Regioselective acylation of pyridoxine catalyzed by immobilized lipase in ionic liquid

Abstract

The regioselective acylation of pyridoxine catalyzed by immobilized lipase (Candida Antarctica) in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF₆) has been investigated, and compared with that in acetonitrile (ACN). The acetylation of pyridoxine using acetic anhydride in [BMIM]PF₆ gave comparable conversion of pyridoxine to 5-monoacetyl pyridoxine with considerably higher regioselectivity (93%–95%) than that in ACN (70%–73%). Among the tested parameters, water activity (a_w) and temperature have profound effects on the reaction performances in either [BMIM]PF₆ or ACN. For the reaction in [BMIM]PF₆, higher temperature (50°C–55°C) and lower a_w (<0.01) are preferable conditions to obtain better conversion and regioselectivity. Mass transfer limitation and intrinsic kinetic from the ionic nature of ionic liquids (ILs) may account for a different rate-temperature profile and a lower velocity at lower temperature in [BMIM]PF₆-mediated reaction. Moreover, consecutive batch reactions for enzyme reuse also show that lipase exhibited a much higher thermal stability and better reusability in [BMIM]PF₆ than in ACN, which represents another advantage of ILs as an alternative to traditional solvents beyond green technology.

References

1. Fonda M L . Vitamin B6 metabolism and binding to proteins in the blood of alcoholicand nonalcoholic men. Alcohol Clin ExpRes, 1993, 17: 1171–1178. doi:10.1111/j.1530‐0277.1993.tb05223.x
2. DeSimone J M . Practical approaches to green solvents. Science, 2002, 297: 799–803. doi:10.1126/science.1069622
3. Wasserscheid P, Welton T . Ionic liquids in synthesis. Weinheim: Wiley-VCH, 2003
4. Dupont J, Souza R F, Suarez P A Z . Ionic liquid (Molten salt) phase organometallic catalysis. Chem Rev, 2002, 102: 3667–3692. doi:10.1021/cr010338r
5. Kragl U, Eckstein M, Kaftzik N . Enzyme catalysis in ionic liquid. Curr Opin Biothchnol, 2002, 13: 565–570. doi:10.1016/S0958‐1669(02)00353‐1
6. Park S, Kazlauskas R J . Biocatalysis in ionic liquids-advantagesbeyond green technology. Curr Opin Biotechnol, 2003, 14: 432–437. doi:10.1016/S0958‐1669(03)00100‐9
7. Brennecke J F, Maginne E J . Ionic liquids: Innovativefluids for chemical processing. AIChE J, 2001, 47: 2384–2389. doi:10.1002/aic.690471102
8. Guo Z, Xu X . New opportunity for enzymaticmodification of fats and oils with industrial potentials. Org Biomol Chem, 2005, 3: 2615–2619. doi:10.1039/b506763d
9. Lee S G . Functionalized imidazolium salts for task-specific ionic liquidsand their applications. Chem Commun, 2006, 1049–1063
10. Schöfer S H, Kaftzik N, Wasserscheid P, Kragl U . Enzyme catalysisin ionic liquids: lipase catalysed kinetic resolution of 1-phenylethanolwith improved enantioselectivity. ChemCommun, 2001, 425–426
11. Kim M J, Choi M Lee J K, Ahn Y . Enzymatic selective acylation of glycosides in ionicliquids: Significantly enhanced reactivity and regioselectivity. J Mol Catal B: Enzyme, 2003, 26: 115–118. doi:10.1016/j.molcatb.2003.04.001
12. Li X F, Lou W Y, Smith T J, Zong M H, Wu H, Wang J F . Efficientregioselective acylationof 1-β-D-arabinofuranosylcytosine catalyzedby lipase in ionic liquid containing systems. Green Chem, 2006, 8: 538–544. doi:10.1039/b600397d
