Tetrahedron Asymmetry

A class of α-amino acids-derived multifunctional amidophosphane precatalysts: application to the highly enantio- and diastereoselective silver(I)-catalyzed 1,3-dipolar cycloaddition reaction ()
Publication date: Available online 22 June 2017 Source:Tetrahedron: Asymmetry Author(s): Yihui Hou, Zhipeng Zhou, Pingle Liu, Jiankang Wang, Qinglin Hou, Pushan Wen, Haifei Wang A class of multifunctional amidophosphanes derived from chiral α-amino acids have been developed with two amide bonds, a tertiary amine and a phosphine. In combination with Ag(I) salts, these amidophosphanes have been demonstrated as highly efficient multifunctional catalysts in the asymmetric 1,3-dipolar cycloaddition of azomethine ylides as well as the three-component reaction of the α-iminoesters in situ generated. Under optimal conditions, highly functionalized endo-8 pyrrolidines were obtained with good to excellent yields (up to 99% yield) and enantioselectivities (up to 98% ee). Graphical abstract image
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The synthesis of chiral tridentate ligands from l-proline and their application in the copper(II)-catalyzed enantioselective Henry reaction ()
Publication date: Available online 19 June 2017 Source:Tetrahedron: Asymmetry Author(s): Daqian Xu, Qiangsheng Sun, Zhengjun Quan, Wei Sun, Xicun Wang A series of chiral tridentate ligands derived from readily available enantiopure l-proline were designed and synthesized. The ligands together with Cu(OAc)2 were successfully used in asymmetric Henry reactions. Various structurally divergent aldehydes and nitromethane were converted into versatile β-nitro alcohols in MeOH at room temperature with very good yields (up to 85%) and enantioselectivities (up to 86%). Graphical abstract image
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Catalytic asymmetric syntheses of (−)-oudemanisin A and its diastereomer ()
Publication date: Available online 17 June 2017 Source:Tetrahedron: Asymmetry Author(s): Yun Zhou, Qinghua Bian, Pengfei Yang, Lifeng Wang, Shuoning Li, Xiao Sun, Mingan Wang, Min Wang, Jiangchun Zhong The first asymmetric catalytic synthesis of (−)-oudemanisin A 1a and its diastereomer 1b has been achieved. The key steps of our strategy involved the asymmetric alkynylation of an unsaturated aliphatic aldehyde catalyzed by Trost’s ProPhenol ligand, chemoselective oxidation of the olefinic diol, base-induced ring opening of the lactone, and acylation–alkylation of the ester. Graphical abstract image
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An efficient synthesis of the opioid analgesic (R)-phenampromide via an aziridinium ion ()
Publication date: Available online 17 June 2017 Source:Tetrahedron: Asymmetry Author(s): Mohammad Mujahid, Prashant Mujumdar, Murugesan Sasikumar, Shirish P. Deshmukh, Murugan Muthukrishnan A simple and efficient synthesis of the opioid analgesic agent (R)-phenampromide with high enantiopurity (>99% ee) via the formation of an aziridinium ion as a key step using commercially available starting material is described. Graphical abstract image
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Chloramphenicol base chemistry. Part 11:1 chloramphenicol base-derived thiourea-catalyzed enantioselective Michael addition of malononitrile to α,β-unsaturated ketones ()
Publication date: Available online 16 June 2017 Source:Tetrahedron: Asymmetry Author(s): Linjie Yan, Haifeng Wang, Fangjun Xiong, Yuan Tao, Yan Wu, Fener Chen The first chloramphenicol base-derived thiourea-catalyzed enantioselective Michael addition of malononitrile to α,β-unsaturated ketones is reported. The Michael adducts were obtained in good to excellent yields (up to 98% yield) and enantioselectivities (up to 94% ee). This reaction has a broad substrate scope to various α,β-unsaturated ketones. With this in mind, this methodology was successfully applied to the synthesis of a chiral piperidone, an advanced building block for dihydropyridinone P2X7 receptor antagonists. Graphical abstract image
