Biocatalytical approaches have been investigated in order to improve accessibility of the bifunctional chiral building block (5S)-hydroxy-2-hexanone ((S)-2). As a result, a new synthetic route starting from 2,5-hexanedione (1) was developed for (S)-2, which is produced with high enantioselectivity (ee >99%). Since (S)-2 can be reduced further to furnish (2S,5S)-hexanediol ((2S,5S)-3), chemoselectivity is a major issue. Among the tested biocatalysts the whole-cell system S. cerevisiae L13 surpasses the bacterial dehydrogenase ADH-T in terms of chemoselectivity. The use of whole-cells of S. cerevisiae L13 affords (S)-2 from prochiral 1 with 85% yield, which is 21% more than the value obtained with ADH-T. This is due to the different reaction rates of monoreduction (1→2) and consecutive reduction (2→3) of the respective biocatalysts. In order to optimise the performance of the whole-cell-bioreduction 1→2 with S. cerevisiae, the system was studied in detail, revealing interactions between cell-physiology and xenobiotic substrate and by-products, respectively. This study compares the whole-cell biocatalytic route with the enzymatic route to enantiopure (S)-2 and investigates factors determining performance and outcome of the bioreductions.
为了提高双功能手性结构单元 (5S)-hydroxy-2-hexanone ((S)-2)的可及性,我们研究了
生物催化方法。因此,以
2,5-己二酮 (1) 为起点的 (S)-2 新合成路线被开发出来,其生产具有很高的对映选择性(ee >99%)。由于(S)-2 可以进一步还原生成 (2S,5S)-
己二醇((2S,5S)-3),因此
化学选择性是一个主要问题。在测试的
生物催化剂中,全
细胞系统 S. cerevisiae L13 的
化学选择性超过了细菌脱氢酶 ADH-T。使用全细胞 S. cerevisiae L13 从原手性 1 中生成 (S)-2 的产率为 85%,比 ADH-T 高出 21%。这是因为两种
生物催化剂的单还原(1→2)和连续还原(2→3)反应速率不同。为了优化全细胞
生物还原 1→2 与 S. cerevisiae 的性能,对该系统进行了详细研究,分别揭示了细胞生理学与异
生物底物和副产物之间的相互作用。本研究比较了全细胞
生物催化途径和酶法途径制备对映体纯(S)-2 的方法,并研究了决定
生物还原的性能和结果的因素。