Synthesis and Evaluation of a Synthetic Polymeric Chiral Stationary Phase for LC Based on the N, N′-[(1R,2R)-1,2-Diphenyl-1,2-Ethanediyl]bis-2-Propenamide Monomer

Gone in seconds: praxis, performance, and peculiarities of ultrafast chiral liquid chromatography with superficially porous particles

A variety of brush-type chiral stationary phases (CSPs) were developed using superficially porous particles (SPPs). Given their high efficiencies and relatively low back pressures, columns containing these particles were particularly advantageous for ultrafast "chiral" separations in the 4-40 s range. Further, they were used in all mobile phase modes and with high flow rates and pressures to separate over 60 pairs of enantiomers. When operating under these conditions, both instrumentation and column packing must be modified or optimized so as not to limit separation performance and quality. Further, frictional heating results in axial thermal gradients of up to 16 °C and radial temperature gradients up to 8 °C, which can produce interesting secondary effects in enantiomeric separations. It is shown that the kinetic behavior of various CSPs can differ from one another as much as they differ from the well-studied C18 reversed phase media. Three additional interesting aspects of this work are (a) the first kinetic evidence of two different chiral recognition mechanisms, (b) a demonstration of increased efficiencies at higher flow rates for specific separations, and

Preparation and evaluation of a new synthetic polymeric chiral stationary phase for HPLC based on the trans-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid bis-4-vinylphenylamide monomer

A new synthetic polymeric chiral stationary phase for liquid chromatography was prepared via free-radical-initiated polymerization of trans-9,10-dihydro-9,10-ethanoanthracene-(11S,12S)-11,12-dicarboxylic acid bis-4-vinylphenylamide. The new polymeric chiral stationary phase (CSP) showed enantioselectivity for many chiral compounds in multiple mobile phases. High stability and sample capacities were observed on this polymeric chiral stationary phase. Mobile phase components and additives affected chiral separation greatly. This new synthetic chiral stationary phase is complementary to two other related commercially available CSPs: the P-CAP and P-CAP-DP columns. Interactions between the chiral stationary phase and analytes that lead to retention and chiral recognition include hydrogen bonding, dipolar, and pi-pi interactions. Repulsive (steric) interactions also contribute to chiral recognition. Figure LC chromatograms showing the analytical (blue) and preparative (red) separations of N-(3,5-dinitrobenzoylleucine) enantiomers on a new synthetic polymeric chiral stationary phase.

HPLC on chiral support with polarimetric detection: Application to conglomerate discovery

In conglomerates, each single crystal contains only one of the two possible enantiomeric forms--either dextrorotatory or levorotatory. The analysis of a single crystal by liquid chromatography on chiral support associated with chiroptical detection is a very efficient tool to reveal the occurrence of a conglomerate. In terms of rapidity and easiness, this method compares favorably with the classical methods used to show this occurrence. Two examples are provided.

Enantiomeric impurities in chiral synthons, catalysts, and auxiliaries. Part 3

The enantiomeric excess of chiral reagents used in asymmetric syntheses directly affects the reaction selectivity and product purity. In this work, 84 of the more recently available chiral compounds were evaluated to determine their actual enantiomeric composition. These compounds are widely used in asymmetric syntheses as chiral synthons, catalysts, and auxiliaries. These include chiral alcohols, amines, amino alcohols, amides, carboxylic acids, epoxides, esters, ketones, and oxolanes among other classes of compounds. All enantiomeric test results were categorized within five purity levels (i.e. <0.01%, 0.01% to 0.1%, 0.1% to 1%, 1% to 10%, and >10%). The majority of the reagents tested were determined to have enantiomeric impurities over 0.01%, and two of them were found to contain enantiomeric impurities exceeding the 10% level. The most effective enantioselective analysis method was a GC approach using a Chiraldex GTA chiral stationary phase (CSP). This method worked exceedingly well with chiral amines and alcohols.