酶催化的动态动力学拆分和去消旋化反应的研究进展

最近,在外消旋化合物的动态动力学拆分以及去消旋化反应方面,新型催化剂的发现以及反应条件的优化都得到了很大的发展。一些特殊功能团使得它们的化合物可以发生动态动力学拆分或是去消旋反应,如仲醇、α-氨基酸、胺及羧酸。在催化反应过程中,一般都是对映体选择性酶与化学试剂的相结合,化学试剂一般常用于催化非活性对映体发生去消旋反应或是回收去消旋化过程中的中间体。在一些动态动力学拆分中,消旋酶还可以催化对映异构体之间发生互变。     

化学-酶催化动态动力学拆分工艺中多相催化剂的研究进展

利用外消旋体进行化学-酶催化动态动力学拆分是制备单一手性化合物的有效手段之一。论述了近几年用于动态动力学拆分工艺中的固定化脂肪酶和固相外消旋化多相催化剂的研究进展,介绍了过渡金属配合物、酸性β-沸石和酸性树脂等固相外旋消化催化剂与固定化脂肪酶配伍,用于化学-酶催化动态动力学拆分工艺的催化效果。     

动态动力学拆分制备手性化合物的研究进展

综述了固体酸、固体碱和金属配合物在动态动力学拆分制备光学纯手性化合物进行外消旋化的催化机理,讨论了均相外消旋催化剂和多相外消旋催化剂在动态动力学拆分工艺中的应用,重点介绍了过渡金属配合物催化剂和生物酶配伍进行动态动力学拆分制备手性化合物的研究进展和发展趋势。     

单层分散(L)-脯氨酸修饰的Pd/Al2O3催化剂上3,3,5-三甲基环己酮的动力学拆分

由异佛尔酮(IP)不对称加氢产物得到的手性(R-或S-)3,3,5-三甲基环己酮(TMCH)是非常重要的精细化工中间体。该文探究了(L)-脯氨酸修饰Pd/Al2O3催化剂上异佛尔酮的不对称加氢和3,3,5-三甲基环己酮外消旋体的催化加氢动力学拆分。研究发现,异佛尔酮和(L)-脯氨酸的缩合物会显著抑制异佛尔酮的不对称加氢反应。(L)-脯氨酸在Pd/Al2O3加氢催化剂表面容易发生自发单层分散,有效提高3,3,5-三甲基环己酮外消旋体加氢拆分产物的ee值。在(L)-脯氨酸单层分散的Pd/Al2O3催化剂上,反应温度为40℃、压力为1 MPa、反应时间为10 h时,3,3,5-三甲基环己酮外消旋体加氢拆分产物的ee值达到100%。     

桃醛的外消旋物的分离研究进展

桃醛是一种重要的内酯香料,可广泛应用于日化香精和食用香精。桃醛是手性香料,其R-异构体具有独特的商业价值,而关于外消旋体的拆分报道较少,文中简单介绍了由化学合成得到的桃醛外消旋体的化学拆分、酶动力学拆分和色谱拆分法,期望对以后桃醛的外消旋体的拆分研究给予帮助。     

动态动力学拆分方法在不对称催化中的应用与进展

不对称催化在有机合成中具有广阔的应用前景。传统的动力学拆分方法的缺点是最大产率仅为 5 0 %。而采用动态动力学拆分方法 ,所有外消旋底物都能转化成单一的对映体 ,产率为 10 0 %。主要论述了酶催化的动力学拆分、金属催化的外消旋作用及两者相结合的动态动力学拆分方法的原理和应用     

手性化合物的非目标对映体转化

介绍了通过构型反转和外消旋化反应对手性醇类、氨基醇类和氨基酸类化合物的非目标对映体进行转化的最新研究进展。构型反转能够直接得到所需要的对映体,效率高,但其应用局限性较大;而催化外消旋化反应的应用范围更加广泛,尤其是将金属配合物与酶联用的动态动力学拆分法使消旋率达到了100%,并最终直接得到所需构型的对映体,应是今后研究的重点,同时固定床连续外消旋化的方法也具有良好的应用前景。     

