共查询到20条相似文献,搜索用时 62 毫秒
1.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(51):16511-16514
A highly stereoselective synthesis of hitherto less accessible chiral α‐tertiary amines with multiple structurally similar linear carbon chains was achieved through chiral auxiliary mediated addition of organolithium reagents to the geometrically well‐controlled alkynyl Z ‐ketimines. This stereoselective nucleophilic addition offers a general approach to the asymmetric synthesis of nitrogen‐containing chiral materials. 相似文献
2.
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
3.
Stereoselective Synthesis of α‐3‐Deoxy‐D‐manno‐oct‐2‐ulosonic Acid (α‐Kdo) Glycosides Using 5,7‐O‐Di‐tert‐butylsilylene‐Protected Kdo Ethyl Thioglycoside Donors 下载免费PDF全文
Jia‐Sheng Huang Wei Huang Xue Meng Xin Wang Peng‐Cheng Gao Prof. Dr. Jin‐Song Yang 《Angewandte Chemie (International ed. in English)》2015,54(37):10894-10898
An efficient methodology for the synthesis of α‐Kdo glycosidic bonds has been developed with 5,7‐O‐di‐tert‐butylsilylene (DTBS) protected Kdo ethyl thioglycosides as glycosyl donors. The approach permits a wide scope of acceptors to be used, thus affording biologically significant Kdo glycosides in good to excellent chemical yields with complete α‐selectivity. The synthetic utility of an orthogonally protected Kdo donor has been demonstrated by concise preparation of two α‐Kdo‐containing oligosaccharides. 相似文献
4.
2,4‐Dinitrophenol‐Catalyzed α‐C(sp3)−H and C(sp)−H Bond Functionalization of Cyclic Amines and Alkynes: Highly Regio‐/Diastereoselective Synthesis of α‐Alkynyl‐3‐Amino‐2‐Oxindoles 下载免费PDF全文
Dr. Mukesh Kumar Banni P. Kaur Prof. Swapandeep S Chimni 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(29):9948-9952
A transition‐metal‐ and oxidant‐free DNP (2,4‐dinitrophenol)‐catalyzed atom‐economical regio‐ and diastereoselective synthesis of monofunctionalized α‐alkynyl‐3‐amino‐2‐oxindole derivatives by C?H bond functionalization of cyclic amines and alkynes with indoline‐2,3‐diones has been developed. This cascade event sequentially involves the reductive amination of indoline‐2,3‐dione by imine formation and cross coupling between C(sp3)?H and C(sp)?H of the cyclic amines and alkynes. This reaction offers an efficient and attractive pathway to different types of α‐alkynyl‐3‐amino‐2‐oxindole derivatives in good yields with a wide tolerance of functional groups. The salient feature of this methodology is that it completely suppresses the homocoupling of alkynes. To the best of our knowledge, this is the first example of a DNP‐catalyzed metal‐free direct C(sp3)?H and C(sp)?H bond functionalization providing biologically active α‐alkynyl‐3‐amino‐2‐oxindole scaffolds. 相似文献
5.
Engineered L‐Serine Hydroxymethyltransferase from Streptococcus thermophilus for the Synthesis of α,α‐Dialkyl‐α‐Amino Acids 下载免费PDF全文
Karel Hernandez Igor Zelen Giovanna Petrillo Prof. Dr. Isabel Usón Claudia M. Wandtke Dr. Jordi Bujons Dr. Jesús Joglar Dr. Teodor Parella Prof. Dr. Pere Clapés 《Angewandte Chemie (International ed. in English)》2015,54(10):3013-3017
α,α‐Disubstituted α‐amino acids are central to biotechnological and biomedical chemical processes for their own sake and as substructures of biologically active molecules for diverse biomedical applications. Structurally, these compounds contain a quaternary stereocenter, which is particularly challenging for stereoselective synthesis. The pyridoxal‐5′‐phosphate (PLP)‐dependent L ‐serine hydroxymethyltransferase from Streptococcus thermophilus (SHMTSth; EC 2.1.2.1) was engineered to achieve the stereoselective synthesis of a broad structural variety of α,α‐dialkyl‐α‐amino acids. This was accomplished by the formation of quaternary stereocenters through aldol addition of the amino acids D ‐Ala and D ‐Ser to a wide acceptor scope catalyzed by the minimalist SHMTSth Y55T variant overcoming the limitation of the native enzyme for Gly. The SHMTSth Y55T variant tolerates aromatic and aliphatic aldehydes as well as hydroxy‐ and nitrogen‐containing aldehydes as acceptors. 相似文献
6.
