Enantioselective liquid-solid extraction for screening of structurally related chiral stationary phases

Abstract

SummaryAn enantioselective liquid-solid batch extraction method is described for the screening of novel chiral stationary phases (CSPs) during optimization studies of chiral selectors derived form a common lead structure. Extraction enantioselectivity (a) values can be calculated from the enantiomeric excess ee-values of the selectand, which are measured in the liquid phase by enantioselective HPLC. Extraction e-values have been correlated with chromatographic e-values. The influence was studied of several experimental parameters of the assay (pHa, buffer concentration, temperature, selector/selectand and phase ratio) on the enantiomeric excess (ee) values of the selectands and the enantioselectivity of the CSPs, respectively. The derived statistically significant model has then been implemented to predict chromatographic 0c-values of novel CSPs. For example, an ee of 89.3 % for DNB-Leu as selectand could be achieved in batch extraction for a novel synthesized but mechanistically similarly-acting CSP derived form quinine. This corresponds to a calculated extraction e-value of 17.7. Based Oil this eextraction a chromatographic e-value of 28.8 was predicted by the linear correlation model; the experimental HPLC e-value of 31.7 was in good agreement and demonstrated the validity of the proposed screening method. The method is particularly helpful in SO optimization studies.

Enantioselective sorption of the chiral fungicide metalaxyl on soil from non-racemic aqueous solutions: Environmental implications

“…Even working with pure chiral sorbents, the enantioselective sorption of chiral compounds can be difficult to observe under batch conditions [19], and the heterogeneity and complexity of organomineral soil colloids make the identification of sorption enantioselectivity even more complicated [20,21]. Thus, questions remain as to whether soil components assemblages are net "isomer-blind" at the macro-scale in their sorption of chiral compounds or whether chiral constituents, e.g.…”

Simultaneous microbatch screening of enantiorecognition on solid chiral selectors using selected mixtures of test‐racemates: a case study on cellulose tris(α‐phenylpropionate) with configurational diversity

“…Chiral HPLC of the supernatant allows the determination of the ratio of enantiomers. Welch et al, (1998aWelch et al, ( ,b,1999 and Lindner (Tobler et al, 2000) have described the method in their respective papers. They both addressed the enantioselectivity issues by measuring the ratio of enantiomers in the supernatant.…”

“…The microbatch technology for screening was also recently reported to evaluate several carbamoylated quinine selectors using 50 mg of support in smallscrew-capped test tubes (Tobler et al, 2000). The evaluation was performed with the aid of some racemic derivatized amino acids.…”

Enantiorecognition on solid chiral selectors using microbatch technology: an example of limitation in case of strong association in the racemate

“…In the last few years, we and others have developed microbatch methodologies to evaluate the application field of new chiral selectors or to select commercially available chiral stationary phases (CSPs) (Wolf et al, 1993;Nakano et al, 1998Nakano et al, , 2001Welch et al, 1999Welch et al, , 2001Welch et al, , 2002Roussel et al, 2000Roussel et al, , 2001Bluhm et al, 2000;Tobler et al, 2000;Wang et al, 2000;Xu et al, 2001). The so-called microbatch method for the evaluation of solid chiral selectors as potential CSP involves the enantioselective partition of a racemate between the solid chiral support and an achiral solvent.…”