Abstract
The regioselective monohydrolysis of different peracetylated-beta-glucopyranosides in aqueous media using immobilized preparations of three different lipases-those from Aspergillus niger (ANL), Candida rugose (CRL) and Candida antarctica B (CAL-B)-has been Studied. Three very different immobilization strategies-covalent attachment, anionic exchange and interfacial activation oil a hydrophobic sopport-were employed for each lipase. The role of the immobilization strategy and the effect of the presence of different moieties in the anomeric position of the substrate on the hydrolytic activities, specificities and regioselectivities of the lipases were investigated. For example, the PEI-ANL preparation exhibited 800 times higher activity than the octyl-ANL in the hydrolysis of 2-acetamido-2-deoxy-1-(4-nitrophenyl)-3,4,6-tri-O-acetyl-beta-D-glucopyranoside-producing 4-OH derivative in 18% yield-whereas the octyl-ANL was five times more active than the PEI-ANL in the hydrolysis of 1-(4-nitrophenyl)-2,3,4-tri-O-acetyl-beta-D-xylopyranoside, producing 4-OH monohydroxy product in >99% yield.
The octyl-CRL preparation hydrolyzed regioselectively 3,4,6-tri-O-acetyl-glucal in position 6 in 68% yield while the PEI-CRL produced the 3-OH product in 11% yield, although with moderate specificity. The CNBr-CAL-B hydrolyzed specifically and regioselectively the glucal producing the 3-OH product in >99% yield. (C) 2008 Elsevier Ltd. All rights reserved.