13. Itoh T, Akasaki E, Kudo K, Shirakami S . Lipase-catalysedenantioselective acylation in the ionic liquid solvent system: reactionof enzyme anchored to the solvent. ChemLett, 2001, 1: 262–263. doi:10.1246/cl.2001.262
14. Baldessari A, Mangone C P, Gros E G . Lipase-catalyzed acylation and deacylation reactionsof pyridoxine, a member of Vitamin-B6 group. Helvetica Chimica Acta, 1998, 81: 2407–2413. doi:10.1002/(SICI)1522‐2675(19981216)81:12<2407::AID‐HLCA2407>3.0.CO;2‐X
15. Wilkes J S . A short history of ionic liquids-from molten salts to neoteric solvents. Green Chem, 2002, 4: 73–80. doi:10.1039/b110838g
16. Song C E . Enantioselective chemo- and bio-catalysis in ionic liquids. Chem Common, 2004, 1033–1043
17. Barahona D, Pfromm P H, Rezac M E . Effects of water activity on the lipase catalyzed esterificationof geraniol in ionic liquid [bmim]PF6. Biotechnol Bioeng, 2005, 93: 318–324. doi:10.1002/bit.20723
18. Earle M J, McCormac P B, Seddon K R . The first high yield green route to a pharmaceuticalin a room temperature ionic liquid. GreenChem, 2000, 2: 261–262. doi:10.1039/b006612p
19. Huddleston J G, Willauer H D, Swatloki R P . Room temperature ionic liquids as novel media for ‘clean'liquid-liquid extraction. J Chem Soc ChemComm, 1998, 1765–1766
20. Park S, Kazlauskas R J . Improved preparation anduse of room-temperature ionic liquids in lipase-catalyzed enantio-and regioselective acylations. J Org Chem, 2001, 66: 8395–8401. doi:10.1021/jo015761e
21. Halling P J . Salt hydrates for water activity control with biocatalysis in organicmedia. Biotechnol Tech, 1992, 6: 271–276. doi:10.1007/BF02439357
22. Guo Z, Xu X . Lipase-catalyzed glycerolysisof fats and oils in ionic liquids: a further study on the reactionsystem. Green Chemistry, 2006, 8: 54–62. doi:10.1039/b511117j
23. Aggarwal A, Lancaster N L, Sethi A R, Welton T . The role ofhydrogen bonding in controlling the selectivity of Diels-Alder reactionsin room-temperature ionic liquids. GreenChem, 2002, 4: 517–520. doi:10.1039/b206472c
24. Guo Z, Chen B, Murillo R L, Tan T, Xu X . Functional dependency of structures of ionic liquids:do substituents govern the selectivity of enzymatic glycerolysis?Org Biomol Chem, 2006, 4: 2772–2776. doi:10.1039/b606900b
25. Halling P J . Thermodynamic predictions for biocatalysis in nonconventional media:theory, tests, and recommendations for experimental design and analysis. Enzyme Microb Technol, 1994, 16: 178–206. doi:10.1016/0141‐0229(94)90043‐4
26. Berberich J A, Kaar J L, Russell A J . Use of salt hydrate pairs to control water activity forenzyme catalysis in ionic liquids. BiotechnolProg, 2003, 19: 1029–1032. doi:10.1021/bp034001h
27. Bell G, Janssen A E M, Halling P J . Water activity fails to predict critical hydration levelfor enzyme activity in polar organic solvents: interconversion ofwater concentrations and activities. EnzymeMicrob Technol, 1997, 20: 471–477. doi:10.1016/S0141‐0229(96)00204‐9
28. Lozano P, Carrié D, Vaultier M, Iborra J L . Over-stabilizationof Candida antarctica lipase B by ionic liquids in ester synthesis. Biotechnol Lett, 2001, 23: 1529–1533. doi:10.1023/A:1011697609756
29. Park S, Kazlauskas R J . Biocatalysis in ionic liquids-advantagesbeyond green technology. Curr Opin Biotechnol, 2003, 14: 432–437. doi:10.1016/S0958‐1669(03)00100‐9