Highly enantioselective extraction of underivatized amino acids by the uryl-pendant hydroxyphenyl-binol ketone.
The hydroxyphenyl chiral ketone, (S)-3, reacts with D-amino acids bearing hydrophobic side chains exclusively over the L-amino acids in a two-phase liquid-liquid extraction, and thus acts as a highly stereoselective extractant. Calculations for the energy-minimized structures for the imine diastereomers and the comparison of the selectivities with other phenyl ketones, (S)-4 and (S)-5, demonstrate that the hydrogen bond between the carboxylate group and the phenolic hydroxyl group contributes to the remarkable enantioselectivities. The multiple hydrogen bonds present in the imine of (S)-3 reinforce the rigidity, and results in the difference between the stabilities of the imine diastereomers. The imine could be hydrolyzed in methanolic HCl solution, and the extraction of the evaporated residues revived the organic layer of (S)-3, which could enter into a new extractive cycle and leaves the D-amino acid with enantiomeric excess (ee) values of over 97 % in the aqueous layer.
College of Chemical Engineering, Shandong University of Technology, Zibo 255049 (P.R. China); Department of Chemistry and Nanosciences, Ewha Womans University, Daehyun-dong 11-1, Seoul 120-750 (Korea), Fax: (+81) 02-3277-3419.
Haofei
H
Huang
Qian
Q
Chen
Misun
M
Choi
Raju
R
Nandhakumar
Zhishan
Z
Su
Sihyun
S
Ham
Kwan Mook
KM
Kim
D000596:Amino Acids / Q000737:chemistry*; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D007097:Imines / Q000737:chemistry*; D007659:Ketones / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D015394:Molecular Structure; D009284:Naphthols / Q000737:chemistry*; D013237:Stereoisomerism
D000596:Amino Acids; C406944:BINOL, naphthol; D007097:Imines; D007659:Ketones; D009284:Naphthols
NMR spectroscopy; amino acids; chirality; density functional calculations; enantioselectivity; hydrogen bonds