Umpolung Reactions of α‐Imino Esters: Useful Methods for the Preparation of α‐Amino Acid Frameworks 下载免费PDF全文
This paper summarizes our recent efforts toward the development of tandem reactions utilizing umpolung reactions of α‐imino esters. A highly diastereoselective tandem N‐alkylation–Mannich reaction of α‐imino esters was developed. A tandem N‐alkylation–addition reaction of α‐imino esters derived from ethyl glyoxylate with various aldehydes proceeded to give 1,2‐amino alcohols. The same reaction also proceeded efficiently using a novel flow system comprising two connected microreactors. Novel syntheses of α‐quaternary alkynyl amino esters and allenoates were developed through the use of umpolung N‐addition to β,γ‐alkynyl α‐imino esters, followed by regioselective acylation. In addition, a highly regioselective tandem N‐alkylation–vinylogous aldol reaction of β,γ‐alkenyl α‐imino esters was discovered. N‐Alkylation of α‐iminophosphonates followed by a Horner–Wadsworth–Emmons reaction with aldehydes occurred to afford enamines, which can be used in a four‐component coupling reaction with methyl vinyl ketone. α‐N‐Acyloxyimino esters served as highly efficient substrates for the N,N,C‐trialkylation reaction to introduce various nucleophiles at the imino nitrogen and carbon atoms. 相似文献
7.
Rhodium‐catalyzed Asymmetric Hydrogenation of α‐Dehydroamino Ketones: A General Approach to Chiral α‐amino Ketones 下载免费PDF全文
Rhodium/DuanPhos‐catalyzed asymmetric hydrogenation of aliphatic α‐dehydroamino ketones has been achieved and afforded chiral α‐amino ketones in high yields and excellent enantioselectives (up to 99 % ee), which could be reduced further to chiral β‐amino alcohols by LiAlH(tBuO)3 with good yields. This protocol provides a readily accessible route for the synthesis of chiral α‐amino ketones and chiral β‐amino alcohols. 相似文献
8.
Selective Hydrogen Atom Abstraction through Induced Bond Polarization: Direct α‐Arylation of Alcohols through Photoredox,HAT, and Nickel Catalysis 下载免费PDF全文
Jack Twilton Melodie Christensen Dr. Daniel A. DiRocco Dr. Rebecca T. Ruck Dr. Ian W. Davies Prof. Dr. David W. C. MacMillan 《Angewandte Chemie (International ed. in English)》2018,57(19):5369-5373
The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α‐hydroxy C?H bonds. This approach employs zinc‐mediated alcohol deprotonation to activate α‐hydroxy C?H bonds while simultaneously suppressing C?O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn‐based Lewis acids also deactivates other hydridic bonds such as α‐amino and α‐oxy C?H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3‐step synthesis of the drug Prozac exemplifies the utility of this new method. 相似文献
9.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2018,130(19):5467-5471
The combination of nickel metallaphotoredox catalysis, hydrogen atom transfer catalysis, and a Lewis acid activation mode, has led to the development of an arylation method for the selective functionalization of alcohol α‐hydroxy C−H bonds. This approach employs zinc‐mediated alcohol deprotonation to activate α‐hydroxy C−H bonds while simultaneously suppressing C−O bond formation by inhibiting the formation of nickel alkoxide species. The use of Zn‐based Lewis acids also deactivates other hydridic bonds such as α‐amino and α‐oxy C−H bonds. This approach facilitates rapid access to benzylic alcohols, an important motif in drug discovery. A 3‐step synthesis of the drug Prozac exemplifies the utility of this new method. 相似文献
10.
Dr. Tsuyoshi Mita Yuki Higuchi Prof. Dr. Yoshihiro Sato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2013,19(3):1123-1128
α‐Amino acids are essential resources for human life and are highly useful as building blocks for organic synthesis. The core framework of an α‐amino acid can be divided into three basic components: an aldehyde, an amine, and carbon dioxide (CO2). We report herein that a one‐step synthesis of α‐amino acids has been successfully achieved from these three basic and inexpensive chemicals with a single operation, in which the mixture of an aldehyde, a sulfonamide, and gaseous CO2 was heated at 100 °C in the presence of Bu3Sn‐SnBu3 and CsF. In this one‐pot sequential protocol, two important intermediates (imine and α‐amino stannane) are involved and the stannyl anion generated in situ plays a crucial role, particularly for the efficient stannylation of the imine in the presence of proton sources and for promoting retrostannylation of the undesired α‐alkoxy stannane owing to its high stability and tolerance of the presence of proton sources. This methodology enabled the synthesis of a wide range of racemic arylglycine derivatives in high yields. 相似文献
11.
