Mattson A, Boutelje J, Csöregh I, Hjalmarsson M, Jacobsson U, Lindbäck M, Norin T, Szmulik P, Hult K
Department of Chemistry, Royal Institute of Technology, Stockholm, Sweden.
Bioorg Med Chem. 1994 Jun;2(6):501-8. doi: 10.1016/0968-0896(94)80020-0.
The enantioselectivity of pig liver esterase catalysed hydrolysis of cis-N-benzyl-2,5-bis(methoxy-carbonyl)pyrrolidine (1) has previously been shown to be very dependent on the reaction conditions. Hydrolysis performed in media buffered with tris(hydroxymethyl)aminomethane (Tris) afforded a monoester with much higher optical purity than hydrolysis in media without Tris. Detailed product studies in a Tris-buffered medium have been performed using NMR-techniques and a 13C-labelled ester. The NMR-studies revealed the presence of (2S,5R)-N-benzyl-2-methoxycarbonyl-5-[[[2-hydroxy-1,1- bis(hydroxymethyl)ethyl]amino]carbonyl]pyrrolidine (4) as an intermediate, which together with the isolated product (2S,5R)-N-benzyl-2-carboxy-5-[[[2-hydroxy-1,1-bis(hydroxymethyl) ethyl]amino]carbonyl]pyrrolidine (3) suggested Tris as a competitive nucleophile to water. The increased enantioselectivity seen in the produced (2R,5S)-N-benzyl-2-methoxy-carbonyl-5-carboxypyrrolidine (2) was explained by the preference of Tris to react faster with one of the diastereomeric acyl enzymes over the other.
猪肝酯酶催化顺式-N-苄基-2,5-双（甲氧基羰基）吡咯烷（1）水解的对映选择性先前已表明非常依赖于反应条件。在由三（羟甲基）氨基甲烷（Tris）缓冲的介质中进行的水解比在没有Tris的介质中水解得到的单酯具有高得多的光学纯度。使用NMR技术和13C标记的酯在Tris缓冲介质中进行了详细的产物研究。NMR研究揭示了（2S,5R）-N-苄基-2-甲氧基羰基-5-[[[2-羟基-1,1-双（羟甲基）乙基]氨基]羰基]吡咯烷（4）作为中间体的存在，其与分离产物（2S,5R）-N-苄基-2-羧基-5-[[[2-羟基-1,1-双（羟甲基）乙基]氨基]羰基]吡咯烷（3）一起表明Tris作为水的竞争性亲核试剂。所产生的（2R,5S）-N-苄基-2-甲氧基羰基-5-羧基吡咯烷（2）中观察到的对映选择性增加是由于Tris优先与一种非对映异构酰基酶反应比另一种更快。
