非酶催化动力学拆分的研究进展

动力学拆分是合成光学纯化合物的重要方法之一. 在酶催化的动力学拆分取得进展的同时, 近几年有关非酶催化的动力学拆分正在成为人们研究的热点, 主要拆分反应涉及对映选择性的酰化、氧化、还原、开环、成环、取代和加成等反应, 对该领域的最新研究进展进行了简要综述.     

路易斯酸碱催化的外消旋体(动态)动力学拆分反应

外消旋体的(动态)动力学拆分反应是制备手性化合物的重要方法之一.反应可以通过酶催化或非酶催化的手段来实现,也可以通过两种方法的有机结合来进行.在非酶催化反应中,路易斯酸碱催化是比较常用的方法,它们被广泛地用于多种外消旋体的(动态)动力学拆分反应中,目前在该领域取得了很大的进展.本文讨论了路易斯酸及路易斯碱催化体系在外消旋体(动态)动力学拆分反应中应用的最新进展.     

酶催化不对称还原和消旋动力学拆分及其在合成上的应用

最近,酶催化不对称还原反应和消旋动力学拆分,在合成光学活性物质的方法上,有较大进展,有些反应已有实用价值。酶催化反应中,所用的酶往往直接利用生物体本身,来源方便,价格低廉,操作简便。目前,在酶催化反应中,以羰基的不对称还原应用最广。与此有关的酶催化消旋动力学拆分的研究也日益增多。本文对这两方面的最新研究情况作一简要介绍。     

叔醇的动力学拆分研究进展

手性叔醇结构广泛存在于生物活性物质、天然产物和药物分子中,实现其高效不对称催化合成具有重要意义.消旋醇的动力学拆分是一种合成高光学纯度手性醇的重要方法,然而由于叔醇α-碳上带三个不同的非氢取代基团,手性识别难度较大,因而发展高效且具有广泛底物适用性的叔醇动力学拆分方法具有较大的挑战.尽管如此,近年来非酶催化的叔醇的动力学拆分领域取得了快速的发展,一些新颖的不对称催化反应、催化体系被成功应用于叔醇的动力学拆分反应中.对叔醇动力学拆分反应进行了系统总结,分类介绍了这些反应的底物适用性、特点、机理以及局限等,并对该领域的未来发展进行展望.     

有机相中的酶促拆分过程

总结了有机溶剂中的酶催化研究进展, 讨论了影响有机溶剂中酶促不对称转化过程对映体选择性的因素和拆分动力学。     

酶法动力学拆分制备光学活性γ-内酯

研究了脂肪酶对桃醛和γ-癸内酯的水解动力学拆分反应,考察了温度、pH值、酶的用量等因素对酶催化水解拆分过程的影响.选择氯化钙-阿拉伯胶水溶液作为反应介质,使γ-内酯拆分产物取得较高的ee值.回收拆分中产生的γ-羟基酸,外消旋化后再内酯化,投入下一批反应,提高了光学活性γ-内酯的总得率.     

金属-生物酶共催化合成手性化合物的研究进展

综述了金属-生物酶共催化合成手性化合物的研究进展,重点介绍了金属-生物酶共催化在动态动力学拆分、串联反应和"一锅法"一步反应中的应用,并对其未来发展进行了展望。参考文献49篇。     

新型酰基供体用于酶法动力学拆分制备(R)-1-(2-萘基)乙胺的研究

首次成功实现了光学纯(R)-1-(2-萘基)乙胺的高效酶法动力学拆分制备,考察了脂肪酶种类、溶剂、酰基供体、底物浓度、反应温度等对拆分效果的影响,发现新型酰基供体——正戊酸对氯苯酯能够很好地抑制非酶促自催化酰胺化效应.在甲苯溶剂中,底物浓度300 mmol/L,40℃条件下,采用该供体在脂肪酶Novozym 435催化下,动力学拆分反应8 h转化率达到理论最佳值50%,eep>99%.     

