共查询到20条相似文献,搜索用时 15 毫秒
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Hiroyuki Kakei Riichiro Tsuji Dr. Takashi Ohshima Dr. Hiroyuki Morimoto Shigeki Matsunaga Dr. Masakatsu Shibasaki Prof. Dr. 《化学:亚洲杂志》2007,2(2):257-264
The full details of the asymmetric epoxidation of α,β‐unsaturated esters catalyzed by yttrium complexes with biaryldiol ligands are described. An yttrium–biphenyldiol catalyst, generated from Y(OiPr)3–biphenyldiol ligand–triphenylarsine oxide (1:1:1), is suitable for the epoxidation of various α,β‐unsaturated esters. With this catalyst, β‐aryl α,β‐unsaturated esters gave high enantioselectivities and good yields (≤99 % ee). The reactivity of this catalyst is good, and the catalyst loading could be decreased to as little as 0.5–2 mol % (the turnover number was up to 116), while high enantiomeric excesses were maintained. For β‐alkyl α,β‐unsaturated esters, an yttrium–binol catalyst, generated from Y(OiPr)3–binol ligand–triphenylphosphine oxide (1:1:2), gave the best enantioselectivities (≤97 % ee). The utility of the epoxidation reaction was demonstrated in an efficient synthesis of (?)‐ragaglitazar, a potential antidiabetes agent. 相似文献
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Christine Gally Dr. Bettina M. Nestl Prof. Dr. Bernhard Hauer 《Angewandte Chemie (International ed. in English)》2015,54(44):12952-12956
The asymmetric dihydroxylation of olefins is of special interest due to the facile transformation of the chiral diol products into valuable derivatives. Rieske non‐heme iron oxygenases (ROs) represent promising biocatalysts for this reaction as they can be engineered to efficiently catalyze the selective mono‐ and dihydroxylation of various olefins. The introduction of a single point mutation improved selectivities (≥95 %) and conversions (>99 %) towards selected alkenes. By modifying the size of one active site amino acid side chain, we were able to modulate the regio‐ and stereoselectivity of these enzymes. For distinct substrates, mutants displayed altered regioselectivities or even favored opposite enantiomers compared to the wild‐type ROs, offering a sustainable approach for the oxyfunctionalization of a wide variety of structurally different olefins. 相似文献
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Phase‐Transfer‐Catalyzed Asymmetric SNAr Reaction of α‐Amino Acid Derivatives with Arene Chromium Complexes 下载免费PDF全文
Prof. Dr. Seiji Shirakawa Kenichiro Yamamoto Prof. Dr. Keiji Maruoka 《Angewandte Chemie (International ed. in English)》2015,54(3):838-840
Although phase‐transfer‐catalyzed asymmetric SNAr reactions provide unique contribution to the catalytic asymmetric α‐arylations of carbonyl compounds to produce biologically active α‐aryl carbonyl compounds, the electrophiles were limited to arenes bearing strong electron‐withdrawing groups, such as a nitro group. To overcome this limitation, we examined the asymmetric SNAr reactions of α‐amino acid derivatives with arene chromium complexes derived from fluoroarenes, including those containing electron‐donating substituents. The arylation was efficiently promoted by binaphthyl‐modified chiral phase‐transfer catalysts to give the corresponding α,α‐disubstituted α‐amino acids containing various aromatic substituents with high enantioselectivities. 相似文献
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Xiaohong Chen Yin Zhu Zhen Qiao Mingsheng Xie Lili Lin Dr. Xiaohua Liu Dr. Xiaoming Feng Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(33):10124-10129
An easily available and efficient chiral N,N′‐dioxide–nickel(II) complex catalyst has been developed for the direct catalytic asymmetric aldol reaction of α‐isothiocyanato imide with aldehydes which produces the products in morderate to high yields (up to 98 %) with excellent diastereo‐ (up to >99:1 d.r.) and enantioselectivities (up to >99 % ee). A variety of aromatic, heteroaromatic, α,β‐unsaturated, and aliphatic aldehydes were found to be suitable substrates in the presence of 2.5 mol % L ‐proline‐derived N,N′‐dioxide L5 –nickel(II) complex. This process was air‐tolerant and easily manipulated with available reagents. Based on experimental investigations, a possible transition state has been proposed to explain the origin of reactivity and asymmetric inductivity. 相似文献
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Yujiro Hayashi Prof. Dr. Kazuki Obi Yusuke Ohta Daichi Okamura Hayato Ishikawa Dr. 《化学:亚洲杂志》2009,4(2):246-249
Direct and enantioselective : Diphenylprolinol silyl ether was found to catalyze the direct, asymmetric Michael reaction of 4‐substituted 2‐aryl‐2‐oxazoline‐5‐one and α,β‐unsaturated aldehydes, affording the chiral α,α‐disubstituted α‐amino acid derivatives with excellent enantioselectivity.