Hai‐Tao Tang Yun‐Bing Zhou Yu Zhu Hong‐Chao Sun Min Lin Prof. Zhuang‐Ping Zhan 《化学:亚洲杂志》2014,9(5):1278-1281
An efficient Cs2CO3‐promoted synthesis of α‐amino ketones using hydrazines, aldehydes, and α‐haloketones as starting materials through a cascade condensation/nucleophilic substitution/N? N bond cleavage route is developed. The carbonyl group plays a key role in this novel N? N bond cleavage process. 相似文献
12.
Regioselective Insertion of o‐Carborynes into the α‐CH Bond of Tertiary Amines: Synthesis of α‐Carboranylated Amines 下载免费PDF全文
Da Zhao Jiji Zhang Prof. Dr. Zuowei Xie 《Angewandte Chemie (International ed. in English)》2014,53(47):12902-12906
o‐Carboryne can undergo α‐C? H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C? H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes. 相似文献
13.
Da Zhao Jiji Zhang Zuowei Xie 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2014,126(47):13116-13120
o‐Carboryne can undergo α‐C H bond insertion with tertiary amines, thus affording α‐carboranylated amines in very good regioselectivity and isolated yields. In this process, the nucleophilic addition of tertiary amines to the multiple bond of o‐carboryne generates a zwitterionic intermediate. An intramolecular proton transfer, followed by a nucleophilic attack leads to the formation of the final product. Thus, regioselectivity is highly dependent upon the acidity of α‐C H proton of tertiary amines. This approach serves as an efficient methodology for the preparation of a series of 1‐aminoalkyl‐o‐carboranes. 相似文献
14.
Yasumasa Hamada 《Chemical record (New York, N.Y.)》2014,14(2):235-250
This review describes our recent works on the diastereo‐ and enantioselective synthesis of anti‐β‐hydroxy‐α‐amino acid esters using transition‐metal–chiral‐bisphosphine catalysts. A variety of transition metals, namely ruthenium (Ru), rhodium (Rh),iridium (Ir), and nickel (Ni), in combination with chiral bisphosphines, worked well as catalysts for the direct anti‐selective asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides, yielding anti‐β‐hydroxy‐α‐amino acid esters via dynamic kinetic resolution (DKR) in excellent yields and diastereo‐ and enantioselectivities. The Ru‐catalyzed asymmetric hydrogenation of α‐amino‐β‐ketoesters via DKR is the first example of generating anti‐β‐hydroxy‐α‐amino acids. Complexes of iridium and axially chiral bisphosphines catalyze an efficient asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides via dynamic kinetic resolution. A homogeneous Ni–chiral‐bisphosphine complex also catalyzes an efficient asymmetric hydrogenation of α‐amino‐β‐keto ester hydrochlorides in an anti‐selective manner. As a related process, the asymmetric hydrogenation of the configurationally stable substituted α‐aminoketones using a Ni catalyst via DKR is also described. 相似文献
15.
Recent Advances in the Synthesis of Heterocycles and Related Substances Based on α‐Imino Rhodium Carbene Complexes Derived from N‐Sulfonyl‐1,2,3‐triazoles 下载免费PDF全文
Yu Jiang Run Sun Prof. Dr. Xiang‐Ying Tang Prof. Dr. Min Shi 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(50):17910-17924
In recent years, α‐imino rhodium carbene complexes derived by ring‐opening of N‐sulfonyl‐1,2,3‐triazoles have attracted much attention from organic chemists. Many transformations of these species have been reported that involve, in most cases, nucleophilic attack at the carbene center of the α‐imino rhodium carbene, facilitating the synthesis of a wide range of novel and useful compounds, particularly heterocycles. This Minireview mainly focuses on advances in the transformation of N‐sulfonyl‐1,2,3‐triazoles during the past two years. 相似文献
16.
Ting Zhao Katarzyna Kurpiewska Justyna Kalinowska‐Tłuścik Eberhardt Herdtweck Prof. Dr. Alexander Dömling 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(9):3009-3018
The synthesis of all 20 common natural proteinogenic and 4 otherα‐amino acid‐isosteric α‐amino tetrazoles has been accomplished, whereby the carboxyl group is replaced by the isosteric 5‐tetrazolyl group. The short process involves the use of the key Ugi tetrazole reaction followed by deprotection chemistries. The tetrazole group is bioisosteric to the carboxylic acid and is widely used in medicinal chemistry and drug design. Surprisingly, several of the common α‐amino acid‐isosteric α‐amino tetrazoles are unknown up to now. Therefore a rapid synthetic access to this compound class and non‐natural derivatives is of high interest to advance the field. 相似文献
17.
