共查询到20条相似文献,搜索用时 609 毫秒
1.
Jianheng Ye Chao Wang Lin Chen Xinjun Wu Li Zhou Jian Sun 《Advanced Synthesis \u0026amp; Catalysis》2016,358(7):1042-1047
Catalytic asymmetric reduction of N‐unsubstituted β‐enamino esters represents a major challenge for asymmetric catalysis. In this paper, the first organocatalytic system that could be used for the asymmetric hydrosilylation of N‐unsubstituted β‐enamino esters has been developed. Using N‐tert‐butylsulfinyl‐L ‐proline‐derived amides and L ‐pipecolinic acid‐derived formamides as catalyst, a broad range of β‐aryl‐ and β‐alkyl‐substituted free β‐amino esters could be prepared with high yields and enantioselectivities. The practicality was illustrated by the gram‐scale asymmetric synthesis of ethyl (R)‐3‐amino‐3‐phenylpropanoate and isopropyl (S)‐3‐amino‐4‐(2,3,5‐trifluorophenyl)butanoate. The resulting product can be smoothly transformed to the FDA approved medicines dapoxetine and sitagliptin in a short synthetic route.
2.
Eleonora Gianolio Resmi Mohan Albrecht Berkessel 《Advanced Synthesis \u0026amp; Catalysis》2016,358(1):30-33
The dynamic kinetic resolution of α‐substituted racemic β‐lactams by alcoholytic ring‐opening, catalyzed by immobilized lipase B from Candida antarctica is described. With this process, a variety of racemic α‐substituted N‐Cbz‐azetidinones (Cbz=benzyloxycarbonyl) was transformed to the corresponding N‐Cbz‐protected β2‐amino acid allyl esters with high enantioselectivity (up to 99%) and high yields (up to quantitative) at room temperature.
3.
Tobias Heck Dieter Seebach Prof. Dr. Steffen Osswald Dr. Matthijs K. J. ter Wiel Dr. Hans‐Peter E. Kohler Dr. Birgit Geueke Dr. 《Chembiochem : a European journal of chemical biology》2009,10(9):1558-1561
Access to enantiopure β‐amino acids : β‐Aminopeptidases are hydrolases that possess the unique ability to cleave N‐terminal β‐amino acids from peptides and amides. Hydrolysis of racemic β‐amino acid amides catalyzed by these enzymes displays enantioselectivity with strong preference for substrates with the L ‐configuration, and gives access to various aliphatic β‐amino acids of high enantiopurity.
4.
Yakun Wang Hang Yin Hai Qing Jingnan Zhao Yufeng Wu Qingwei Meng 《Advanced Synthesis \u0026amp; Catalysis》2016,358(5):737-745
The highly catalytic asymmetric α‐hydroxylation of β‐indanone esters and β‐indanone amides using peroxide as the oxidant was realized with a new C‐2′ substituted Cinchona alkaloid derivatives. The two enantiomers of α‐hydroxy‐β‐indanone esters could be obtained by simply changing the oxidant. This protocol allows a convenient access to the corresponding α‐hydroxy‐β‐indanone esters and α‐hydroxy‐β‐indanone amides with up to 99% yield and 98% ee.
5.
Yosuke Sumida Sachio Iwai Yoshiaki Nishiya Shinya Kumagai Toshihide Yamada Masayuki Azuma 《Advanced Synthesis \u0026amp; Catalysis》2016,358(13):2041-2046
Chiral amino acids are important intermediates for the pharmaceutical industry. We have developed a novel one‐pot enzymatic method for D ‐amino acid synthesis by the dynamic kinetic resolution of N‐succinyl‐dl ‐amino acids using D ‐succinylase (DSA) and N‐succinylamino acid racemase (NSAR, EC 4.2.1.113). The DSA from Cupriavidus sp. P4‐10‐C, which hydrolyzes N‐succinyl‐D ‐amino acids enantioselectively to their corresponding D ‐amino acids, was identified for the first time by screening soil microorganisms. Subsequently, the DSA gene was cloned and overexpressed in Escherichia coli. DSA was shown to comprise two subunits with molecular masses of 26 kDa and 60 kDa. Additionally, the NSAR gene from Geobacillus stearothermphilus NCA1503, which racemizes N‐succinylamino acids, was also cloned and overexpressed in E. coli. The highly purified DSA and NSAR prepared from each recombinant E. coli were characterized and used for D ‐amino acid synthesis. A one‐pot enzymatic method converted 100 mM N‐succinyl‐dl ‐phenylalanine to D ‐phenylalanine in 91.1% conversion with 86.7% ee. This novel enzymatic method may be useful for the industrial production of many D ‐amino acids.
