Highly Enantioselective Extraction of Underivatized Amino Acids by the Uryl‐Pendant Hydroxyphenyl‐Binol Ketone |
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| Authors: | Dr. Haofei Huang Qian Chen Misun Choi Prof. Raju Nandhakumar Dr. Zhishan Su Prof. Dr. Sihyun Ham Prof. Kwan Mook Kim |
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| Affiliation: | 1. College of Chemical Engineering, Shandong University of Technology, Zibo 255049 (P.R. China);2. Department of Chemistry and Nanosciences, Ewha Womans University, Daehyun‐dong 11‐1, Seoul 120‐750 (Korea), Fax: (+81)?02‐3277‐3419;3. Department of Chemistry, Karunya University, Coimbatore‐641 114, TamilNadu (India);4. Key Laboratory of Green Chemistry and Technology, Ministry of Education, College of Chemistry, Sichuan University, Chengdu 610064 (P.R. China);5. Department of Chemistry, Sookmyung Women's University, Cheongpa‐ro 47‐gil 100, Seoul 140‐742 (Korea) |
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| Abstract: | 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. |
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| Keywords: | amino acids chirality density functional calculations enantioselectivity hydrogen bonds NMR spectroscopy |
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