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In this paper, an ionic liquid-based aqueous two-phase system (ILATPS) was applied to the chiral separation of α-cyclohexylmandelic acid (α-CHMA) enantiomers with hydroxypropyl-β-cyclodextrin (HP-β-CD) as the chiral selector. Several influencing parameters were investigated including the types and concentration of ionic liquids, the amount of phase-forming salt, temperature, mixing time, pH, and the content of HP-β-CD. The results showed that not all ILATPS had the ability to chirally recognise the selected enantiomers and that [C4mim]BF4/(NH4)2SO4-based ATPS possessed the best enantioseparation ability of the investigated ILATPSs. Under optimal conditions, the separation factor (α) attained 1.59 in a single-step extraction. ILATPS is much “greener” than other liquid-liquid extraction systems, showing its potential for application to the chiral separation.

An alcohol/salt-based aqueous two-phase system (ATPS) was employed for enantioseparation of (R,S)-mandelic acid (MA) and (R,S)-α-cyclohexylmandelic acid (α-CHMA). Sulfonated β-cyclodextrin (Sf-β-CD) with different degrees of substitution (DS) was considered as the chiral selector. The ethanol/(NH4)2SO4 system showed the optimal chiral recognition ability for MA. To optimize the experimental conditions, Sf-β-CD concentration, ethanol and salt concentration, temperature, and pH were studied. The recognition ability of enantiomers was mainly dependent on the type of the chiral selector but the ethanol and (NH4)2SO4 concentrations also had significant influence on the enantiomeric recognition. The maximum values of α and ee up of 1.69 and 16.3 % were obtained, respectively, for MA under the optimal conditions. A potential application of this alcohol/salt ATPS is the scale-up of chiral separation of MA.

In the title compound, C8H7BrO3, an intra­molecular hydrogen bond exists between the hydroxyl group and the O atom of the carbonyl group. The mol­ecules are stacked along the b axis with weak π–π inter­actions.

The molecule of the title compound, C11H12N2O6, is essentially planar except for the alkyl chain, which has a non-extended conformation.

In the title compound, C10H11NO5, all bond lengths and angles show normal values. Weak inter­molecular O—H⋯O hydrogen bonds form centrosymmetric dimers, which are further linked by π–π inter­actions into ladders extending along the a axis.

In the title compound, C7H13NO4, there are two independent mol­ecules in the asymmetric unit. All bond lengths and angles in the mol­ecules are in normal ranges. The ψ1 and ψ2 torsion angles are 159.9 (4) and −23.4 (5)°, respectively, in the first molecule, and the ψ3 and ψ4 torsion angles 157.7 (4) and −26.7 (5)°, respectively, in the second. Each of the independent mol­ecules has a different comformation. The translationally and screw-related mol­ecules are connected by N—H⋯O hydrogen bonds, forming a two-dimensional network parallel to the ac plane.