Influence of ionic liquids on the rates and regioselectivity of lipase-mediated biotransformations on 3,4,6-tri-O-acetyl-d-glucal

Lipase-mediated regioselective biotransformations such as hydrolysis and alcoholysis of 3,4,6-tri-O-acetyl-d-glucal, 1 have been studied in organic solvent, tetrahydrofuran (THF) and two different ionic liquids, namely 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF6 and 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF4. The influence of different reaction media on the rates and regioselectivity of enzyme catalysis has been demonstrated. A marked regioselectivity towards the formation of 4,6-di-O-acetyl-d-glucal, 2 was observed in [bmim]PF6 with 84% product formation after 6 h with 98% selectivity in hydrolysis and 48% after 8 h with 98% selectivity in alcoholysis.