Racemic esters of 1-phenyl- and 1-(pyridyl)ethyl acetates 1a–c (R = Me, Ph) were subjected to hydrolysis in water in the presence of Candida rugosa lipase (CRL). 1-Pyridylethyl acetates (1, R = Me) are hydrolyzed by crude CRL (C-CRL) and isopropanol (isopropyl alcohol) treated CRL (PT-CRL) at very low rates, and the enantiorecognition was disappointing. By using 1-pyridylethyl benzoates (1, R = Ph) the results differed greatly: hydrolysis occurred much faster, and the enantiorecognition was good for 3- and 4-pyridyl derivatives and excellent for 2-pyridyl derivative. Analogous results were obtained by submitting the 1-phenylethanol esters 4 to enzymatic hydrolysis under the same experimental conditions. The hydrolysis of methyl o-acetoxybenzoates 7 (R = Me) gave quantitatively the deacetylated methyl o-hydroxybenzoates 9 (R = Me) by using either C-CRL or PT-CRL. A complete reversed selectivity is observed in the hydrolysis of phenyl o-acetoxybenzoates 7 (R = Ph) catalyzed by PT-CRL. Molecular modeling studies, aimed at probing the substrate specificity and the enantioselectivity of enzyme in terms of its three-dimensional structure is reported.
The Importance of Ester and Alkoxy Type Functionalities for the Chemo- and Enantio-Recognition of Substrates by Hydrolysis Candida Rugosa Lipase
BELLEZZA, Francesca;CIPICIANI, Antonio;CRUCIANI, Gabriele;FRINGUELLI, Francesco
2000
Abstract
Racemic esters of 1-phenyl- and 1-(pyridyl)ethyl acetates 1a–c (R = Me, Ph) were subjected to hydrolysis in water in the presence of Candida rugosa lipase (CRL). 1-Pyridylethyl acetates (1, R = Me) are hydrolyzed by crude CRL (C-CRL) and isopropanol (isopropyl alcohol) treated CRL (PT-CRL) at very low rates, and the enantiorecognition was disappointing. By using 1-pyridylethyl benzoates (1, R = Ph) the results differed greatly: hydrolysis occurred much faster, and the enantiorecognition was good for 3- and 4-pyridyl derivatives and excellent for 2-pyridyl derivative. Analogous results were obtained by submitting the 1-phenylethanol esters 4 to enzymatic hydrolysis under the same experimental conditions. The hydrolysis of methyl o-acetoxybenzoates 7 (R = Me) gave quantitatively the deacetylated methyl o-hydroxybenzoates 9 (R = Me) by using either C-CRL or PT-CRL. A complete reversed selectivity is observed in the hydrolysis of phenyl o-acetoxybenzoates 7 (R = Ph) catalyzed by PT-CRL. Molecular modeling studies, aimed at probing the substrate specificity and the enantioselectivity of enzyme in terms of its three-dimensional structure is reported.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
