Chiral recognition and separation of β2-amino acids using non-covalently molecularly imprinted polymers

Non-covalently molecularly imprinted polymers (MIPs) for β2-amino acids were prepared for the first time. N-(2-chlorobenzyloxycarbonyl)-(R)-β2-homophenylalanine (N-2-ClZ-(R)-β2-HPhe) was imprinted with methacrylic acid (MAA) and/or 4-vinylpyridine (4-VPy) as the functional monomers, with ethylene glycol dimethacrylate (EDMA) as the cross-linker. The MIPs made with different ratios of MAA ∶ 4-VPy were studied in HPLC mode. The results show that MIPs made with 4-VPy yielded the best chiral separation factor (α = 1.86) for the template molecule. The importance for an efficient separation of pi-stacking interactions between the MIPs and the template molecule is demonstrated. Racemates of Z-α-amino acids and β-amino acid analogues of the template were either not or poorly resolved by the MIPs, thus demonstrating the close three-dimensional complementarity of the MIPs' recognition sites with the template.