Koichi Koga Atsushi Sudo Haruo Nishida Takeshi Endo 《Journal of polymer science. Part A, Polymer chemistry》2009,47(15):3839-3844
A new convenient synthesis of N‐carboxyanhydrides (NCAs) of α‐amino acids was achieved by selective cyclization of urethane derivatives of α‐amino acids. The urethanes were readily synthesized via N‐carbamoylation of α‐amino acids by bis(4‐nitrophenyl)carbonate quantitatively. These urethanes having 4‐nitrophenoxy moiety were tolerant to air and moisture to allow their facile purification and storage. When the obtained urethanes were heated in 2‐butanone at 60 °C, they underwent the selective cyclization via intramolecular nucleophilic attack of the carboxyl moiety to the urethane moiety with releasing 4‐nitrophenol, leading to the successful formation of the corresponding NCAs. Addition of carboxylic acids remarkably stabilized the formed NCAs during the reaction, allowing their isolation in high yields. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 3839–3844, 2009 相似文献
18.
Dipl.‐Chem. Manuel Weber Dr. Sascha Jautze Dr. Wolfgang Frey Prof. Dr. René Peters 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(46):14792-14804
The development and further evolution of the first catalytic asymmetric conjugate additions of azlactones as activated amino acid derivatives to enones is described. Whereas the first‐generation approach started from isolated azlactones, in the second‐generation approach the azlactones could be generated in situ starting from racemic N‐benzoylated amino acids. The third evolution stage could make use of racemic unprotected α‐amino acids to directly form highly enantioenriched and diastereomerically pure masked quaternary amino acid products bearing an additional tertiary stereocenter. The step‐economic transformations were accomplished by cooperative activation by using a robust planar chiral bis‐Pd catalyst, a Brønsted acid (HOAc or BzOH; Ac=acetyl, Bz=benzoyl), and a Brønsted base (NaOAc). In particular the second‐ and third‐generation approaches provide a rapid and divergent access to biologically interesting unnatural quaternary amino acid derivatives from inexpensive bulk chemicals. In that way highly enantioenriched acyclic α‐amino acids, α‐alkyl proline, and α‐alkyl pyroglutamic acid derivatives could be prepared in diastereomerically pure form. In addition, a unique way is presented to prepare diastereomerically pure bicyclic dipeptides in just two steps from unprotected tertiary α‐amino acids. 相似文献
19.
C‐Selective and Diastereoselective Alkyl Addition to β,γ‐Alkynyl‐α‐imino Esters with Zinc(II)ate Complexes 下载免费PDF全文
Dr. Manabu Hatano Kenji Yamashita Mai Mizuno Orie Ito Prof. Dr. Kazuaki Ishihara 《Angewandte Chemie (International ed. in English)》2015,54(9):2707-2711
Since umpolung α‐imino esters contain three electrophilic centers, regioselective alkyl addition with traditional organometallic reagents has been a serious problem in the practical synthesis of versatile chiral α‐amino acid derivatives. An unusual C‐alkyl addition to α‐imino esters using a Grignard reagent (RMgX)‐derived zinc(II)ate was developed. Zinc(II)ate complexes consist of a Lewis acidic [MgX]+ moiety, a nucleophilic [R3Zn]? moiety, and 2 [MgX2]. Therefore, the ionically separated [R3Zn]? selectively attacks the imino carbon atom ,which is most strongly activated by chelation of [MgX]+. In particular, chiral β,γ‐alkynyl‐α‐imino esters can strongly promote highly regio‐ and diastereoselective C‐alkylation because of structural considerations, and the corresponding optically active α‐quaternary amino acid derivatives are obtained within 5 minutes in high to excellent yields. 相似文献
20.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(51):16560-16564
A novel approach for the umpolung α‐arylation of amides is presented. By the nucleophilic phenylation of O‐silyl N,O‐ketene acetals, generated in situ from N‐alkoxy amides, a phenyl group can be introduced onto the α‐carbon atom of amides through N−O bond cleavage in a two‐step, one‐pot process. The asymmetric synthesis of α‐aryl amides through the diastereoselective arylation of a chiral N,O‐ketene acetal is also described. 相似文献