6.
α‐Substituted β‐acetyl amides could undergo C C bond cleavage to form α‐keto amides when treated with copper(II) chloride (CuCl2) and boron trifluoride diethyl etherate (BF3⋅OEt2) under an oxygen atmosphere. The yield can be increased by the addition of tert‐butyl hydroperoxide which alone can also effect the reaction. The reaction provides a new protocol for the synthesis of α‐keto amides.
7.
Joanna Hejmanowska Anna Albrecht Jakub Pita ukasz Albrecht 《Advanced Synthesis \u0026amp; Catalysis》2015,357(18):3843-3848
An organocatalytic approach for the stereoselective synthesis of 3,4‐dihydrocoumarins with an α,α‐disubstituted amino acid moiety incorporated is presented. The developed methodology is based on the cascade reaction between α‐substituted azlactones and 2‐hydroxychalcones. It is initiated by a chiral Brønsted base‐catalyzed enantio‐ and diastereoselective Michael reaction followed by the azlactone ring opening to construct a 3,4‐dihydrocoumarin framework. Products bearing two adjacent stereogenic centers, one being quaternary, were formed with high enantioselectivities and excellent diastereoselectivities. Furthermore, the complete regioselectivity of the new cascade reactivity is worthy of notice.
8.
Ligand‐Free Nickel‐Catalysed 1,4‐Addition of Arylboronic Acids to α,β‐Unsaturated Carbonyl Compounds
Wen Chen Lu Sun Xi Huang Jiayi Wang Yanqing Peng Gonghua Song 《Advanced Synthesis \u0026amp; Catalysis》2015,357(7):1474-1482
A simple and efficient ligand‐free nickel‐based catalytic system has been developed for the 1,4‐addition of arylboronic acids to α,β‐unsaturated carbonyl compounds. With catalyst loadings of 1–2 mol%, a series of 1,4‐adducts from chalcones and cinnamates was obtained in moderate to excellent yields within 5–30 min under a nitrogen atmosphere and microwave irradiation. The 1,4‐addition of arylboronic acids to acrylates is less efficient.
9.
Krishna Bahadur SomaiMagar Yong Rok Lee 《Advanced Synthesis \u0026amp; Catalysis》2014,356(16):3422-3432
Efficient one‐step syntheses of α,β‐ and β,β‐dihaloenones were achieved by ruthenium(II)‐catalyzed reactions between cyclic or acyclic diazodicarbonyl compounds and oxalyl chloride or oxalyl bromide in moderate to good yields. This methodology offers several significant advantages, which include ease of handling, mild reaction conditions, one‐step reaction, and the use of an effective and non‐toxic catalyst. The synthesized compounds were further transformed into highly functionalized novel molecules bearing aromatic rings on the enone moiety using the Suzuki reaction.
10.
Xiang Li Siyu Li Suyan Sun Fan Yang Weiguo Zhu Yu Zhu Yusheng Wu Yangjie Wu 《Advanced Synthesis \u0026amp; Catalysis》2016,358(10):1699-1704
An efficient and generally applicable protocol for decarboxylative coupling of α,α‐difluoroarylacetic acids with ethynylbenziodoxolone (EBX) reagents has been developed, affording α,α‐difluoromethylated alkynes bearing various functional groups in moderate to excellent yields. Remarkably, this potassium persulfate (K2S2O8)‐promoted reaction employs water as solvent under transition metal‐free conditions, thus providing a green synthetic approach to α,α‐difluoromethylated alkynes.
11.
Wen‐Ting Wei Ren‐Jie Song Jin‐Heng Li 《Advanced Synthesis \u0026amp; Catalysis》2014,356(8):1703-1707
A novel copper‐catalyzed oxidative alkylation of α‐amino carbonyl compounds with ethers has been established for the selective synthesis of α‐etherized α‐amino carbonyl compounds. This oxidative alkylation is achieved by dual C(sp3) H bond oxidative cross‐coupling, and its scope is expanded to α‐amino ketones, α‐amino esters and α‐amino amides.
12.
An intramolecular imination/azidation sequence has been realized through the tetrakis(acetonitrile)copper(I) hexafluorophophate [Cu(CH3CN)4PF6]‐catalyzed reaction of γ,δ‐unsaturated ketone O‐benzoyl oximes with trimethylsilyl azide (TMSN3). The reaction proceeds via the copper‐mediated N O cleavage and subsequent C N forming 5‐exo cyclization. The thus formed intermediate is then azidated to afford the corresponding dihydropyrrole product. Preliminary mechanistic investigations suggest that the cyclization step does not involve a radical intermediate.