手性Salen Co(Ⅱ)催化剂催化环氧氯丙烷的最佳水解动力学条件研究

实验以手性Salen Co（Ⅱ）为催化剂,对外消旋的环氧氯丙烷进行水解动力学拆分。实验选用正交试验的设计方法,选取了4个因素,3个水平,进行了9次正交实验。对实验结果（水解产物（S）-环氧氯丙烷的旋光性）进行极差分析处理,研究了反应温度、反应时间、催化剂用量,蒸馏水用量等反应条件对拆分效果的影响及影响的大小,并优化出环氧氯丙烷水解动力学拆分反应的最佳动力学条件。     

酰基供体对动态动力学拆分1-四氢萘胺的影响

采用新型消旋催化剂耦合Novozym 435成功构建1-四氢萘胺的动态动力学拆分体系用于制备光学纯(R)-1-四氢萘胺。该反应存在着自催化酰胺化反应,会降低反应的对映体选择性。从改变酰基供体结构的角度出发来抑制这种自催化酰胺化反应,考察了不同酸部以及不同醇部的酰基供体对1-四氢萘胺动态动力学拆分反应的影响,发现随着酰基供体结构变得复杂,1-四氢萘胺动态动力学拆分反应结果也相应变得越好,当采用戊酸对氯苯酯作为酰基供体时,动态动力学拆分反应结果就可达到最佳,即转化率>99%,光学纯度eeP>99%。     

手性反应控制进展

现在越来越多的方法应用到用酶高效催化手性非外消旋化合物的对映性选择反应中来.对于不对称性合成反应或者动力学拆分的替代反应有动态动力学拆分、去消旋化和对映会聚转化等.另外,人们对影响反应生成的立体化学产物的参数(如溶剂、底物设计、固定化、定向进化等)有了进一步的了解.     

Dynamic Kinetic Resolution of Primary Alcohols with an Unfunctionalized Stereogenic Center in the β‐Position

Primary alcohols with an unfunctionalized stereogenic center in the β‐position undergo an enzyme‐ and metal‐catalyzed dynamic kinetic resolution (DKR). The in situ racemization of the primary alcohol, required for the DKR, takes place via: (i) ruthenium‐catalyzed dehydrogenation of the alcohol, (ii) enolization of the aldehyde formed, and (iii) ruthenium‐catalyzed readdition of hydrogen to the aldehyde. The present method widens the scope of metal‐ and enzyme‐catalyzed DKR, which has so far been limited to α‐chiral alcohol and amine derivatives.     

Organocatalyzed Dynamic Kinetic Resolution

In the last decade, the first examples of organocatalyzed dynamic kinetic resolution (DKR) processes have been described, considerably expanding the synthetic scope of this powerful process which allows the resolution of racemic compounds with up to 100% yield. Today, a significant number of chiral organocatalysts are available that afford excellent levels of stereocontrol in various reactions evolving through DKR that could only previously be achieved using biocatalysts. The goal of the present review is to cover the works dealing with organocatalytic reactions evolving through DKR. This review is subdivided into four sections, according to the different types of organocatalysts employed in these reactions, such as Cinchona alkaloid catalysts, catalysts derived from amino acids, hydroxy acid catalysts, and miscellaneous organocatalysts. Abbreviations: Ac: acetyl; Ar: aryl; BINOL: 1,1′‐bi‐2‐naphthol; Bn: benzyl; Bu: butyl; c: cyclo; Cbz: benzyloxycarbonyl; CPME: cyclopentyl methyl ether; Cy: cyclohexyl; DABCO: 1,4‐diazabicyclo[2.2.2]octane; de: diastereomeric excess; DKR: dynamic kinetic resolution; DMF: dimethylformamide; Dmpe: 1,2‐bis(dimethylphosphino)‐ethane; DMSO: dimethyl sulfoxide; DYKAT: dynamic kinetic asymmetric transformation; ee: enantiomeric excess; Et: ethyl; Fmoc: 9‐fluorenylmethoxycarbonyl; Fu: furyl; Me: methyl; MTBE: methyl tert‐butyl ether; Naph: naphthyl; Pent: pentyl; Ph: phenyl; PMP: p‐methoxyphenyl; Pr: propyl; TBHP: tert‐butyl hydroperoxide; TEA: triethylamine; THF: tetrahydrofuran; Thio: thiophene; TMS: trimethylsilyl; Tol: tolyl.     

