Separation Of Racemic Compounds Research Articles

Chiral Nanochannels of Ordered Mesoporous Silica Constructed by a Pillar[5]arene-Based Host-Guest System.

The separation of racemic compounds by chiral nanochannels has attracted extensive attention. However, the fabrication of high-performance chiral nanochannels is still a challenge owing to the difficulty in magnifying the weak chiral interaction to macroscopic properties of materials. Herein, by introducing a l-alanine-pillar[5]arene host to achiral ordered mesoporous silica (OMS), chiral OMS nanochannels were fabricated, which exhibited excellent selectivity (ee value up to 90.2%) to separate racemic drugs with promising reusability and stability. Besides, it was identified that enantioselective separation took place through a molecular-recognition-adsorbed transport mechanism. This work highlights the great potential of chiral OMS nanochannels as a platform for enantioselective separation.

Separation of racemic compound by nanofibrous composite membranes with chiral selector

A series of unique composite membranes formed from a nanoµ fibrous material with different amounts of a chiral selector was used for separation of chiral drugs. The membrane performances were demonstrated through sorption tests, wherein they were soaked in an aqueous solution of racemic D, L-tryptophan (a model chiral drug). The changes in concentration of both enantiomers over time were monitored by HPLC analysis. During 100 days, a blank membrane (without the chiral selector) exhibited no sorption activity. The membranes containing the selector had no influence on the amount of D-enantiomer, while the L-enantiomer was preferentially adsorbed on each membrane. The intensity of the sorption was found to be a direct function of the amount of the selector contained in a particular membrane. The separation of the same model chiral compound was further studied in diffusion cells by pertraction. The preferential sorption of L-tryptophan in the feed underlined the crucial importance of the selector in an active layer in view of chiral recognition of enantiomers. Due to the exclusive membrane material, the retention of L-tryptophan in the membrane materials did not block the passage of D-enantiomer into the permeate at any point during the experiment. Moreover, the nanomaterial in the active layer assured the distribution of the selector to the point that only 50% of (S, S)-1,2-diaminocyclohexane in one part of the active layer was sufficient to achieve 99% of enantioselectivity. The membranes – fresh and used – were analysed by Fourier-transform infrared (FTIR) spectroscopy and characterized by scanning electron microscopy (SEM) confirming the stability of the tested membranes. To complete the study, the role of the polyamide active layer in chiral recognition of tryptophan enantiomers was proposed.

Drug Stereochemistry: A Prodigy For Pharmacology and Drug Development.

Stereochemistry has evinced the importance of many chiral drugs with respect to drug designing and development. A literature review was conducted for several chiral drugs involving pharmacokinetic and pharmacodynamic parameters of their enantiomers along with their uses in certain diseased conditions. This article mainly includes the pharmacological profile review of some chiral drugs and the aspects due to which the single enantiomer is of importance as compared to the racemic mixture of the drug. This was achieved by moderating the side effects or toxic effects; or by the potentiated activity of the single enantiomer. Resolution deals with the separation of racemic compounds which shows up the credibility to obtain the desired enantiomeric properties. As isomers vary in their pharmacokinetic and pharmacodynamic profiles, chiral drugs have showcased considerable importance in the drug development process. Both the enantiomers have a different pharmacological profile in the treatment of a disease, which differentiates them from drug racemates.

Covalent Organic Frameworks with Chirality Enriched by Biomolecules for Efficient Chiral Separation.

The separation of racemic compounds is important in many fields, such as pharmacology and biology. Taking advantage of the intrinsically strong chiral environment and specific interactions featured by biomolecules, here we contribute a general strategy is developed to enrich chirality into covalent organic frameworks (COFs) by covalently immobilizing a series of biomolecules (amino acids, peptides, enzymes) into achiral COFs. Inheriting the strong chirality and specific interactions from the immobilized biomolecules, the afforded biomolecules⊂COFs serve as versatile and highly efficient chiral stationary phases towards various racemates in both normal and reverse phase of high-performance liquid chromatography (HPLC). The different interactions between enzyme secondary structure and racemates were revealed by surface-enhanced Raman scattering studies, accounting for the observed chiral separation capacity of enzymes⊂COFs.

