共查询到20条相似文献,搜索用时 29 毫秒
1.
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
2.
The organocatalytic properties of unnatural α‐amino acids are reviewed. Post‐translational derivatives of natural α‐amino acids include 4‐hydroxy‐l ‐proline and 4‐amino‐l ‐proline scaffolds, and also proline homologues. The activity of synthetic unnatural α‐amino acid‐based organocatalysts, such as β‐alkyl alanines, alanine‐based phosphines, and tert‐leucine derivatives, are reviewed herein. The organocatalytic properties of unnatural monocyclic, bicyclic, and tricyclic proline derivatives are also reviewed. Several families of these organocatalysts permit the efficient and stereoselective synthesis of complex natural products. Most of the reviewed organocatalysts accelerate the reported reactions through covalent interactions that raise the HOMO (enamine intermediates) or lower the LUMO (iminium intermediates). 相似文献
3.
Hossay Abas Josep Mas‐Rosell Mostafa Mahmoud Amer Derek J. Durand Robin R. Groleau Natalie Fey Jonathan Clayden 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(8):2440-2444
Both E‐ and Z‐N′‐alkenyl urea derivatives of imidazolidinones may be formed selectively from enantiopure α‐amino acids. Generation of their enolate derivatives in the presence of K+ and [18]crown‐6 induces intramolecular migration of the alkenyl group from N′ to Cα with retention of double bond geometry. DFT calculations indicate a partially concerted substitution mechanism. Hydrolysis of the enantiopure products under acid conditions reveals quaternary α‐alkenyl amino acids with stereodivergent control of both absolute configuration and double bond geometry. 相似文献
4.
Direct Catalytic Asymmetric Mannich‐type Reaction of α,β‐Unsaturated γ‐Butyrolactam with Ketimines 下载免费PDF全文
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
5.
Synthesis and Conformational Analysis of Hybrid α/β‐Dipeptides Incorporating S‐Glycosyl‐β2,2‐Amino Acids 下载免费PDF全文
Iván García‐González Dr. Lara Mata Dr. Francisco Corzana Dr. Gonzalo Jiménez‐Osés Prof. Alberto Avenoza Dr. Jesús H. Busto Prof. Jesús M. Peregrina 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(3):1156-1168
We synthesized and carried out the conformational analysis of several hybrid dipeptides consisting of an α‐amino acid attached to a quaternary glyco‐β‐amino acid. In particular, we combined a S‐glycosylated β2,2‐amino acid and two different types of α‐amino acid, namely, aliphatic (alanine) and aromatic (phenylalanine and tryptophan) in the sequence of hybrid α/β‐dipeptides. The key step in the synthesis involved the ring‐opening reaction of a chiral cyclic sulfamidate, inserted in the peptidic sequence, with a sulfur‐containing nucleophile by using 1‐thio‐β‐D ‐glucopyranose derivatives. This reaction of glycosylation occurred with inversion of configuration at the quaternary center. The conformational behavior in aqueous solution of the peptide backbone and the glycosidic linkage for all synthesized hybrid glycopeptides was analyzed by using a protocol that combined NMR experiments and molecular dynamics with time‐averaged restraints (MD‐tar). Interestingly, the presence of the sulfur heteroatom at the quaternary center of the β‐amino acid induced θ torsional angles close to 180° (anti). Notably, this value changed to 60° (gauche) when the peptidic sequence displayed aromatic α‐amino acids due to the presence of CH–π interactions between the phenyl or indole ring and the methyl groups of the β‐amino acid unit. 相似文献
6.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(6):1528-1531
Herein we report acid‐directed β‐C(sp3)‐H arylation of α‐amino acids enabled by pyridine‐type ligands. This reaction does not require the installation of an exogenous directing group, is scalable, and enables the preparation of Fmoc‐protected unnatural amino acids in three steps. The pyridine‐type ligands are crucial for the development of this new C(sp3)‐H arylation. 相似文献
7.
