Improved preparation and use of room-temperature ionic liquids in lipase-catalyzed enantio- and regioselective acylations.
Polar organic solvents such as methanol or N-methylformamide inactivate lipases. Although ionic liquids such as 3-alkyl-1-methylimidazolium tetrafluoroborates have polarities similar to these polar organic solvents, they do not inactivate lipases. To get reliable lipase-catalyzed reactions in ionic liquids, we modified their preparation by adding a wash with aqueous sodium carbonate. Lipase-catalyzed reactions that previously did not occur in untreated ionic liquids now occur at rates comparable to those in nonpolar organic solvents such as toluene. Acetylation of 1-phenylethanol catalyzed by lipase from Pseudomonas cepacia (PCL) was as fast and as enantioselective in ionic liquids as in toluene. Ionic liquids permit reactions in a more polar solvent than previously possible. Acetylation of glucose catalyzed by lipase B from Candida antarctica (CAL-B) was more regioselective in ionic liquids because glucose is up to one hundred times more soluble in ionic liquids. Acetylation of insoluble glucose in organic solvents yielded the more soluble 6-O-acetyl glucose, which underwent further acetylation to give 3,6-O-diacetyl glucose (2-3:1 mixture). However, acetylation of glucose in ionic liquids yielded only 6-O-acetyl glucose (>13:1 and up to >50:1).
Park
S
S
McGill University, Department of Chemistry, 801 Sherbrooke Street West, Montréal, Québec H3A 2K6, Canada.
Kazlauskas
R J
RJ
D000215:Acylation; D016956:Burkholderia cepacia / Q000737:chemistry; D002175:Candida / Q000737:chemistry; D002384:Catalysis; D005559:Formamides / Q000737:chemistry; D005656:Fungal Proteins; D005947:Glucose / Q000737:chemistry; D007093:Imidazoles / Q000737:chemistry; D007477:Ions; D008049:Lipase / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D012997:Solvents; D013237:Stereoisomerism; D013696:Temperature
D005559:Formamides; D005656:Fungal Proteins; D007093:Imidazoles; D007477:Ions; D011725:Pyridines; D012997:Solvents; D008049:Lipase; C431349:lipase B, Candida antarctica; D005947:Glucose; C002950:methylformamide; D000432:Methanol