scholarly journals New Discoveries in Enantiomeric Separation of Racemic Tofisopam

2019 ◽  
Vol 2019 ◽  
pp. 1-10
Author(s):  
Miklós Hunor Bosits ◽  
Emese Pálovics ◽  
János Madarász ◽  
Elemér Fogassy
Keyword(s):  
Efficient Solution ◽  
Enantiomeric Separation ◽  
Solvent Mixture ◽  
Enantiomeric Purity ◽  
Thermodynamic Control ◽  
Resolution Process ◽  
Diastereomeric Excess

Resolution process of tofisopam has been re-evaluated now based on our new investigations. Originally, it was carried out in the water-chloroform system, where the intermediate salt of high diastereomeric excess was described as (R)-TOF·(R,R)-DBTA·(H2O)3. Opposed to previous assumptions, we have actually found that a different solvate composition, (R)-TOF‐(R,R)-DBTA-CHCl3, forms with chloroform, in which molecules of CHCl3 are captured and held with different strengths. Moreover, resolution of TOF with (R,R)-DBTA is possible (and favourable) in water-free solvent and solvent mixture. However, presence of chloroform is essential, and thus, chloroform is also a suitable solvent alone. Among the tested solvents, toluene-chloroform mixture results in the highest resolution efficiency, while the highest enantiomeric purity was achieved when acetonitrile was in the system too. Resolution efficiency can be also increased by using the quasi-racemic resolving agent and thermodynamic control. Purification of enantiomeric mixtures was examined, and recrystallization of the diastereomeric salt was found to be the most efficient solution. Instructive behaviour of the complex enantiomer-conformer system of tofisopam is emphasized.

scholarly journals Development and Validation of a Chiral HPLC Method for Quantitative Analysis of Enantiomeric Escitalopram

2018 ◽  
Vol 16 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Asma Rahman ◽  
Mohammad Rashedul Haque ◽  
M Muhibur Rahman ◽  
Mohammad A Rashid
Keyword(s):  
Pharmaceutical Preparations ◽  
Enantiomeric Separation ◽  
Hplc Method ◽  
Enantiomeric Purity ◽  
Chiral Hplc ◽  
Average Percentage ◽  
Quantitation Limit ◽  
Relative Standard ◽  
Development And Validation

In the present study a rapid, accurate and precise chiral HPLC method was developed and validated for enantiomeric separation of racemate citalopram and escitalopram according to the guidelines of United States of Pharmacopeia (USP) and International Conference on Harmonization (ICH). The chiral chromatographic separation was achieved with ammonium acetate/ ethanol/ 2-propanol/ methylene dichloride (100 : 150 : 70 : 30, v/v) at a flow rate of 0.5 ml/min using a chiral CD-PH column. The HPLC analyses were monitored at 254 nm. The method showed a good linearity with regression coefficient (r2) of 0.998 in the range of 20.0-70.0 μg/ml for escitalopram. The detection limit (LOD), quantitation limit (LOQ) and average percentage of recovery for escitalopram were found to be 2.54, 7.68 μg/ml and 100.28% to 102.86%, respectively. The percentage of relative standard deviation (%RSD) for intra- and inter- day precision were found as 0.16% and 0.09%, respectively. The established method proved as reproducible with a %RSD value of less than 2 and having the robustness within specified limit. The present study also showed the enantiomeric purity or excess (%ee) of seven pharmaceutical preparations of escitalopram. Thus the proposed chiral method can be applied for the enantiomeric purity determination of escitalopram formulations.Dhaka Univ. J. Pharm. Sci. 16(2): 165-172, 2017 (December)

Differential Effects of Prior Experience on the Malware Resolution Process

MIS Quarterly ◽  
2014 ◽  
Vol 38 (3) ◽  
pp. 655-678 ◽  
Author(s):  
Seung Hyun Kim ◽  
◽  
Byung Cho Kim ◽  
◽  
Keyword(s):  
Prior Experience ◽  
Differential Effects ◽  
Resolution Process

Stereodivergent Alkyne Hydrofluorination Using a Simple Practical Reagent

2020 ◽  
Author(s):  
Rui Guo ◽  
Xiaotian Qi ◽  
Hengye Xiang ◽  
Paul Geaneoates ◽  
Ruihan Wang ◽  
...  
Keyword(s):  
Bond Formation ◽  
Biologically Active ◽  
Dft Studies ◽  
Thermodynamic Control ◽  
Important Goal ◽  
Peptide Bonds ◽  
Metal Free ◽  
Vinyl Cation ◽  
E And Z Isomers ◽  
Vinyl Fluorides

Vinyl fluorides play an important role in drug development as they serve as bioisosteres for peptide bonds and are found in a range of biologically active molecules. The discovery of safe, general and practical procedures to prepare vinyl fluorides remains an important goal and challenge for synthetic chemistry. Here we introduce an inexpensive and easily-handled reagent and report simple, scalable, and metal-free protocols for the regioselective and stereodivergent hydrofluorination of alkynes to access both the E and Z isomers of vinyl fluorides. These conditions were suitable for a diverse collection of alkynes, including several highly-functionalized pharmaceutical derivatives. Mechanistic and DFT studies support C–F bond formation through a vinyl cation intermediate, with the (E)- and (Z)-hydrofluorination products forming under kinetic and thermodynamic control, respectively.<br>

Sign in / Sign up

Export Citation Format

Share Document