13.
This paper describes the aerobic oxidation of styrenes catalyzed by iron(III) chloride (FeCl3) to form β‐keto‐N‐alkoxyphthalimides in fair to good yields. This oxidative process employs mild conditions with green and atom efficient dioxygen (O2) as the oxidant.
14.
Cheonhyoung Park Min Woo Ha Byungsoo Kim Suckchang Hong Doyoung Kim Yohan Park Mi‐hyun Kim Jae Kyun Lee Jeeyeon Lee Hyeung‐geun Park 《Advanced Synthesis \u0026amp; Catalysis》2015,357(13):2841-2848
A new enantioselective synthetic method for the synthesis of α,α‐dialkylmalonates with a quaternary carbon center was developed via α‐alkylation of prochiral malonates by phase‐transfer catalysis (PTC). Asymmetric α‐alkylation of benzylideneamino tert‐butyl α‐methylmalonates under phase‐transfer catalytic conditions in the presence of (S,S)‐3,4,5‐trifluorophenyl‐NAS bromide afforded the corresponding α,α‐dialkylmalonates in high yields (up to 97%) with excellent enantioselectivities (up to 98% ee). The products were then selectively hydrolyzed to chiral malonic monoacids under basic, acidic, or catalytic hydrogenation conditions.
15.
Khushbu Kushwaha Balazs Pinter Syeda A. Shehzadi Chandi C. Malakar Christophe M. L. VandeVelde Frank deProft Kourosch AbbaspourTehrani 《Advanced Synthesis \u0026amp; Catalysis》2016,358(1):41-49
The metal‐free reaction of terminal arylacetylenes with α,α‐dichloroaldimines in 1,1,1,3,3,3‐hexafluoro‐2‐propanol as the sole solvent results in the rapid and selective formation of γ,γ‐dichloro‐β‐amino ketones. In this solvent the expected dichlorinated propargylamines and/or allylic amines are not formed. The dichloromethylene moiety of the aldimine acts as an activating group and is essential to accomplish this transformation. Electron‐rich acetylenes lead to the best results and work well with all imines (with or without α′‐H at the nitrogen substituent), while electron‐deficient acetylenes only reacted with N‐tert‐butylaldimines (no α′‐H). The mechanistic pathway showed 1,1,1,3,3,3‐hexafluoro‐2‐propanol to protonate the aldimine, which in the rate‐determining step will react with the arylacetylene to form a resonance‐stabilized allene cation, which is trapped by a HFIP molecule giving rise to an enol ether, which promptly hydrolyzes to furnish exclusively the β‐amino ketones. Using DFT techniques we found that the first C C bond forming step is the rate‐determining step and is associated with a barrier of about 21 kcal mol−1.
16.
Sylva íhalov Pawel Dziedzic Armando Crdova Jan Veselý 《Advanced Synthesis \u0026amp; Catalysis》2011,353(7):1096-1108
The highly enantioselective organo‐co‐catalytic aza‐Morita–Baylis–Hillman (MBH)‐type reaction between N‐carbamate‐protected imines and α,β‐unsaturated aldehydes has been developed. The organic co‐catalytic system of proline and 1,4‐diazabicyclo[2.2.2]octane (DABCO) enables the asymmetric synthesis of the corresponding N‐Boc‐ and N‐Cbz‐protected β‐amino‐α‐alkylidene‐aldehydes in good to high yields and up to 99% ee. In the case of aza‐MBH‐type addition of enals to phenylprop‐2‐ene‐1‐imines, the co‐catalytic reaction exhibits excellent 1,2‐selectivity. The organo‐co‐catalytic aza‐MBH‐type reaction can also be performed by the direct highly enantioselective addition of α,β‐unsaturated aldehydes to bench‐stable N‐carbamate‐protected α‐amidosulfones to give the corresponding β‐amino‐α‐alkylidene‐aldehydes with up to 99% ee. The organo‐co‐catalytic aza‐MBH‐type reaction is also an expeditious entry to nearly enantiomerically pure β‐amino‐α‐alkylidene‐amino acids and β‐amino‐α‐alkylidene‐lactams (99% ee). The mechanism and stereochemistry of the chiral amine and DABCO co‐catalyzed aza‐MBH‐type reaction are also discussed. 相似文献
17.
