一种新颖海洋微生物酯酶的功能鉴定及其在D-乳酸甲酯制备中的应用（英文）

手性药物不同对映体往往表现出截然不同的生理活性和毒性,为了减少有毒副作用的对映体,并降低其生物活性,光学纯手性药物的合成一直是制药行业的研究热点.由于手性药物中间体是合成手性药物的重要构建模块,因此手性药物中间体的合成至关重要.手性乳酸及其酯是合成各类药物、农药和聚合物的重要中间体,在制药工业和材料工业中手性乳酸及其酯的制备非常重要.手性乳酸及其酯可以通过传统的有机化学合成和生物酶催化合成,通过有机化学合成法往往很难得到光学纯度较高的手性乳酸及其酯,而生物酶催化法可以得到光学纯的手性乳酸及其酯,同时避免了有机化学合成所导致的金属残留和环境污染等问题.生物酶法合成光学纯的乳酸及其酯可以通过脱氢酶不对称还原酮的前体得到,然而生物催化使用脱氢酶法需要价格昂贵的辅助因子,如NADH和NADPH.而另外一种生物催化方法是通过利用酯酶或者脂肪酶不对称水解外消旋的酯,从而得到光学纯度较高的手性中间体.目前市场上的L-乳酸甲酯价格不太昂贵,因为L-乳酸甲酯可以直接通过大发酵的方法取代有机化学法和酶法直接得到.然而D-乳酸甲酯不能使用廉价的发酵法直接得到,因而其价格昂贵.生物酶催化法可能会成为制备D-乳酸甲酯的主要方法,因为利用生物酶法可以得到光学纯度较高的D-乳酸甲酯.本文从西太平洋深海来源的微生物Pseudomonas oryzihabitans HUP022中克隆并异源表达了一种新颖酯酶PHE14.通过对酯酶PHE14的酶学性质鉴定表明,酯酶PHE14的最适反应底物为对硝基苯酚乙酸酯(C2),最适pH为9.0,最适温度为60°C.PHE14催化最适反应底物C2的活性达到293.07U/mg,Vmax和Km分别为200μM/(mg·min)和0.24mmol/L.酯酶PHE14对多种有机溶剂、表面活性剂和金属离子都具有非常好的耐受性.深海微生物酯酶PHE14对高浓度NaCl具有很好的耐受性,在4mol/LNaCl存在下,相对酶活力为71.4%.同时,酯酶PHE14能够催化消旋乳酸甲酯的不对称水解反应制备重要的手性化工产品—D-乳酸甲酯.与先前的一些酯酶拆分的报道不同,有机溶剂和表面活性剂对酯酶PHE14催化的动力学水解反应没有促进作用.而且,本研究是首次通过酶动力学水解拆分反应制备光学纯的D-乳酸甲酯.经过实验优化,在pH9.0和30°C的条件下,反应产物D-乳酸甲酯的对映体过量值和产率分别为99%和88.7%.深海微生物酯酶PHE14作为一种绿色生物催化剂,在多种工业的不对称合成中都具有非常好的应用潜力.     

基于醋酸铑、磺酸和手性亚磺酰胺基脲共催化的α-重氮酯与酰胺不对称N—H插入反应研究

研究了醋酸铑[Rh2(OAc)4]、手性亚磺酰胺基脲和非手性磺酸共催化的α-重氮酯与酰胺化合物的不对称N—H插入反应.研究发现α-重氮酯在醋酸铑催化下形成金属卡宾,该金属卡宾与酰胺反应生成潜手性活泼叶立德中间体.在催化剂量的手性亚磺酰胺基脲和非手性磺酸存在下,潜手性叶立德中间体发生不对称质子化,合成了手性α-氨基酸衍生物.反应过程中,手性亚磺酰胺基脲和非手性磺酸作为"手性质子梭"催化不对称质子迁移从而实现了反应的对映选择性控制.该方法发展了非手性铑、手性亚磺酰胺基脲和非手性磺酸不对称共催化体系,为合成α-氨基酸衍生物提供了一种新途径,反应收率最高可达84%,对映选择性最高可达77%.     

SpinPHOX/Ir(Ⅰ)催化的2-羟甲基-3-芳基丙烯酸的不对称氢化

光学活性的2-羟甲基-3-芳基丙酸类化合物是许多手性药物的关键合成中间体,但到目前为止其不对称合成方法大多存在对映选择性不高及/或底物范围有限等问题.报道了手性SpinPHOX/Ir(I)络合物在一系列2-羟甲基-3-芳基丙烯酸的不对称氢化中表现出优良的催化性能,取得完全的底物转化和良好到优秀的对映选择性(高达95%ee).对于同一2-羟甲基-3-芳基丙烯酸底物的不对称氢化,使用中心手性相同但螺环骨架上的轴手性相反的催化剂分别以优良的对映选择性获得构型相反的产物,从而为光学活性2-羟甲基-3-芳基丙酸及相关手性药物的不对称合成提供了一条简便高效的途径.     