Combined Enzyme and Transition-Metal Catalysis for Dynamic Kinetic Resolutions

The preparation of optically pure alcohols, axially chiral allenes, and amine derivatives by using enzymes and transition-metal catalysts through dynamic kinetic resolution (DKR) is reviewed. After a general introduction into enzymatic kinetic resolutions and racemizations catalyzed by transition-metal complexes, selected examples of DKRs are presented, from early work to more recent outstanding contributions, and also applications of this approach.     

Heterogeneous Catalysts for Racemization and Dynamic Kinetic Resolution of Amines and Secondary Alcohols

This paper gives an overview of the available heterogeneous catalysts for racemization of chirally stable secondary alcohols and amines, and of the combination of these catalysts with immobilized enzymes in dynamic kinetic resolution (DKR) for production of enantiopure esters or amides. For the one-pot DKR process, compatibility of enzyme and heterogeneous catalyst is a major issue, and in some cases the combination fails because of (mutual) deactivation. Heterogeneous catalysts of various types, such as zeolites or oxides effect alcohol racemization; they function either via acid catalysis and carbenium chemistry, or via a redox pathway via the ketone. Dynamic kinetic resolution of aliphatic alcohols using a heterogeneous catalyst in mild conditions is however an open challenge. Heterogeneous amine racemization catalysts invariably operate using a redox mechanism via the imine. In this case, the scope encompasses benzylic and aliphatic amines. The practicality of the approach is illustrated with the production of enantiopure N-acylated homoserine lactones, which are signalling compounds in microbial communities.     

Heterogeneous Raney Nickel and Cobalt Catalysts for Racemization and Dynamic Kinetic Resolution of Amines

Raney metals were studied as heterogeneous catalysts for racemization and dynamic kinetic resolution (DKR) of chiral amines, as an alternative to metals like palladium or ruthenium. Both Raney nickel and cobalt were able to selectively racemize various chiral amines with high selectivity. In the racemization of benzylic primary amines, the minor formation of side products, e.g., secondary amines, can be suppressed by varying the hydrogen pressure. In the racemization of aliphatic amines over Raney catalysts, the selectivity is very high, with the enantiomeric amine as the sole product. DKR of racemic aliphatic amines can be performed with immobilized Candida antarctica lipase B and Raney nickel in one pot; for 2‐hexylamine, a yield of 95 % of the acetylated amide was achieved, with 97 % ee. Attention is devoted to the compatibility of the enzyme and the metal catalyst during the DKR. For benzylic primary amines, a two‐pot process is proposed in which the liquid is alternatingly shuttled between two vessels containing the solid racemization catalyst and the biocatalyst. After 4 such cycles, the amide of (R)‐1‐phenylethylamine was obtained with 94 % yield and more than 90 % ee.     

(2S,4E)-5-氯-2-异丙基-4-戊烯酸乙酯的简易合成

以异戊酸乙酯与(E)-1,3-二氯丙烯为原料,通过烷基化反应得到(±)-(4E)-5-氯-2-异丙基-4-戊烯酸乙酯,经猪肝酯酶催化(进行动力学拆分)得到纯阿利克仑(Aliskiren)中间体(2S,4E)-5-氯-2-异丙基-4-戊烯酸乙酯。通过回收拆分母液以88%的收率得到(2R,4E)-5-氯-2-异丙基-4-戊烯酸。该方法绿色环保,操作简洁易行,具有工业化应用前景。     

An Aminocaprolactam Racemase from Ochrobactrum anthropi with Promiscuous Amino Acid Ester Racemase Activity

The kinetic resolution of amino acid esters (AAEs) is a useful synthetic strategy for the preparation of single‐enantiomer amino acids. The development of an enzymatic dynamic kinetic resolution (DKR) process for AAEs, which would give a theoretical yield of 100 % of the enantiopure product, would require an amino acid ester racemase (AAER); however, no such enzyme has been described. We have identified low AAER activity of 15 U mg^?1 in a homologue of a PLP‐dependent α‐amino ?‐caprolactam racemase (ACLR) from Ochrobactrum anthropi. We have determined the structure of this enzyme, OaACLR, to a resolution of 1.87 Å and, by using structure‐guided saturation mutagenesis, in combination with a colorimetric screen for AAER activity, we have identified a mutant, L293C, in which the promiscuous AAER activity of this enzyme towards l ‐phenylalanine methyl ester is improved 3.7‐fold.