AbstractTo establish a system for the efficient one bacterial multi‐enzymatic biosynthesis of both (R)‐ and (S)‐β‐hydroxy nitriles, we co‐expressed alcohol dehydrogenases with opposite stereoselectivities, cofactor regeneration enzymes, and a halohydrin dehalogenase in Escherichia coli. By researching cofactor recycling and various co‐expression strategies and by selecting and engineering the halohydrin dehalogenase, we engineered two E. coli strains, which were subsequently used in a cascade of reactions to produce chiral β‐hydroxy nitriles with high enantiomeric excess directly from prochiral α‐halo ketones. Three valuable pharmaceutical intermediates were prepared by means of this catalytic system, and substrate conversion reached about >99%. More importantly, the system is of low cost because there is no need for expensive cofactors or for expression and purification of the component enzymes.magnified image
卤化有机污染物(HOP)由于其高毒性、持久性和生物累积性,正在造成严重的环境和人类健康危机。需要采取紧急行动来制定减少和再利用 HOP 的有效方法。虽然目前的策略主要集中在 HOP 的降解上,但重新利用它们是一种替代方法,尽管这是一项具有挑战性的任务。在这里,我们发现烷基溴可以作为使用烷基氯作为氯源的氯转移的催化剂。我们证明这种方法具有广泛的底物范围,并成功地将其应用于重复使用 HOP,包括二氯二苯基三氯乙烷、六溴环十二烷、氯化石蜡、氯甲基聚苯乙烯和聚氯乙烯 (PVC)。此外,我们还表明,使用PVC和六溴环十二烷可以合成必需的非甾体抗炎药,并且我们证明PVC废料可以直接用作氯化剂。总体而言,这种方法为重新利用 HOP 提供了一种有前景的策略。
Highly regio- and diastereoselective halohydroxylation of olefins: a facile synthesis of vicinal halohydrins
作者:Jinglei Zhang、Jie Wang、Zhuibai Qiu、Yang Wang
DOI:10.1016/j.tet.2011.06.077
日期:2011.9
out under mild conditions in the presence of N-tosyl-l-threonine (NTsLT) as an acidic additive using chloramine T trihydrate, 1,3-dichloro-5,5-dimethylhydantoin (DCDMH) or N-bromoacetamide (AcNHBr) as the halogen source, respectively, affording the corresponding vicinal halohydrins in good to high yields with excellent regio- and stereoselectivities.
We report a palladium-free Wacker-type oxidation of styrenes using CuCl2/KBr as the catalyst and trichloroisocyanuric acid as a stoichiometric chlorine radical source. The reaction protocol is compatible with diverse functional groups, affording selectively acetophenones. The mechanistic analysis revealed that a site-selective sequential CuII-photooxidation/CuI-photoreduction of the intermediary chlorohydrin
我们报道了使用 CuCl 2 /KBr 作为催化剂和三氯异氰尿酸作为化学计量氯自由基源的苯乙烯的无钯瓦克型氧化。该反应方案与不同的官能团兼容,选择性地提供苯乙酮。机理分析表明,中间氯醇的位点选择性顺序Cu II -光氧化/Cu-光还原是这一转化成功的关键。