一个新颖南极微生物酯酶EST112-2的功能鉴定和在手性叔醇(S)-芳樟醇制备中的应用（英文）

手性叔醇是合成药物和一些香料产品的非常重要中间体.芳樟醇是叔醇的一种,不同构型的芳樟醇具有不同的香气.因此如何研发合适的制备方法以获得高光学纯度的芳樟醇等叔醇是急需解决的技术问题.生物酶催化合成符合绿色化学的理念,但是由于叔醇化学结构中的空间位阻影响,使用生物酶催化的拆分反应制备高光学纯度的叔醇比较困难.对来自南极微生物的一个新的酯酶EST112-2进行了功能鉴定,并将其作为合成手性芳樟醇的生物催化剂.EST112-2可以通过不对称水解乙酸芳樟酯获得(S)-芳樟醇.对反应的p H、温度、共溶剂、底物浓度、催化剂用量以及反应时间等参数进行优化,EST112-2制备的(S)-芳樟醇的光学纯度大于66%,得率超过72%.EST112-2制备的(S)-芳樟醇的光学纯度要远远高于以往报道.     

5-羟基色胺受体激动剂(1R,2S)-(-)-2-(2-羟基苯基)-N,N-二丙基环丙胺的不对称合成

利用手性双唑啉与三氟甲磺酸亚铜催化2-甲氧基苯乙烯与重氮乙酸二环己基甲酯的不对称环丙烷化反应合成了手性环丙烷羧酸酯,用氢氧化钠对其进行选择性水解得到全反式环丙烷羧酸,其ee值经GC测定为88%.进一步经过Curtius重排、烷基化等反应及重结晶等步骤合成了光学纯的具有生理活性的环丙胺化合物1a和1b.     

不对称活化催化亚胺和乙基锌加成反应

手性含氮化合物是许多药物的重要中间体,因此对光学纯的含氮化合物的合成研究一直是有机化学和药物化学研究的热点.亚胺作为一类重要的前体化合物得到了广泛的应用,亚胺的不对称还原,烯丙基化,Mannich、Strcker,Aza Diels-Alder等反应都是合成光学纯含氮化合物的有效方法.其中亚胺与有机锌试剂的不对称加成反应是合成手性胺的简便方法之一,近年来得到了很大的发展[1].     

手性芳基醇的生物催化不对称合成

光学活性芳基醇化合物是一类重要的手性砌块,可用于合成多种手性药物,其制备技术研究是近年来的研究热点。与传统的化学制备方法相比,生物催化方法由于具有选择性高、反应条件温和以及环境危害少等优点更具吸引力。通过生物催化不对称还原芳基酮是合成对映体纯芳基醇最有效的方法之一。本文综述了生物催化不对称还原制备手性芳基醇的研究进展,重点介绍了不同形式的生物催化剂应用于生物不对称还原的研究现状,包括微生物细胞、酶、重组工程菌以及固定化细胞等,概述了有机溶剂、表面活性剂和离子液体等底物助溶剂对生物不对称催化的影响,并对生物催化制备对映体纯芳基醇的研究前景进行了展望。     

铑和手性螺环磷酸协同催化α-芳基重氮酮对醇的O-H键的不对称插入反应

过渡金属催化卡宾对O-H键的不对称插入反应是合成手性醇及其衍生物的直接方法.近年来,人们发展了多种手性催化剂实现了重氮酯衍生的金属卡宾对醇、酚、羧酸甚至水的O-H键的高对映选择性插入反应,但是重氮酮作为卡宾前体的不对称O-H键插入反应鲜有成功的例子.以非手性双铑络合物和手性螺环磷酸组成的协同催化体系,首次实现了α-重氮酮对醇的O-H键的不对称插入反应,获得了较高的收率和高达95%ee的对映选择性.反应为手性α-烷氧基酮这类重要手性化合物提供了高效的合成方法.还通过密度泛函理论计算,对反应机理进行了初步研究,发现水很可能参与了手性磷酸促进的烯醇中间体质子转移过程.     

