaturized ESA‐FPM system with a high‐numerical‐aperture, low‐magnification objective lens, and a high‐brightness LED array is built, demonstrating its potential for biomedical and pathological applications.

Studies Towards the Total Synthesis of Populusone: Stereoselective Construction of Functionalized 2-Oxa-bicyclo[2.2.2]octenes

AbstractA short and efficient synthetic access to functionalized compounds displaying major structural elements of the natural product populusone is elaborated by exploiting a diastereoselective Mukaiyama aldol addition followed by a triflic anhydride-induced oxa-Michael addition to construct the sensitive 2-oxa-bicyclo[2.2.2]octene unit as an enol triflate, which is directly used in a subsequent Suzuki cross-coupling. While attempts to close the strained 10-membered ring by means of Ru-catalyzed ring-closing metathesis were not successful, the developed synthetic scheme opens a rapid synthetic access to advanced intermediates, which may allow the completion of the total synthesis of populusone in the future.

Synthetic Sensorless Control Scheme for Full-Speed Range of Switched Reluctance Machine Drives With Fault-Tolerant Capability

In this article, a synthetic sensorless control scheme for full-speed range of switched reluctance machine (SRM) drives with phase absence fault-tolerant capability is proposed, which integrates the phase inductance gradient detection and the idle phase inductance threshold comparison. First, in each excitation period, only the demagnetization inductance slope negative-going zero-crossing detection (D-ISNZ) is performed to avoid the erroneous aligned position estimation in the main excitation region. Then, considering the sensitivity of the D-ISNZ method to demagnetization regions, the remedial sensorless control strategy based on single inductance threshold (SIT) is adopted. Also, the synthetic algorithm is developed for the seamless combination between the two sensorless methods. To enhance the reliability of sensorless operation, a fault-tolerant rotor position estimation method considering speed transient and phase deviation compensation is also presented. Furthermore, to ensure stable sensorless starting, a commutation instant direct estimation method based on online determined double inductance thresholds is developed. The proposed sensorless control scheme can achieve robustness operation under various working conditions without any prior knowledge of magnetic characteristics, large storage memory occupations, and intensive computations. Experiments are conducted on a three-phase 12/8 SRM experimental setup to verify the feasibility of the proposed sensorless control scheme.

A Simple and Highly Selective Colorimetric Sensing of Hg2+ Ions Based on Anti-Aggregation of Gold Nanoparticles

In this work, a highly sensitive and selective colorimetric sensor assay for the detection of Hg2+ ions is presented utilizing an anti-aggregation sensing approach with AuNPs and an amine-based sensor (S). The addition of sensor (S) to gold nanoparticles (AuNPs) leads to their aggregation and, thus, color variation from red to blue. Whereas, in the presence of Hg2+ ions, i.e., target analyte, sensor (S) preferably binds with Hg2+ ions over AuNPs, thus inhibiting their aggregation and subsequent color change. This approach is optimized in terms of various analytical parameters, such as incubation time, pH effect, and S titration, to obtain high sensitivity and selectivity. The UV–Visible studies validate the performance of developed approach for Hg2+ ions detection, and the limit of detection was calculated to be 17 nM, which is lesser than its permissible limit (30 nM) in drinking water. The interference studies also confirm the develop approach selectivity for Hg2+ ions even in the presence of coexisting ions in aqueous media. The experimental results were further correlated with the computational density functional theory (DFT) studies. The presented method is not only cost-effective but also eliminates tedious synthetic schemes and need of laborious manpower.

Convergent Assembly of the Tricyclic Labdane Core Enables Synthesis of Diverse Forskolin‐like Molecules

AbstractWe report a new synthetic strategy for the flexible preparation of forskolin‐like molecules. The approach is different from the previously published works and employs a convergent assembly of the tricyclic labdane‐type core from pre‐functionalized cyclic building blocks. Stereoselective Michael addition enabled the fragment coupling with excellent control over three newly created contiguous stereocenters, all‐carbon quaternary centers included. Silyl enol ether‐promoted ring‐opening metathesis paired with ring closure were the other key steps enabling concise assembly of the tricyclic core. Late‐stage functionalization sequences transformed the tricyclic intermediates into a set of different forskolin‐like molecules. The modular nature of the synthetic scheme described herein has the potential to become a general platform for the preparation of analogs of forskolin and other complex tricyclic labdanes.

Convergent Assembly of the Tricyclic Labdane Core Enables Synthesis of Diverse Forskolin-like Molecules.

We report a new synthetic strategy for the flexible preparation of forskolin-like molecules. The approach is different from the previously published works and employs a convergent assembly of the tricyclic labdane-type core from pre-functionalized cyclic building blocks. Stereoselective Michael addition enabled the fragment coupling with excellent control over three newly created contiguous stereocenters, all-carbon quaternary centers included. Silyl enol ether-promoted ring-opening metathesis paired with ring closure were the other key steps enabling concise assembly of the tricyclic core. Late-stage functionalization sequences transformed the tricyclic intermediates into a set of different forskolin-like molecules. The modular nature of the synthetic scheme described herein has the potential to become a general platform for the preparation of analogs of forskolin and other complex tricyclic labdanes.

The tris[4-(2-thienyl)phenyl]amine-based conjugated microporous polymers synthesized via direct arylation polymerization for fluorescence-sensing iodine and nitrophenols

A new series of TPATTh-based CMPs have been synthesized via a readily synthetic scheme of C–H direct arylation polymerization (DAP) that involves thiophene-flanked arenes, tris[4-(2-thienyl)phenyl]amine (TPATTh) and commercially available multi-brominated aryls, (2,2′,7,7′-tetrabromo-9,9′-spirobifluorene (TBrSBF), 1,3,6,8-tetrabromopyrene (TBrPy), 2,5-dibromopyrazine (DBrPy), and 1,6-dibromopyrene(DBrPz)). Preactivation of the C–H bonds in the aromatic monomers is not required. The resulting TPATTh-based CMPs display good thermal stability. The porosities of the TPATTh-based CMPs are lain on the structures of the multi-brominated aryls. The TPATTh-based CMPs present good fluorescence emission performances either in the solid states or dispersed in the solvents, and show different colors under 365 ​nm fluorescence irradiation. The resulting TPATTh-based CMPs were used to fluorescence sense to I2, PA, DNP, and o-NP with high Stern-Volmer quenching constants (Ksv).

A new synthetic feature generation scheme based on artificial immune systems for robust offline signature verification

Identity verification based on offline handwritten signatures is required in various financial and administrative domains using paper documents. Commonly, the performance of signature verification systems is altered by the lack of sufficient authentic signatures. To overcome such shortcoming, various data augmentation schemes were proposed to generate synthetic samples. Since both genuine and synthetic signatures undergo a feature generation process inside the verification system, we propose to directly apply data augmentation on features instead of the signature image. Such an approach can give more pertinent synthetic features, than those derived from synthetic signatures. The proposed features generator is based on mutation, cloning, and resources competition mechanisms of artificial immune systems. It is evaluated on two descriptors by using SVM classifier in the verification step. As a first descriptor, we introduce the multi-oriented local difference features. The second descriptor is the histogram of templates which is used for comparison aims, since it showed satisfactory performance for handwritten signature characterization. Experiments conducted on CEDAR, GPDS-300, and MCYT-75 datasets, highlight the effectiveness of synthetic features, which allow at least an improvement of 8% when the verification system is developed by using one real signature. Also, the proposed MLDF outperforms both HOT and several state of the art features including LBP and SigNet.