Michael Lloyd Richard Lloyd Philip Keene Andrew Osborne 《Journal of chemical technology and biotechnology (Oxford, Oxfordshire : 1986)》2007,82(12):1099-1106
BACKGROUND: Pharmaceutical companies continue to evaluate β‐amino acids and β‐lactams in a range of drug candidates. The development of a highly efficient and selective bioresolution of cyclic β‐lactam substrates could yield enantiopure lactams and β‐amino acids with medicinal potential. The aim of this work was to discover and develop a biocatalyst capable of selectively hydrolysing β‐lactam substrates. RESULTS: Screening of our in‐house culture collection led to the discovery of a microorganism, Rhodococcus globerulus (NCIMB 41042) with β‐lactamase activity. Whole‐cell bioresolutions of the β‐lactams 1–4 were successfully carried out and in all cases enantiomeric excesses of the residual lactam and amino acid product were found to be greater than 98%. For one example, the bioresolution was optimised to operate at 60 g L?1 substrate concentration with a 20% wt/wt cell paste loading. CONCLUSION: A microorganism, Rhodococcus globerulus (NCIMB 41042), capable of selectively hydrolysing a range of cyclic β‐lactams, has been discovered. A scalable whole‐cell bioresolution process has been developed, leading to the synthesis of multigram quantities of enantiomerically pure β‐lactams and β‐amino acids. Copyright © 2007 Society of Chemical Industry 相似文献
18.
Yunting Liu Youming Wang Haibin Song Zhenghong Zhou Chuchi Tang 《Advanced Synthesis \u0026amp; Catalysis》2013,355(13):2544-2549
An unprecedented organocatalytic enantioselective cascade Michael/hemiketalization/retro‐aldol reaction of 2‐[(E)‐2‐nitrovinyl]phenols and 2,4‐dioxo‐4‐arylbutanoates is described. With a bifunctional squaramide catalyst incorporating (1R,2R)‐1,2‐diphenylethane‐1,2‐diamine, the reactions afford products in 75–99% yields with 80–98% ee. This process provides an enantioselective pathway for the synthesis of chiral α‐keto esters, precursors of 3‐arylproline derivatives, δ‐amino α‐keto acids or cyclic α‐keto lactams.
19.
A straightforward and efficient method for the synthesis of nitrogen‐functionalized cyclopentane derivatives via [3+2] cycloaddition of enamines with donor‐acceptor cyclopropanes in the presence of catalytic amounts of various Lewis acids at room temperature has been developed; furthermore, the corresponding β‐amino acid was synthesized by monodecarboxylation and hydrogenolysis. An enantioenriched synthesis of nitrogen‐functionalized cyclopentane derivatives through dynamic kinetic asymmetric transformation of racemic donor‐acceptor cyclopropanes has also been achieved employing a copper complex [Cu(OTf)2‐ L1 ] as the catalyst affording an enantiomeric ratio up to 8:1.
20.
Tran Van Loc Tran Van Sung C. Kamperdick G. Adam 《Advanced Synthesis \u0026amp; Catalysis》2000,342(1):63-71
Triterpenes of betulinic acid type exhibit many interesting biological activities. Therefore a series of new 3α‐hydroxy‐lup‐20(29)‐ene‐23,28‐dioic acid derivatives 2a—22 with putative pharmacological activities were synthesized. As starting compounds 3α‐hydroxy‐lup‐20(29)‐ene‐23,28‐dioic acid ( 1a ), isolated from Schefflera octophylla, or its 3‐O‐acetyl derivative 1b were used. Mono‐ and diesters ( 2a—b from 1a , and 4d from 4c ) were prepared with CH2N2. Oxidation of the isopropenyl side chain with OsO4 yielded the 20,29‐diols ( 4a—b from 1b , and 19 from 17 ), which were in the case of 4b further transformed to the 29‐norketones 8a/mdash;b . Oxidation of the isopropenyl side chain with m‐chloroperbenzoic acid afforded the 20,29‐epoxide 12 (from 1b ) and the 29‐aldehydes and a‐hydroxy aldehydes ( 13a—c from 2a, 14a—c from 2b , and 16a—c from 15a ). Ring A was modified by a tosylation—elimination sequence using p‐TsCl/NaOAc, which afforded diolefin 15a (from 2a ) with Δ2,20(29) double bonds or 23‐nor‐Δ3,20(29)diolefin 17 (from 1a ). Compounds 4b, 4c , and 8a were coupled with L ‐methionin, L ‐phenylalanin, L ‐alanin, L ‐serin, and L ‐glutaminic acid via amide bonds at positions 23 and 28 to afford the amino acid conjugates 5a—7b and 9a—11 . 相似文献