通过不对称多组分反应高效构建手性磺酰胺类化合物

手性磺酰胺类化合物在新型药物方面研究中占据越来越重要的地位.我们成功地实现了磺酰胺、芳基重氮乙酸酯以及亚胺的不对称三组分反应.此反应给出了高达85%产率,以及优异的非对映选择性（d.r.>20：1）和对映选择性（最高可达99%ee）,为高效构建具有两个手性碳的光学纯磺酰胺类化合物提供了一种快速合成方法.我们将反应放大到了克级规模,并对三组分产物进一步衍生得到一种具有三个手性中心的光学纯含亚砜亚胺骨架的五元环化合物.反应的选择性通过过渡金属与手性磷酸协同催化控制.     

R-沙美特罗的合成方法

近年来手性沙美特罗的合成方法有微生物催化、不对称氢化、CBS(Corey-Bakshi-Shibata)还原反应及不对称Henry反应、手性(Salen)Co试剂催化的HKR(末端环氧不对称水解动力学)拆分反应等。对这些方法进行比较,结果表明,不对称催化合成由于其反应收率高、反应产物光学纯度高、操作容易控制,在目前手性药物的合成中处于主导地位。此外酶催化不对称合成、手性辅基诱导的对映选择性合成等方法也是有效的途径。     

Sharpless Asymmetric Aminohydroxylation: Scope,Limitations, and Use in Synthesis

As a valuable methodology for organic synthesis , asymmetric aminohydroxylation (AA)—the catalytic and asymmetric conversion of alkenes into enantiomerically enriched N‐protected amino alcohols—has become established in a remarkably short period of time. Examples of the types of products that can be synthesized easily on a reasonably large scale and in enantiomerically pure form are shown in the picture.     

Development of a practical mass spectrometry based assay for determining enantiomeric excess. A fast and convenient method for the optimization of PLE-catalyzed hydrolysis of prochiral disubstituted malonates

A practical mass spectrometry-based enantioselectivity assay is presented which makes use of enantiomerically enriched, but not enantiomerically pure, probe molecules readily obtained from esterase hydrolysis of prochiral malonates. The technique presented here allows us to recycle materials obtained from esterase hydrolysis which give substantial, but synthetically insufficient, enantiomeric excess as probe molecules in an enantioselectivity assay. The enantiomerically enriched products are esterified using deuterium-labelled alcohol. The enantiomeric excess is measured using mass spectrometry (LC–MS and LDI) by measuring the D₅/H₅ ratio in the resulting products obtained from an enzymatic hydrolysis. The D₅/H₅ ratio is corrected to account for the enantiomeric purity of the probe. Herein we report the results obtained from Pig Liver Esterase hydrolyses of prochiral malonate esters and outline the strengths and limitations of this approach to enantioselectivity determinations. This assay strategy was able to identify reaction conditions that led to an improvement in ee from 70% ee to >97% ee in the PLE-catalyzed hydrolysis of a prochiral malonate used to prepare unnatural serine analogues.     

Functional Characterization of a Marine <Emphasis Type="Italic">Bacillus</Emphasis> Esterase and its Utilization in the Stereo-Selective Production of D-Methyl Lactate

Chiral lactic acid and its ester derivatives are crucial building blocks and platforms in the generation of high value-added drugs, fine chemicals and functional materials. Optically pure D-lactic acid and its ester derivatives cannot be directly generated from fermentation and are quite expensive. Herein, we identified, heterologously expressed and functionally characterized one Bacillus esterase BSE01701 from the deep sea of the Indian Ocean. Esterase BSE01701 could enzymatically resolve inexpensive racemic methyl lactate and generate chiral D-methyl lactate. The enantiomeric excess of desired chiral D-methyl lactate and the substrate conversion could reach over 99 % and 60 %, respectively, after process optimization. Notably, the addition of 60 % (v/v) organic co-solvent heptane could greatly improve both the enantiomeric excess of D-methyl lactate and the conversion. BSE01701 was a very promising marine microbial esterase in the generation of chiral chemicals in industry.     

Selector‐Induced Dynamic Deracemization of a Selectand‐Modified Tropos BIPHEPO‐Ligand: Application in the Organocatalyzed Asymmetric Double‐Aldol‐Reaction

Stereolabile interconverting catalysts open up the possibility of directing enantioselectivity in asymmetric synthesis by formation of diastereomeric complexes with chiral auxiliaries and deracemization. However, the stoichiometrically used auxilliaries can significantly limit the potential applications of such systems. We synthesized a new BIPHEPO tropos ligand containing achiral selectands in the backbone, which forms transient diastereomeric associates with amylose‐tris‐3,5‐dimethylphenyl carbamate as a selector and thus deracemizes. The enantiomerically enriched BIPHEPO obtained was successfully used in the organocatalytic asymmetric double aldol addition of substituted methyl ketones to form benzaldehyde. This strategy combines an on‐column deracemization with the high stereoinduction of chiral biarylphosphineoxides and opens up new possibilities in the field of self‐amplified asymmetric syntheses.     

