Acetylation of (R,S)-propranolol catalyzed by Candida antarctica lipase B: An experimental and computational study
Acetylation of (R,S)-propranolol catalyzed by Candida antarctica lipase B: An experimental and computational study
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DOI：
10.1016/j.molcatb.2013.09.019
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发表时间：
2013-12-30
影响因子：
--
通讯作者：
Doerr, Markus
中科院分区：
文献类型：
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作者：
Escorcia, Andres M.;Molina, Daniel;Doerr, Markus
以醋酸乙烯酯为酰基供体，甲苯为有机溶剂，研究了南极假丝酵母脂肪酶B（CalB）催化（R，S）-普萘洛尔乙酰化反应的化学选择性和对映体选择性。由于普萘洛尔在甲苯中的溶解度差，因此加入少量甲醇作为助溶剂。考察了普萘洛尔/醋酸乙烯酯比例、酶纯化步骤和甲醇浓度对反应的影响。使用H-1和C-13 NMR光谱定量研究了体系中发生的反应。主要反应是醋酸乙烯酯的水解和醇解，这是由于反应介质中存在残留的水和甲醇。此外，NMR分析证实仅形成O-乙酰基-普萘洛尔。该反应也被发现是有利于R-普萘洛尔的更快转化的对映选择性。除了实验，分子建模用于研究普萘洛尔和乙酰化的CalB之间的反应性米氏络合物的形成，使用组合的分子对接和分子动力学（MD）程序。仅对于O-乙酰化，我们发现底物的结合模式导致产物的形成，这解释了实验观察到的CalB的化学选择性。(C)2013爱思唯尔有限公司版权所有。
The chemo- and enantioselectivity of the Candida antarctica lipase B (CalB)-catalyzed acetylation reaction of (R,S)-propranolol using vinyl acetate as acyl donor and toluene as organic solvent was studied. Because of the poor solubility of propranolol in toluene small quantities of methanol were added as cosolvent. The effects of the propranolol/vinyl acetate ratio, the enzyme purification procedure and the methanol concentration on the reaction were investigated. The reactions occurring in the system were quantitatively investigated using H-1 and C-13 NMR spectroscopy. The major reactions were the hydrolysis and alcoholysis of vinyl acetate, as a consequence of the presence of residual water and methanol in the reaction medium. Furthermore, the NMR analysis confirmed that O-acetyl-propranolol was formed exclusively. The reaction was also found to be enantioselective favoring the faster transformation of the R-propranolol. In addition to the experiments, molecular modeling was used to study the formation of the reactive Michaelis complexes between propranolol and acetylated CalB, using a combined molecular docking and molecular dynamics (MD) procedure. Only for the O-acetylation we found binding modes of the substrate leading to formation of the product, which explains the experimentally observed chemoselectivity of CalB. (C) 2013 Elsevier B.V. All rights reserved.