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.
1-苯基和1-(
吡啶基)
乙酸酯的消旋酯1a–c(R=甲基,苯基)在皱褶假丝酵母脂酶(CRL)存在下
水解。1-
吡啶基
乙酸酯(1,R=甲基)在粗制CRL(C-CRL)和
异丙醇(异丙基
酒精)处理过的CRL(
PT-CRL)作用下的
水解速率非常低,且对映体识别令人失望。使用1-
吡啶基
苯甲酸酯(1,R=苯基)时结果大不相同:
水解速率快得多,且对映体识别对于3-和4-
吡啶衍生物良好,对于2-
吡啶衍生物非常优异。在相同实验条件下进行1-
苯乙醇酯4的酶促
水解也得到了类似的结果。甲基邻乙酰氧基
苯甲酸酯7(R=甲基)的
水解在C-CRL或
PT-CRL的作用下完全转化为脱乙酰化的甲基邻羟基
苯甲酸酯9(R=甲基)。在
PT-CRL催化的苯基邻乙酰氧基
苯甲酸酯7(R=苯基)的
水解中,观察到了完全相反的选择性。报道了旨在探究酶的三维结构对底物特异性和对映选择性的分子建模研究。