Regioselective enzymatic hydrolysis of acetylated pyranoses and pyranosides using immobilised lipases. An easy chemoenzymatic synthesis of α- and β-d-glucopyranose acetates bearing a free secondary C-4 hydroxyl group

Regioselective C‐6 Hydrolysis of MethylO‐Benzoyl‐pyranosides Catalysed byCandida RugosaLipase

“…Also the hydrolysis of methyl and butyl 2,3,4,6-tetra-O-acetyl α--and β--glucopyranosides proceeded regioselectively at C-6 at pH 4 using 25 % acetonitrile as a co-solvent. [20] Good regiocontrol was also observed in hydrolysis of methyl 2,3,4,6-tetra-O-acetyl-α--mannopyranoside. [28] Hydrolysis of acetylated hexapyranosides using a PEG-modified variant of CRL in 1,1,1-trichloroethane/water lead to mixtures of methyl 2,3-diacetyl hexapyranosides and methyl 2,3,4-triacetyl hexapyranosides.…”

“…[19] As opposed to standard methods, regioselective hydrolysis catalysed by enzymes offers a two step route. [20][21][22][23][24] Candida rugosa lipase (CRL) has proven to be the catalyst of choice for deacetylation at C-6. [20,24] The lipase has a rather wide active site and the ability to tolerate high concentrations of organic co-solvents.…”

“…[20][21][22][23][24] Candida rugosa lipase (CRL) has proven to be the catalyst of choice for deacetylation at C-6. [20,24] The lipase has a rather wide active site and the ability to tolerate high concentrations of organic co-solvents. [25][26][27] The hydrolysis of glucose pentaacetate has been investigated at different pH by several authors.…”

“…[25][26][27] The hydrolysis of glucose pentaacetate has been investigated at different pH by several authors. [20,23,24] Reactions at pH 4-5 using CRL led to high regioselectivity favouring hydrolysis at C-6, whereas at methyl 2,3,4,6-tetra-O-benzoyl-β-D-galactopyranoside substrate inhibition were observed, which in part could be overcome by increasing the reaction volume. Methyl 2,3,4,6-tetra-O-benzoyl-β-D-glucopyranoside and methyl 2,3,4,6-tetra-O-benzoyl-α-D-mannopyranoside were poor substrates for Candida rugosa lipase and low degree of conversion towards products were obtained under all conditions.…”

“…[21,30] A disadvantage with pyranoside acetates is their tendency to undergo acyl migrations. [20,21,31] Benzoyl migration in carbohydrate chemistry is not unknown. [32,33] However, due to their higher stability towards base, [34] benzoate pyranosides are expected to be less problematic in this respect compared to their acetylated analogues.…”