Rui Fu Soon Mog So Alan J. Lough Jik Chin 《Angewandte Chemie (International ed. in English)》2020,59(11):4335-4339
l to d conversion of unactivated α‐amino acids was achieved by solubility‐induced diastereomer transformation (SIDT). Ternary complexes of an α‐amino acid with 3,5‐dichlorosalicylaldehyde and a chiral guanidine (derived from corresponding chiral vicinal diamine) were obtained in good yield as diastereomerically pure imino acid salt complexes and were hydrolysed to obtain enantiopure α‐amino acids. A combination of DFT computation, NMR spectroscopy, and crystal structure provide detailed insight into how two types of strong hydrogen bonds assist in rapid epimerization of the complexes that is essential for SIDT. 相似文献
8.
Cangsong Liao Florian P. Seebeck 《Angewandte Chemie (International ed. in English)》2020,59(18):7184-7187
This report describes a modular enzyme‐catalyzed cascade reaction that transforms l ‐ or d ‐α‐amino acids to β‐methyl‐α‐amino acids. In this process an α‐amino acid transaminase, an α‐keto acid methyltransferase, and a halide methyltransferase cooperate in two orthogonal reaction cycles that mediate product formation and regeneration of the cofactor pyridoxal‐5′‐phosphate and the co‐substrate S‐adenosylmethionine. The only stoichiometric reagents consumed in this process are the unprotected l ‐ or d ‐α‐amino acid and methyl iodide. 相似文献
9.
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
10.
Decarbonylative Radical Coupling of α‐Aminoacyl Tellurides: Single‐Step Preparation of γ‐Amino and α,β‐Diamino Acids and Rapid Synthesis of Gabapentin and Manzacidin A 下载免费PDF全文
Dr. Masanori Nagatomo Hayato Nishiyama Haruka Fujino Prof. Dr. Masayuki Inoue 《Angewandte Chemie (International ed. in English)》2015,54(5):1537-1541
A new radical‐based coupling method has been developed for the single‐step generation of various γ‐amino acids and α,β‐diamino acids from α‐aminoacyl tellurides. Upon activation by Et3B and O2 at ambient temperature, α‐aminoacyl tellurides were readily converted into α‐amino carbon radicals through facile decarbonylation, which then reacted intermolecularly with acrylates or glyoxylic oxime ethers. This mild and powerful method was effectively incorporated into expeditious synthetic routes to the pharmaceutical agent gabapentin and the natural product (?)‐manzacidin A. 相似文献
11.
《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2017,129(36):10890-10894
α‐Amino nitriles tethered to alkenes through a urea linkage undergo intramolecular C‐alkenylation on treatment with base by attack of the lithionitrile derivatives on the N′‐alkenyl group. A geometry‐retentive alkene shift affords stereospecifically the E or Z isomer of the 5‐alkenyl‐4‐iminohydantoin products from the corresponding starting E ‐ or Z ‐N ′‐alkenyl urea, each of which may be formed from the same N ‐allyl precursor by stereodivergent alkene isomerization. The reaction, formally a nucleophilic substitution at an sp2 carbon atom, allows the direct regioselective incorporation of mono‐, di‐, tri‐, and tetrasubstituted olefins at the α‐carbon of amino acid derivatives. The initially formed 5‐alkenyl iminohydantoins may be hydrolyzed and oxidatively deprotected to yield hydantoins and unsaturated α‐quaternary amino acids. 相似文献
12.
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
13.
N. Chary Mamillapalli Prof. Govindasamy Sekar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(51):18584-18588
Synthesis of enantiomerically enriched α‐hydroxy amides and β‐amino alcohols has been accomplished by enantioselective reduction of α‐keto amides with hydrosilanes. A series of α‐keto amides were reduced in the presence of chiral CuII/(S)‐DTBM‐SEGPHOS catalyst to give the corresponding optically active α‐hydroxy amides with excellent enantioselectivities by using (EtO)3SiH as a reducing agent. Furthermore, a one‐pot complete reduction of both ketone and amide groups of α‐keto amides has been achieved using the same chiral copper catalyst followed by tetra‐n‐butylammonium fluoride (TBAF) catalyst in presence of (EtO)3SiH to afford the corresponding chiral β‐amino alcohol derivatives. 相似文献
14.
