Biocatalysis and Enzyme Engineering Laboratory, Department of Biochemistry, School of Life Sciences, University of Hyderabad, Hyderabad, 500046, India.
Appl Biochem Biotechnol. 2021 Feb;193(2):560-576. doi: 10.1007/s12010-020-03442-3. Epub 2020 Oct 12.
Enantiopure β-nitroalcohols are versatile intermediates used in the synthesis of important pharmaceuticals and chiral synthons. In this article, immobilized Arabidopsis thaliana HNL (AtHNL)-catalyzed preparation of (S)-β-nitroalcohols from their racemic mixtures via retro-Henry reaction was studied. AtHNL used in biocatalysis was immobilized by physical adsorption in inexpensive celite®545. Under optimized biocatalytic conditions, the total turnover number of the catalyst has improved 2.3-fold for (S)-2-nitro-1-phenylethanol (NPE) synthesis, than free enzyme catalysis. This study reported for the first time celite-AtHNL-catalyzed retro-Henry reaction at low pH. At pH 4.5 and 5.0, 62% ee and 41% conversion, and 97% ee and 42% conversion of (S)-NPE were obtained respectively, while the free enzyme inactivates at pH < 5.0. The increased catalytic efficiency and pH stability of the catalyst could be possibly due to increased stability of AtHNL by immobilization. A dozen of racemic β-nitroalcohols were converted into their corresponding (S)-β-nitroalcohols using this reaction; among them, eight were not tested earlier. The immobilized enzyme has showed broad substrate selectivity in the retro-Henry reaction, and products were obtained up to 98.5% ee.
手性纯 β-硝基醇是合成重要药物和手性砌块的多功能中间体。本文研究了拟南芥 HNL（AtHNL）固定化酶通过反 Henry 反应从外消旋混合物中制备（S）-β-硝基醇。在生物催化中使用的 AtHNL 通过物理吸附固定在廉价的 Celite®545 上。在优化的生物催化条件下，与游离酶催化相比，（S）-2-硝基-1-苯乙醇（NPE）合成的催化剂总周转数提高了 2.3 倍。本研究首次报道了 Celite-AtHNL 催化的低 pH 值反 Henry 反应。在 pH 4.5 和 5.0 时，分别获得了 62%ee 和 41%转化率，以及 97%ee 和 42%转化率的（S）-NPE，而游离酶在 pH<5.0 时失活。催化剂的催化效率和 pH 稳定性的提高可能是由于固定化增加了 AtHNL 的稳定性。使用该反应将十几个外消旋 β-硝基醇转化为相应的（S）-β-硝基醇；其中，有八个之前没有进行过测试。固定化酶在手性纯β-硝基醇的反 Henry 反应中表现出广泛的底物选择性，产物的对映体过量值高达 98.5%。
