Chemoenzymatic dynamic kinetic resolution of α-trifluoromethylated amines: influence of substitutions on the reversed stereoselectivity
作者:Guilin Cheng、Bo Xia、Qi Wu、Xianfu Lin
DOI:10.1039/c3ra40526e
日期:——
Enzymatic resolution of α-trifluoromethylated amines via kinetic resolution (KR), dynamic kinetic resolution (DKR) employing CALB-Pd/Al2O3, and a one-pot sequential process of KR/DKR/KR was investigated comparatively for the first time. Although CALB-catalyzed KR of α-trifluoromethylated amines with substituents of methyl (1a), isopropyl (1c), phenyl (1d) and benzyl group (1e) can provide good stereoselectivity factors E from 31 to >200 respectively, DKR and sequential process of KR/DKR/KR possess better practical application potential because of the higher conversion (62%â84%) and the similar enantiomeric excesses (90%â99%). The enantiopreference and inversion for the α-trifluoromethylated amines displayed by CALB were observed and explained by docking modes. Namely, for 1,1,1-trifluoro-2-propylamine (1a), the product amide with R-configuration was obtained, and the enantiopreference was converted to S for the amines (1bâ1e) with substituents larger than methyl group. The catalysts recycle, and scale-up experiments were demonstrated successfully. All these results indicated the high efficiency and green feature of this enzymatic process, and its application significance.
首次比较研究了通过动力学分辨 (KR)、动态动力学分辨 (DKR) 采用 CALB-Pd/Al2O3 催化,及 KR/DKR/KR 一锅顺序过程对 α-三氟甲基化胺的酶解分辨。尽管 CALB 催化的 α-三氟甲基化胺与甲基 (1a)、异丙基 (1c)、苯基 (1d) 和苄基 (1e) 取代基的 KR 可以提供良好的立体选择性因子 E,从 31 到超过 200,但 DKR 和 KR/DKR/KR 的顺序过程由于更高的转化率 (62%–84%) 和相似的对映体过量 (90%–99%),具有更好的实际应用潜力。通过分子对接模式观察并解释了 CALB 显示出的对 α-三氟甲基化胺的对映选择性和反转。即对于 1,1,1-三氟-2-丙胺 (1a),获得了 R 构型的酰胺产物,对于取代基大于甲基的胺 (1b–1e),对映选择性则转换为 S。催化剂的回收和放大实验成功演示。这些结果表明该酶促过程高效且环保,具有重要的应用意义。