Enantioselective liquid-liquid extractions of underivatized general amino acids with a chiral ketone extractant

The chiral ketone (S)-3 shows high kinetic enantioselectivities toward the l form for general underivatized amino acids with hydrophobic side chains and a high thermodynamic enantioselectivity toward the d form for cysteine with its -SH polar side chain when used as an extractant in enantioselective liquid-liquid extractions in the presence of Aliquat 336. Consecutive extractions by imine formation and hydrolysis increase the enantiopurity of the amino acid, as both of these reactions are l-form-selective.