Regioselective acylation of pyridoxine catalyzed
by immobilized lipase in ionic liquid |
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Authors: | BAI Shu REN Mengyuan WANG Lele SUN Yan |
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Affiliation: | Department of Biochemical Engineering, School of Chemical Engineering and Technology, Tianjin University |
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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 (aw) 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 aw (<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. |
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