Enantioseparation of Phenylsuccinic Acid Enantiomers by Solvent Sublation with Collaborative Selectors

Abstract

A new solvent sublation (SS) system for chiral separation is introduced by using phenylsuccinic acid (H2A) as the model enantiomers. The experiments were carried out in a traditional SS apparatus but with collaborative chiral selectors: dibenzoyl-L-tartaric acid (L-DBTA) in the organic phase and hydroxypropyl-β-cyclodextrin (HP-β-CD) in the aqueous phase. The chiral recognition abilities of the two selectors are opposite for the H2A enantiomers. Several important parameters were investigated. The results demonstrate that enantioselective sublation and partitioning behavior are mainly dependent on the pH of the solution, the concentrations of chiral selectors and H2A. Furthermore, the flow rate of air and flotation time also have some effects on the enantioseparation. Under the optimized conditions, the enantioselectivity expressed by the separation factor (β) and enantiomer excess (e.e.%) are 2.47 and 29.50%, and the yields of R-H2A and S-H2A are 0.23 and 0.13 g·L−1, respectively. Compared with the SS system with the single selector HP-β-CD in the aqueous phase (or L-DBTA in the organic phase), the increased values of β and e.e.% in the new SS system with collaborative selectors are 1.31 (or 1.38) and 5.90% (or 13.82%), respectively.