Covalent Organic Frameworks with Chirality Enriched by Biomolecules for Efficient Chiral Separation

AbstractThe separation of racemic compounds is important in many fields, such as pharmacology and biology. Taking advantage of the intrinsically strong chiral environment and specific interactions featured by biomolecules, here we contribute a general strategy is developed to enrich chirality into covalent organic frameworks (COFs) by covalently immobilizing a series of biomolecules (amino acids, peptides, enzymes) into achiral COFs. Inheriting the strong chirality and specific interactions from the immobilized biomolecules, the afforded biomolecules⊂COFs serve as versatile and highly efficient chiral stationary phases towards various racemates in both normal and reverse phase of high‐performance liquid chromatography (HPLC). The different interactions between enzyme secondary structure and racemates were revealed by surface‐enhanced Raman scattering studies, accounting for the observed chiral separation capacity of enzymes⊂COFs.

Development and validation of HPLC method for the resolution of derivatives of 1-bromo-3-chloro-2-propanol: a novel chiral building block for the synthesis of pharmaceutically important compounds

The methods for the separation of racemic compounds [(RS)-1-bromo-3-chloro-2-propanol, (RS)-1-bromo-3-chloropropan-2-yl acetate] into the corresponding enantiomers were tried to develop in high performance liquid chromatography in a single injection mode. In the case of HPLC, both the reversed (Phenomenex Lux 5u cellulose-1, Lux 5u cellulose-2, Lux 5u amylose-1) and normal phase (Chiralcel OJH, ODH, ADH) chiral columns were used for this purpose. HPLC methods could not resolute the desired enantiomers. However, phenoxy derivatives of (RS)-1-bromo-3-chloro-2-propanol and (RS)-1-bromo-3-chloro- propan-2-yl acetate were separated by normal phase (ODH) column using a mobile phase consisting of n-hexane and isopropanol (80: 20) at a flow rate of 0.5 mL/min (25°C) and detected at 254 nm. The method was validated for linearity, range, accuracy and precision. The developed method was applied for monitoring the progress of lipase catalyzed enantioselective synthesis of (S)-1-bromo-3-chloropropan-2-yl acetate from (RS)-1-bromo-3-chloro-2-propanol. All the analytes were synthesized chemically.

Synthesis of chiral mesoporous silica and its potential application to asymmetric separation

Chiral mesoporous silica (CMS) has been successfully synthesized in the presence of basic amino acids; the use of basic amino acids in combination with the chiral anionic surfactant is advantageous for the formation of CMS in terms of uniformity in the twisted morphology. We first demonstrate that thus obtained chiral mesoporous silicas can be used for the enantioselective separation of racemic compounds; the helical rod-shaped CMS is found to be capable of asymmetric separation of racemic N-trifluoroacetylalanine ethyl ester (CF3CO-Ala-OEt). The left handedness-rich CMS shows asymmetric preferential adsorption of the L isomer and vice versa.

Separation of racemic compounds on amylose and cellulose dimethylphenylcarbamate‐coated zirconia in HPLC

AbstractZirconia particles are a very robust material and have received considerable attention as a stationary phase support for HPLC. Chromatographic performances of ADMPC‐ and CDMPC‐coated zirconia as chiral stationary phases (CSPs) were compared by measuring the chiral discrimination of a set of 14 racemic compounds on the two columns. On the whole CDMPC‐zirconia showed better chiral selectivity for the test compounds than ADMPC‐zirconia. The two CSPs show complementary chiral recognition capability for the types of racemates studied. Chiral selectivities of ADMPC‐ and CDMPC‐coated zirconia were also compared with those of ADMPC‐ and CDMPC‐coated silica. The zirconia CSPs exhibited comparable and sometimes better enantioselectivity than the corresponding silica CSPs.