Abstract
An ionic liquid (IL), 1-ethyl-3-methylimidazolium acetate [EMIM][CH3COO], was used in 0-4.0 M (∼60% IL, v/v), as a nonvolatile organic medium for the enzymatic resolution of amino acids. When dl-phenylalanine methyl ester was studied as a model substrate, high enantiomeric excesses (ee) of l-amino acid were obtained in all ionic concentrations; however, lower yields were observed at high IL concentrations. This IL is more enzyme-'friendly' than the hydrophilic organic solvent acetonitrile and those ILs containing chaotropic anions (such as [EMIM][OTs]). Among three proteases and two lipases investigated, lyophilized Bacillus licheniformis protease exhibited the best enantioselectivity and activity. Highly enantioselective resolutions were also produced for several other amino acids in 2.0 M IL. Interestingly, high ee were also found in deuterium oxide (D2O) rather than in ordinary water, and a further enhancement was achieved with the co-existence of [EMIM][CH3COO]. The heavy water effect was explained in terms of protein stabilization by D2O. The secondary structural changes of enzyme in various media were interpreted by the second derivatives of FT-IR spectra.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 2491-2498 |
| Number of pages | 8 |
| Journal | Tetrahedron Asymmetry |
| Volume | 17 |
| Issue number | 17 |
| DOIs | |
| State | Published - Oct 2 2006 |
| Externally published | Yes |
Bibliographical note
Funding Information:This project was supported by NSF HBCU-UP 2006 Research Program, and a CASTME Research Project under the Title III grant from the Department of Education.