Chiral ligand exchange countercurrent chromatography: Equilibrium model study on enantioseparation of mandelic acid

Enantioseparation of 3‐phenyllactic acid by chiral ligand exchange countercurrent chromatography

“…To select a biphasic solvent system along with a suitable chiral selector with high enantiorecognition was the important step as for a successful enantioseparation by countercurrent chromatography, in which the chiral selector should be dissolved in only one phase of two‐phase solvent systems. In our previous work, a biphasic solvent system composed of hexane/ n ‐butanol/water with different volume ratio was selected for enantioseparation of mandelic acid derivatives when N ‐ n ‐dodecyl‐ l ‐proline was used as the chiral ligand with Cu 2+ as the transitional metal ion . With the optimized separation conditions, it was found that no successful enantioseparation of 3‐phenyllactic acid could be achieved when the same chiral ligand N ‐ n ‐dodecyl‐ l ‐proline was used because the enantioseparation factor was found to be <1.10.…”

“…Two chiral ligands were synthesized: N ‐ n ‐dodecyl‐ l ‐proline and N ‐ n ‐dodecyl‐ l ‐hydroxyproline. (i) N ‐ n ‐dodecyl‐ l ‐proline was synthesized by a one‐step reductive N‐alkylation of the amino acid and purified with silica gel column chromatography, as described in our previous work . (ii) N ‐ n ‐dodecyl‐ l ‐hydroxyproline was prepared as the followings: n ‐dodecyl aldehyde (0.11 mol) was dissolved in 150 mL of methanol.…”

“…However, it is always necessary to modify the chemical structure of chiral ligand used in countercurrent chromatography to constrain its solubility in only one of the two phases. Enantioseparation of series of mandelic acid derivatives by countercurrent chromatography with N ‐ n ‐dodecyl‐ l ‐proline as chiral ligand was investigated and separation mechanism was proposed in our previous work . In our following studies, it was found that no successful enantioseparation of some tested racemic 2‐hydroxylcarboxylic acids by countercurrent chromatography could be obtained when the same chiral ligand N ‐ n ‐dodecyl‐ l ‐proline was used.…”

“…Recently, increasing number of papers has been published about enantioseparations by countercurrent chromatography . Chiral ligand exchange countercurrent chromatography was derived from the traditional chiral ligand exchange chromatographic techniques, in which a stereospecific ternary complex formed by enantiomer, transitional metal ion, and chiral ligand was also necessary for a successful enantioseparation . However, it is always necessary to modify the chemical structure of chiral ligand used in countercurrent chromatography to constrain its solubility in only one of the two phases.…”

Application of pH‐zone‐refining countercurrent chromatography in the chiral separation of two β‐adrenergic blocking agents

“…Compared with traditional liquid chromatographic techniques, much smaller number of literatures about chiral separation by countercurrent chromatography was available due to its relatively low theoretical plates of separation column [20][21][22][23]. However, in the recent two years, increasing number of papers has been published on preparative enantioseparation by countercurrent chromatography [24][25][26][27][28][29][30][31][32][33]. Unfortunately, only five papers reporting successful chiral separations could be found in the literature when it comes to pH-zone-refining countercurrent chromatography since 1990s [34][35][36][37][38].…”