β-氨基酸合成研究进展

综述了合成β-氨基酸的五种主要方法,包括化学拆分、手性色谱柱拆分、Arndt-Eistert反应、不对称合成和酶催化合成的最新研究进展,特别是近年来发展迅速的不对称合成和酶催化合成。参考文献90篇。     

脂肪酶催化二次动力学拆分制备高光学纯度(S)-萘普生

设计了一种利用立体选择性相反的两种脂肪酶催化二次动力学拆分,由外消旋萘普生甲酯制备高光学纯度(S)-萘普生的方法。理论曲线预测,与简单的酶促动力学拆分反应相比,二次动力学拆分可以明显提高高光学纯度产物的产率.根据几种脂肪酶在微水/异辛烷双液相反应体系中不对称水解萘普生甲酯的立体选择性和对映体比率(E),首先选用R选择性的固定化南极假丝酵母脂肪酶(Novozym 435)对外消旋萘普生甲酯进行第一次拆分,然后选用S选择性的柱状假丝酵母脂肪酶(CRL)对S过量的剩余底物萘普生甲酯在同样的反应体系中进行第二次拆分.该二次拆分反应对映体过量值为96.8%的(S)-萘普生产率达19.9%.     

Kinetic resolution and chemoenzymatic dynamic kinetic resolution of functionalized gamma-hydroxy amides

[reaction: see text] An efficient kinetic resolution of racemic gamma-hydroxy amides 1 was performed via Pseudomas cepacia lipase (PS-C)-catalyzed transesterification. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity (E values of up to >250). The combination of enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution. The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution yields the corresponding acetates in good yield and good to high enantioselectivity (ee's up to 98%). The synthetic utility of this procedure was illustrated by the practical synthesis of the versatile intermediate gamma-lactone (R)-5-methyltetrahydrofuran-2-one.     

An efficient route to chiral alpha- and beta-hydroxyalkanephosphonates

Enzymatic kinetic resolution of alpha- and beta-hydroxyphosphonates in combination with ruthenium-catalyzed alcohol isomerization led to a successful dynamic kinetic resolution. A variety of racemic hydroxyphosphonates were efficiently transformed to the corresponding enantiomerically pure acetates (ee up to 99% and yield up to 87%).     

Dynamic kinetic resolution via dual-function catalysis of modified cinchona alkaloids: asymmetric synthesis of alpha-hydroxy carboxylic acids

A highly enantioselective catalytic transformation of racemic alpha-hydroxy acids to optically active alpha-hydroxy acids is reported. A new procedure was developed for the condensation of racemic alpha-hydroxy acids with trichloromethyl chloroformate (diphosgene) at room temperature in the presence of activated charcoal to form 5-substituted-1,3-dioxolane-2,4-diones in 90-100% yield. An efficient dynamic kinetic resolution of 5-aryl dioxolanediones was realized via a modified cinchona alkaloid-catalyzed alcoholytic opening of the dioxolanedione ring, generating a variety of optically active alpha-hydroxy esters in 91-96% ee and 61-85% chemical yield. In this dynamic kinetic resolution, the modified cinchona alkaloid was found to serve dual catalytic roles, mediating both the rapid racemization of the 5-aryl dioxolanediones and the enantioselective alcoholytic ring opening of the 5-aryl dioxolanediones. Consequently, both enantiomers of the 5-aryl dioxolanediones were converted to highly enantiomerically enriched aromatic alpha-hydroxy esters in yields (61-85%), far exceeding the maximum of 50% for a normal kinetic resolution. This development not only represents an expansion of the scope of asymmetric acyl-transfer catalysis of synthetic catalysts but also provides a new approach for the development of efficient chemical dynamic kinetic resolutions promoted by a single catalyst. 5-Alkyl dioxolanediones were resolved by a conventional but highly enantioselective kinetic resolution to provide alpha-hydroxy acids and esters in high optical purity and good yields.     

Study on the Non-enzymic Catalytic Enantioselective Methanolysis of 4-benzyl-2-phenyl-5(4H)-oxazolone

Dynamic-kinetic resolution is different from kinetic resolution¹. In ideal case,dynamic-kinetic resolution can convert racemic substrate to product with 100% yield and >99% e.e. whereas kinetic resolution can only converted racemic substrate to enantiomeric pure product with 50% yield.     

