共查询到20条相似文献,搜索用时 15 毫秒
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Zhipeng Yu Xiaohua Liu Dr. Lin Zhou Lili Lin Dr. Xiaoming Feng Prof. Dr. 《Angewandte Chemie (International ed. in English)》2009,48(28):5195-5198
Two activations are better than one : The chiral bifunctional guanidine 1 , which features an amino amide backbone, catalyzes the asymmetric Michael addition of a range of substrates and gives products with excellent stereoselectivities. The method also allows the efficient synthesis of optically pure β‐amino acid esters. Both the guanidine group and the NH proton of the amide were important for the dual activation.
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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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Andrea‐Nekane R. Alba Xavier Companyó Guillem Valero Albert Moyano Prof. Dr. Ramon Rios Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(18):5354-5361
A new, easy, and highly enantioselective method for the synthesis of quaternary α‐alkyl‐α‐amino acids based on organocatalysis is reported. The addition of oxazolones to 1,1‐bis(phenylsulfonyl)ethylene is efficiently catalyzed by simple chiral bases or thioureas. The reaction affords α,α‐disubstituted α‐amino acid derivatives with complete C4 regioselectivity and with excellent yields and enantioselectivities. This methodology is complementary to previously reported enantioselective approaches to quaternary α‐amino acids and allows the synthesis of α‐phenyl‐α‐alkyl‐α‐amino acids and α‐tert‐butyl‐α‐alkyl‐α‐amino acids. It has distinct advantages in terms of operational simplicity, enviromentally friendly conditions, and suitability for large‐scale reactions. 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 Construction of α‐Quaternary Cyclopentanones and Its Application to the Syntheses of (−)‐1,14‐Herbertenediol and (−)‐Aphanorphine 下载免费PDF全文
Dao‐Yong Zhu Ming‐Hui Xu Prof. Dr. Yong‐Qiang Tu Prof. Dr. Fu‐Min Zhang Prof. Dr. Shao‐Hua Wang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(44):15502-15505
A novel and efficient strategy to build α‐benzylic quaternary cyclopentanones with excellent enantioselectivities (up to 96 % ee) and high yields (up to 99 % yield) has been developed, and its application demonstrated by the first catalytic asymmetric total synthesis of (?)‐1,14‐herbertenediol and the formal synthesis of (?)‐aphanorphine. 相似文献
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Quaternary β2,2‐Amino Acids: Catalytic Asymmetric Synthesis and Incorporation into Peptides by Fmoc‐Based Solid‐Phase Peptide Synthesis 下载免费PDF全文
Dr. Jin‐Sheng Yu Dr. Hidetoshi Noda Prof. Dr. Masakatsu Shibasaki 《Angewandte Chemie (International ed. in English)》2018,57(3):818-822
β‐Amino acid incorporation has emerged as a promising approach to enhance the stability of parent peptides and to improve their biological activity. Owing to the lack of reliable access to β2,2‐amino acids in a setting suitable for peptide synthesis, most contemporary research efforts focus on the use of β3‐ and certain β2,3‐amino acids. Herein, we report the catalytic asymmetric synthesis of β2,2‐amino acids and their incorporation into peptides by Fmoc‐based solid‐phase peptide synthesis (Fmoc‐SPPS). A quaternary carbon center was constructed by the palladium‐catalyzed decarboxylative allylation of 4‐substituted isoxazolidin‐5‐ones. The N?O bond in the products not only acts as a traceless protecting group for β‐amino acids but also undergoes amide formation with α‐ketoacids derived from Fmoc‐protected α‐amino acids, thus providing expeditious access to α‐β2,2‐dipeptides ready for Fmoc‐SPPS. 相似文献
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Stereocontrolled Synthesis of syn‐β‐Hydroxy‐α‐Amino Acids by Direct Aldolization of Pseudoephenamine Glycinamide 下载免费PDF全文
Dr. Ian B. Seiple Jaron A. M. Mercer Robin J. Sussman Ziyang Zhang Prof. Dr. Andrew G. Myers 《Angewandte Chemie (International ed. in English)》2014,53(18):4642-4647