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Lanning Li Bin Chen Yuanyuan Ke Qing Li Yue Zhuang Kun Duan Yichun Huang Dr. Jiyan Pang Prof. Dr. Liqin Qiu 《化学:亚洲杂志》2013,8(9):2167-2174
A valuable class of new heterocyclic and alicyclic prochiral α‐aminomethylacrylates has been conveniently synthesized through a three‐step transformation involving a Baylis–Hillman reaction, O‐acetylation, and a subsequent allylic amination. The corresponding novel β2‐amino acid derivatives were prepared with excellent enantioselectivities and high yields by catalytic asymmetric hydrogenation using the catalyst rhodium(Et‐Duphos) (Et‐Duphos=2′,5′,2′′,5′′‐tetraethyl‐1,2‐bis(phospholanyl)benzene)) under mild reaction conditions (up to 99 % ee and S/C=1000). The influence of the substrate on the enantioselectivity and reactivity is investigated, and the most suitable substrate configuration for the highly efficient enantioselective hydrogenation of β‐substituted α‐aminomethylacrylates under the Rh–Duphos system is reported. The current protocol provides a very practical, facile, and scalable method for the preparation of heterocyclic and alicyclic β2‐amino acids and their derivatives. 相似文献
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Zheng Wang Shuai Luo Dr. Shoude Zhang Wu‐Lin Yang Yang‐Zi Liu Prof. Dr. Honglin Li Prof. Dr. Xiaoyan Luo Prof. Dr. Wei‐Ping Deng 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(21):6739-6745
The first catalytic enantioselective 1,3‐dipolar cycloaddition of azomethine ylides to α‐aminoacrylate catalyzed by a AgOAc/ferrocenyl oxazolinylphosphine (FOXAP) system was developed, which exhibits excellent exo‐ and enantioselectivity (92–99 % ee). This process provides efficient access to useful 4‐aminopyrrolidine‐2,4‐dicarboxylic acid (APDC)‐like compounds containing a unique quaternary α‐amino acid unit. 相似文献
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Shaoquan Lin Dr. Naoya Kumagai Prof. Dr. Masakatsu Shibasaki 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(10):3296-3299
We report a direct catalytic asymmetric Mannich‐type addition of α,β‐unsaturated γ‐butyrolactam to α‐ethoxycarbonyl ketimines promoted by a soft Lewis acid/Brønsted base cooperative catalyst. A thiophosphinoyl group on the nitrogen of ketimines was crucial for both electrophilic activation and α‐addition of γ‐butyrolactams. The obtained aza‐Morita–Baylis–Hillman‐type products bear an α‐amino acid architecture with a tetra‐substituted stereogenic center. 相似文献
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Catalytic Enantioselective Synthesis of N,Cα,Cα‐Trisubstituted α‐Amino Acid Derivatives Using 1H‐Imidazol‐4(5H)‐ones as Key Templates 下载免费PDF全文
Julen Etxabe Joseba Izquierdo Dr. Aitor Landa Prof. Mikel Oiarbide Prof. Claudio Palomo 《Angewandte Chemie (International ed. in English)》2015,54(23):6883-6886
1H‐Imidazol‐4(5H)‐ones are introduced as novel nucleophilic α‐amino acid equivalents in asymmetric synthesis. These compounds not only allow highly efficient construction of tetrasubstituted stereogenic centers, but unlike hitherto known templates, provide direct access to N‐substituted (alkyl, allyl, aryl) α‐amino acid derivatives. 相似文献
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Catalytic Asymmetric 1,2‐Addition of α‐Isothiocyanato Phosphonates: Synthesis of Chiral β‐Hydroxy‐ or β‐Amino‐Substituted α‐Amino Phosphonic Acid Derivatives 下载免费PDF全文
Yi‐Ming Cao Fang‐Fang Shen Fu‐Ting Zhang Jin‐Long Zhang Prof. Dr. Rui Wang 《Angewandte Chemie (International ed. in English)》2014,53(7):1862-1866
α‐Amino phosphonic acid derivatives are considered to be the most important structural analogues of α‐amino acids and have a very wide range of applications. However, approaches for the catalytic asymmetric synthesis of such useful compounds are very limited. In this work, simple, efficient, and versatile organocatalytic asymmetric 1,2‐addition reactions of α‐isothiocyanato phosphonate were developed. Through these processes, derivatives of β‐hydroxy‐α‐amino phosphonic acid and α,β‐diamino phosphonic acid, as well as highly functionalized phosphonate‐substituted spirooxindole, can be efficiently constructed (up to 99 % yield, d.r. >20:1, and >99 % ee). This novel method provides a new route for the enantioselective functionalization of α‐phosphonic acid derivatives. 相似文献
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On the Mechanism of the Organocatalytic Asymmetric Epoxidation of α,β‐Unsaturated Aldehydes 下载免费PDF全文
Dr. Rebecca L. Davis Dr. Kim L. Jensen Dr. Björn Gschwend Prof. Dr. Karl Anker Jørgensen 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(1):64-67
Mechanistic studies on the organocatalytic epoxidation of α,β‐unsaturated aldehydes explore the autoinductive behavior of the reaction and establish that the hydrate/peroxyhydrate of the product is acting as a phase‐transfer catalyst. Based on these studies, an improved methodology that provides high selectivities and decreased catalyst loading, through the addition of chloral hydrate, is developed. 相似文献
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Rachel C. Atkinson Dr. Fernando Fernández‐Nieto Josep Mas Roselló Prof. Jonathan Clayden 《Angewandte Chemie (International ed. in English)》2015,54(31):8961-8965
Available α‐amino acids undergo arylation at their α position in an enantioselective manner on treatment with base of N′‐aryl urea derivatives ligated to pseudoephedrine as a chiral auxiliary. In situ silylation and enolization induces diastereoselective migration of the N′‐aryl group to the α position of the amino acid, followed by ring closure to a hydantoin with concomitant explulsion of the recyclable auxiliary. The hydrolysis of the hydantoin products provides derivatives of quaternary amino acids. The arylation avoids the use of heavy‐metal additives, and is successful with a range of amino acids and with aryl rings of varying electronic character. 相似文献