Development of a rapid,room-temperature dynamic kinetic resolution for efficient asymmetric synthesis of alpha-aryl amino acids

[reaction: see text] A rapid, highly efficient and general dynamic kinetic resolution (DKR) of racemic alpha-aryl UNCAs with the dual-function catalysis of modified cinchona alkaloid was accomplished at room temperature. This DKR led to the development of a highly enantioselective catalytic method for the practical synthesis of a wide range of alpha-aryl and alpha-heteroaryl amino acids in 89-92% ee and 86-95% yield from racemic UNCAs.     

Dynamic kinetic resolution of allylic alcohols mediated by ruthenium- and lipase-based catalysts

An enzyme-metal combo reaction has been developed for the dynamic kinetic resolution of allylic alcohols in which racemic substrates are transformed by a lipase and a ruthenium complex in the presence of an acyl donor to allylic acetates of high optical purity in over 80% yield.     

Oxidative kinetic resolution of racemic alcohols catalyzed by chiral ferrocenyloxazolinylphosphine-ruthenium complexes

Oxidative kinetic resolution of racemic secondary alcohols by using acetone as a hydrogen acceptor in the presence of a catalytic amount of [RuCl(2)(PPh(3))(ferrocenyloxazolinylphosphine)] (2) proceeds effectively to recover the corresponding alcohols in high yields with an excellent enantioselectivity. When 1-indanol is employed as a racemic alcohol, the oxidation proceeds quite smoothly even in the presence of 0.0025 mol % of the catalyst 2 to give an optically active 1-indanol in good yield with high enantioselectivity (up to 94% ee), where turnover frequency (TOF) exceeds 80,000 h(-1). From a practical viewpoint, the kinetic resolution is investigated in a large scale, optically pure (S)-1-indanol (75 g, 56% yield, >99% ee) being obtained from racemic 1-indanol (134 g) by employing this kinetic resolution method twice.     

Dynamic kinetic resolution via asymmetric conjugate reduction: enantio- and diastereoselective synthesis of 2,4-dialkyl cyclopentanones

Herein, we report the kinetic and the dynamic kinetic resolutions of racemic 3,5-dialkyl-2-cyclopenten-1-ones. Kinetic resolution, with good selectivity factors (25-52), was achieved by conjugate reduction with catalytic CuCl/NaOt-Bu/(S)-p-tol-BINAP and stoichiometric quantities of poly(methylhydrosiloxane) (PMHS). When stoichiometric amounts of NaOt-Bu and t-BuOH were included in the reaction mixture, rapid racemization of the starting material occurred allowing for the dynamic kinetic resolution of the cyclopentenone substrates. In this process, chiral 2,4-dialkylcyclopentanones were isolated with high stereoselectivity (ee > or = 91%, dr > or = 90:10) and in high yield (> or =89%).     

Dynamic kinetic resolution of racemic tropic acid ethyl ester and its derivatives

The dynamic kinetic resolution of racemic mixtures of tropic acid ethyl ester under substrate racemizing conditions was studied using lipase PS with a ruthenium catalyst. Isopropenyl acetate was used as an acyl donor, since it was found to be compatible with both catalysts; this resulted in an efficient dynamic kinetic resolution. With this process, a variety of racemic tropic acid ethyl esters were transformed to optically active acetoxy-2-arylpropionic acid ethyl esters with 60-88% yields and 53-92% ee.     

Phosphine-catalyzed regiospecific allylic amination and dynamic kinetic resolution of Morita-Baylis-Hillman acetates

Exposure of Morita-Baylis-Hillman (MBH) acetates to tertiary phosphine catalysts in the presence of 4,5-dichlorophthalimide enables regiospecific allylic substitution through a tandem S(N)2'-S(N)2' mechanism. Through the use of the chiral phosphine catalyst (R)-Cl-MeO-BIPHEP, chiral racemic MBH acetate 4 is converted to the corresponding allylic amination product in 80% yield and 56% enantiomeric excess, thus establishing the feasibility of dynamic kinetic resolution. [reaction: see text]