Adsorption behavior of a solute is one of the most important factors to consider when designing a batch and a continuous liquid chromatographic separation process. In liquid chromatography, this ...behavior is based on the adsorption equilibrium between the liquid mobile-phase and solid stationary-phase. However, most retention models have been developed under a linear adsorption isotherm: very few researchers have investigated the relationship between the adsorption parameters and the mobile phase composition, and some empirical models have been introduced. In this work, adsorption isotherms were obtained by a frontal analysis for three small molecular compounds (benzene, toluene, and chlorobenzene) on a commercial C
18
bonded silica column. The absorption based on the Langmuir, Freundlich, and Langmuir-Freundlich models were investigated according to changes of the composition of methanol highly enriched eluent. The calculations and analysis of the coefficients obtained for the three models confirm that the adsorption data for solutes are best modeled with the Langmuir-Freundlich isotherm. In spite of the acceptable accuracy, Langmuir and Freundlich isotherm models couldn’t satisfactorily describe the mechanism and provide objective information on the physical nature of the absorption.
Total Synthesis of (−)-Conolutinine Feng, Xiangyang; Jiang, Guangde; Xia, Zilei ...
Organic letters,
09/2015, Letnik:
17, Številka:
18
Journal Article
Recenzirano
The first enantioselective synthesis of (−)-conolutinine was achieved in 10 steps. The synthesis featured a catalytic asymmetric bromocyclization of tryptamine to forge the tricycle intermediate. ...Hydration of an alkene catalyzed by Co(acac)2 was also employed as a key step to diastereoselectively introduce the tertiary alcohol moiety. The absolute configuration of (−)-conolutinine was established to be (2S,5aS,8aS,13aR) based on this asymmetric total synthesis.
Methods to rapidly detect and differentiate chiral N-heterocyclic compounds become increasingly important owing to the widespread application of N-heterocycles in drug discovery and materials ...science. We herein report a 19F NMR-based chemosensing approach for the prompt enantioanalysis of various N-heterocycles, where the dynamic binding between the analytes and a chiral 19F-labeled palladium probe create characteristic 19F NMR signals assignable to each enantiomer. The open binding site of the probe allows the effective recognition of bulky analytes that are otherwise difficult to detect. The chirality center distal to the binding site is found sufficient for the probe to discriminate the stereoconfiguration of the analyte. The utility of the method in the screening of reaction conditions for the asymmetric synthesis of lansoprazole is demonstrated.
Direct deoxyazidation of alcohols with NaN
is a straightforward method for the synthesis of widely used alkyl azides in organic chemistry. However, known methods have some limitations such as high ...reaction temperatures and narrow substrate scope. Herein, a general and practical method for the preparation of alkyl azides from alcohols using NaN
has been developed. N-tosyl-4-chlorobenzenesulfonimidoyl fluoride (SulfoxFluor) plays an important role in this deoxyazidation process, which converts a broad range of alcohols into alkyl azides at room temperature. The power of this deoxyazidation protocol has been demonstrated by successful late-stage deoxyazidation of natural products and pharmaceutically relevant molecules.
The first direct access to unprotected amino-pyrroloindoline via aminocyclization of tryptamine and tryptophan has been described. A variety of structurally diverse amino-pyrroloindolines are ...furnished by the use of O-(2,4-dinitrophenyl)hydroxylamine (DPH) as the nitrogen source in the presence of catalytic Rh2(esp)2.
In the present work, a reversed phase high performance liquid chromatographic method (HPLC) has been developed and validated for analysis of matrine and oxymatrine in Sophora Flavescens Ait. HPLC ...separation of the alkaloids was performed on a C
18
column. A mobile phase composed of methanol-water-trifluoroacetic in a ratio of 16:84:0.002 (v/v) was found to be the most suitable mobile phase for this separation. The extracted amounts are 0.0091 and 0.15 mg/g and the relative standard deviations were 3.3% for the matrine and 2.9% for the oxymatrine analysis.
Abstract
With the continuous development of exploration technology, the magnitude of seismic data is getting larger and larger, and the access efficiency of seismic data has become the main ...bottleneck in the process of seismic data processing. The cluster structure realizes the separation of computing and storage. The data is stored in the disk array, and the data is calculated in the computing node. The maximum network speed between each computing node and the management node is 1GB/s, and the total maximum network speed of all computing nodes is 5GB/S (peak value). In addition, for disk array, the maximum read speed can be ignored (more than 1GB/s) without considering the network bandwidth, while the maximum write speed is 350MB/s. In the process of data processing, it needs to flow between the disk array and the computing node, and its speed must be affected by the network bandwidth. Therefore, the theoretical maximum I/O speed of the system is 1GB/s for reading and 350MB/s for writing. To build a multi format seismic data model, the loading of the system before optimization can not support the original seismic data format, so the original seismic data (such as SEGY and SEGD) needs to be converted into the internal ATT format of the system. In this process, the whole original data needs to be read circularly, and the new file is written circularly, and then the new file is decompiled, Save the header part into the table in the database. Export is the opposite process, which needs to convert ATT format to SEGY or SEGD format.
Abkürzung: Eine enantioselektive Bromcyclisierung von Tryptamin unter Verwendung eines anionischen chiralen Phasentransferkatalysators führt direkt zu chiralen 3‐Brompyrroloindolinen. Die Reaktion ...ermöglicht eine vierstufige enantioselektive Synthese von (−)‐Chimonanthin. PG=Schutzgruppe.
In search of novel anti-ischemic stroke agents with higher potency than a known drug 3-n-butylphthalide (NBP), a series of hybrids ((S)- and (R)-5a–f) from optically active ring-opened NBP derivative ...and isosorbide were synthesized for evaluating their anti-ischemic stroke activity. Compound (S)-5e displayed the strongest activity in inhibiting the adenosine diphosphate (ADP) and arachidonic acid (AA)-induced platelet aggregation in vitro, with 10.0- and 8.4-fold more effectiveness than (S)-NBP, respectively. Furthermore, (S)-5e was stable in artificial gastrointestinal fluids and could penetrate the blood–brain barrier (BBB) with an appreciate lipid/water partition coefficient relative to (S)-NBP. More importantly, oral treatment with (S)-5e protected from acute thrombosis and inhibited the ischemia/reperfusion-related brain injury in animals. Our findings suggest that (S)-5e may be promising for further evaluation for the intervention of ischemic stroke.
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