Enantioselective synthesis of indolizidine alkaloid trans-209D

(S)-N-Boc-baikiain, readily accessible from enantiomerically enriched 2,3-epoxy-5-hexen-1-ol 4 (prepared by Sharpless asymmetric epoxidation), was used as the starting material in the synthesis of indolizidine alkaloid trans-209D , which was obtained in 13 steps and 14% yield from 1 (5% from 4).     

Enantioselective Diels-Alder approach to C-3-oxygenated angucyclinones from (SS)-2-(p-tolysulfinyl)-1,4-naphthoquinone

Chiral racemic vinylcyclohexenes 2, bearing oxygenated substituents and/or a methyl group at the C-5 position of the cyclohexene ring, were submitted to Diels-Alder reactions with enantiomerically pure (SS)-(2-p-tolylsulfinyl)-1,4-naphthoquinone [(+)-1]. The domino cycloaddition/pyrolytic sulfoxide elimination process led to the formation of enantiomerically enriched angularly tetracyclic quinones anti-6 and syn-7, which were obtained from the kinetic resolution of the racemic diene. In all cases, (SS)-(2-p-tolylsulfinyl)-1,4-naphthoquinone reacted from the less hindered face of the more reactive s-cis conformation, to form products in good enantiomeric excesses. Steric effects and torsional interactions in the corresponding approaches account for the observed pi-facial diastereoselectivities at both partners. The usefulness of this methodology is illustrated with the four-step totally asymmetric synthesis of the C-3-oxygenated angucyclinone derivative (-)-8-deoxytetrangomycin 10 in 26% overall yield and with 50% enantiomeric purity.     

Catalytic enantioselective synthesis of axially chiral allenes

The conventional procedures for preparing optically active axially chiral allenes generally require stoichiometric chiral sources as either substrates or reagents. On the other hand, examples of catalytic asymmetric synthesis of axially chiral allenes are rare and it is a relatively underdeveloped area in synthetic organic chemistry. In this review article, various methods for preparing enantiomerically enriched axially chiral allenes using substoichiometric chiral sources are surveyed. Some reactions with stoichiometric but recoverable chiral sources are also mentioned. Most of the asymmetric reactions in these categories are transition-metal-catalyzed reactions, and there are a few examples of organocatalytic reactions. In addition, some enzymatic/microbial systems are also known.     

Enzyme mediated kinetic resolution of δ-hydroxy-α,β-unsaturated esters as a route to optically active δ-lactones

A novel synthetic route to optically active saturated and unsaturated δ-lactones based on enzymatic kinetic resolution and ring-closing metathesis reactions has been proposed. The influence of temperature, co-solvent, organic additives and the substrate structure on the catalytic behavior of selected hydrolases was studied. The substantial impact of the organic co-solvent and surfactant type on the enzymatic activity and enantioselectivity was observed providing enantiomerically pure δ-hydroxy-α,β-unsaturated esters. The established protocol combining enzymatic kinetic resolution with ring closing metathesis was successfully applied in the synthesis of the enantiomerically pure (6R)-phenyl-5,6-dihydro-2H-pyran-2-one which plays crucial role in the synthesis of the number of bioactive compounds.     

Studies on the chemoenzymatic synthesis of 3-phenyl-GABA and 4-phenyl-pyrrolid-2-one: the influence of donor of the alkoxy group on enantioselective esterification

A new chemoenzymatic method for the synthesis of enantiomerically pure 3-phenyl-γ-aminobutyric acid 1 and 4-phenyl-pyrrolid-2-one 9 based on the enzymatic kinetic resolution of 3-phenyl-4-pentenoic acid 2 is described herein. Enzymatic resolution of the racemic substrate provided products with good enantioselectivity upon esterification. In these reactions, a new class of alkoxy group donor—orthoesters, acetals and ketals were used. The best results of the enzymatic kinetic resolution were obtained for triethyl orthoacetate in toluene solvent.     

Alternative approach to the synthesis of optically active β-keto sulfoxides by furylhydroperoxides enantioselective oxidations

Enantiomerically enriched β-keto sulfoxides are obtainable by an alternative method to the classical reaction of the enantiomerically pure α-sulfinyl anion with esters or by Andersen's synthesis, through Sharpless modified kinetic resolution of racemic β-keto sulfoxides. High e.e.s are achieved by combining asymmetric oxidation and kinetic resolution using furylhydroperoxides as oxidants.