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
15.
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
16.
The mixing enthalpies of aqueous heavy rare alkali metal chloride RbC1 solutions with aqueous α-amino acid (Loglycine, L-alanine and α-aminobutyric acid) solutions, as well as the dilution enthalpies of RbC1 and α-amino acid solutions in pure water had been measured at 298.15K. The transfer enthalpies of RbCI from pure water to aqueous α-amino acid solutions could be obtained from these data. The enthalpic pair interaction parameters of RbC1 with α-amino acid in water have been evaluated according to the McMillan-Mayer theory and discussed in terms of the electrostatic interaction, structure interaction and Savage-wood group additivity mode. 相似文献
17.
Junxian Yang Zheng Wang Zeyuan He Guofeng Li Liang Hong Wangsheng Sun Rui Wang 《Angewandte Chemie (International ed. in English)》2020,59(2):642-647
The first asymmetric synthesis of tetrasubstituted α‐amino allenoates by a chiral phosphoric acid catalyzed dearomative γ‐addition reaction of 2,3‐disubstituted indoles to β,γ‐alkynyl‐α‐imino esters is reported. This method provides access to a series of highly functionalized tetrasubstituted allenes featuring quaternary stereocenters in high yields, and with excellent regio‐, diastereo‐, and enantioselectivities under mild conditions without by‐product formation. Representative large‐scale reactions and diverse transformations of the products into various scaffolds with potential biological activities render are also disclosed. The mechanism of the reaction was elucidated by control reactions and DFT calculations. 相似文献
18.
Li‐Wei Zhao Hui‐Min Shi Jiu‐Zhao Wang Prof. Jing He 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(48):15323-15329
An efficient ligand design strategy towards boosting asymmetric induction was proposed, which simply employed inorganic nanosheets to modify α‐amino acids and has been demonstrated to be effective in vanadium‐catalyzed epoxidation of allylic alcohols. Here, the strategy was first extended to zinc‐catalyzed asymmetric aldol reaction, a versatile bottom‐up route to make complex functional compounds. Zinc, the second‐most abundant transition metal in humans, is an environment‐friendly catalytic center. The strategy was then further proved valid for organocatalyzed metal‐free asymmetric catalysis, that is, α‐amino acid catalyzed asymmetric aldol reaction. Visible improvement of enantioselectivity was experimentally achieved irrespective of whether the nanosheet‐attached α‐amino acids were applied as chiral ligands together with catalytic ZnII centers or as chiral catalysts alone. The layered double hydroxide nanosheet was clearly found by theoretical calculations to boost ee through both steric and H‐bonding effects; this resembles the role of a huge and rigid substituent. 相似文献
19.
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
20.
Leo A. Joyce Prof. James W. Canary Prof. Eric V. Anslyn 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(26):8064-8069
The association between an achiral copper(II)‐containing host 1 and chiral carboxylates has been expanded beyond previous studies to new chiral carboxylate guests, both α‐amino acids and β‐homoamino acids. The observed exciton‐coupled circular dichroism (ECCD) signals for the enantiomers of each carboxylate were equal and opposite, and these signals differed in size and shape between the individual amino acids. Linear discriminant analysis (LDA) was applied as a statistical analysis technique to differentiate the amino acids, both enantioselectively and chemoselectively, giving the absolute configuration and identity of the amino acid. The identity of each of the α‐amino acids and β‐homoamino acids were determined independently by LDA, and then the two were considered together. Each of these analyses showed good differentiation of the amino acid guests with the use of only one host molecule. 相似文献