β‐Hydroxy‐α‐amino acids figure prominently as chiral building blocks in chemical synthesis and serve as precursors to numerous important medicines. Reported herein is a method for the synthesis of β‐hydroxy‐α‐amino acid derivatives by aldolization of pseudoephenamine glycinamide, which can be prepared from pseudoephenamine in a one‐flask protocol. Enolization of (R,R)‐ or (S,S)‐pseudoephenamine glycinamide with lithium hexamethyldisilazide in the presence of LiCl followed by addition of an aldehyde or ketone substrate affords aldol addition products that are stereochemically homologous with L ‐ or D ‐threonine, respectively. These products, which are typically solids, can be obtained in stereoisomerically pure form in yields of 55–98 %, and are readily transformed into β‐hydroxy‐α‐amino acids by mild hydrolysis or into 2‐amino‐1,3‐diols by reduction with sodium borohydride. This new chemistry greatly facilitates the construction of novel antibiotics of several different classes. 相似文献
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Jie Yang Xiao‐Ming Zhang Fu‐Min Zhang Shao‐Hua Wang Yong‐Qiang Tu Zhen Li Xi‐Chao Wang Hong Wang 《Angewandte Chemie (International ed. in English)》2020,59(22):8471-8475
An enantioselective aldehyde α‐alkylation/semipinacol rearrangement was achieved through organo‐SOMO catalysis. The catalytically generated enamine radical cation serves as a carbon radical electrophile that can stereoselectively add to the alkene of an allylic alcohol and initiate ensuing ring‐expansion of cyclopropanol or cyclobutanol. This tandem reaction enables the production of a wide range of nonracemic functionalizable α‐quaternary‐δ‐carbonyl cycloketones in high yields and excellent enantioselectivity from simple aldehydes and allylic alcohols. As a key step, the intramolecular reaction was also successfully applied in the asymmetric total synthesis of (+)‐cerapicol. 相似文献
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Vincent Terrasson Dr. Renata Marcia de Figueiredo Dr. Jean Marc Campagne Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(26):7875-7880
An enantioselective cyclopropanation of α‐substituted α,β‐unsaturated aldehydes with bromomalonate has been successfully developed through a domino Michael/α‐alkylation strategy. The method allows the efficient formation of cyclopropanes bearing a quaternary carbon stereocenter at the α‐position of the aldehydes by using iminium/enamine catalysis and gives a nice extension on the organocatalytic cyclopropanation of bromomalonate and α,β‐unsaturated aldehydes previously reported by other groups. Very good yields (up to 81 %) and enantioselectivities (up to 97 % ee) have been obtained. The optically active cyclopropane derivatives are of high synthetic interest as useful targets for further elaboration into more complex structures. 相似文献
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Motohiro Yasui Ayano Yamada Chihiro Tsukano Andrea Hamza Imre Ppai Yoshiji Takemoto 《Angewandte Chemie (International ed. in English)》2020,59(32):13479-13483
Although acetalization is a fundamental transformation in organic synthesis, intermolecular asymmetric acetalization remains an unsolved problem. In this study, a thiourea‐ammonium hybrid catalyst was shown to promote the O‐alkylation of enols with a racemic γ‐chlorobutenolide through dynamic kinetic resolution to give chiral acetals with good enantioselectivity. The catalyst simultaneously activates both the nucleophile and electrophile in a multifunctional manner. This method was applied to the asymmetric synthesis of several strigolactones. DFT calculations suggest that hydrogen‐bonding interactions between the chlorine atom of the γ‐chlorobutenolide and the tosylamide hydrogen atom of the catalyst, as well as other types of noncovalent catalyst–substrate interactions, are crucial for achieving high stereoselectivity. 相似文献
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An improved procedure for the asymmetric synthesis of α-aminoalkylphosphonic acids using S-2-anilinomethylpyrrolidine as the chiral auxiliary was described. The chemical transformations involved in this protocol could proceed under mild reaction condition to provide good chemical and enantiomeric yields. 相似文献