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Editorial board ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Graphical contents list ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Contributors to this issue ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Asymmetric biosynthesis of intermediates of anti-HIV drugs ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Yiyuan Wang, Yingxiu Cao, Yuanxiu Li, Jiayu Jin, Jinliang Li, Hao Song Human immunodeficiency virus (HIV) infection is the fifth most common cause of death and many new HIV infections occur every year. The prevalence of HIV also seriously affects the quality of a patient’s life. More than forty anti-HIV drugs have been put into clinical uses, many of which are chiral molecules with multiple stereogenic centers, for example abacavir, lamivudine, zidovudine, stavudine, tenofovir, atazanavir. However, the chemical synthesis of these chiral intermediates have the disadvantages of low enantiomeric purity and complex synthetic steps. The benefits of asymmetric biosynthesis of chiral drugs include high enantiomeric excess (e.e.), good product selectivity, mild reaction conditions, and less side effects. The biosynthesis of the chiral intermediates of these anti-HIV drugs is thus particularly important. Herein, we review the different sources of enzymes and microbial cells for the asymmetric biosynthesis of the above chiral anti-HIV drug intermediates. We also review recent biotechnology progress in engineering these enzymes and microbial cells with improved biocatalytic activities, including enzyme and cell immobilization, surface display of enzymes, and directed evolution of enzymes. These biotechnology processes enable the efficient biosynthesis of these chiral intermediates, facilitating the industrial production of anti-HIV drugs with reduced costs. Graphical abstract image
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Synthesis of the enantiomers of (3Z,9Z)-cis-6,7-epoxy-3,9-octadecadiene, one of the major components of the sex pheromone of Ectropis oblique Prout ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Jie Yu, Feng Guo, Yun-Qiu Yang, Hui-Hui Gao, Ru-Yan Hou, Xiao-Chun Wan Both enantiomers of (3Z,9Z)-cis-6,7-epoxy-3,9-octadecadiene, one of which is the major component of the sex pheromone of Ectropis oblique Prout, were synthesized in 23% overall yield for the (−)-(6S,7R)-enantiomer and 18% yield for the (+)-(6R,7S)-isomer. This protocol uses a sequential regioselective ring-opening strategy and provides a convenient and reliable access to other structurally related insect sex pheromones. Preliminary biological studies revealed that (−)-(6S,7R)-2a was roughly as active as the natural pheromone, while racemic (±)-2 was less bioactive and (+)-2b was much less bioactive. Graphical abstract image
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2-Cyano-2-indolylpropanoic acid as a chiral derivatizing agent for the absolute configuration assignment of secondary alcohols and primary amines by 1H NMR and VCD ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Claudia I. Bautista-Hernández, Nayely Trejo-Carbajal, Erick A. Zúñiga-Estrada, Alberto Aristeo-Dominguez, Myriam Meléndez-Rodríguez, Oscar R. Suárez-Castillo, Maricruz Sánchez-Zavala, Julián Cruz-Borbolla, Martha S. Morales-Ríos, Pedro Joseph-Nathan A convenient approach for the absolute configuration assignment of secondary alcohols in the (8R,1′R,2′S,5′R)-15,25, (8S,1′R,2′S,5′R)-15,25, (8R,1′R)-21–24, and (8S,1′R)-21–24 ester series, and of primary amines in the (8R,1′R)-32–37 and (8S,1′R)-32–37 amide series, by means of 1H NMR and VCD spectroscopy, using 2-cyano-2-indolylpropanoic acid as a chiral derivatizing agent is presented. DFT calculations were carried out to demonstrate the anisotropic effect of the indole skeleton on the chiral alcohol or the amine fragment. Vibrational circular dichroism (VCD) measurements of the above series indicated a VCD bisignated couplet resulting from the interaction of the ester carbonyl group and the CN group. The absolute configuration assignments were further tested by X-ray diffraction analysis. Graphical abstract image
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Synthesis of [2.2]paracyclophane-based bidentate oxazoline–carbene ligands for the asymmetric 1,2-silylation of N-tosylaldimines ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Xichao Wang, Zhen Chen, Wenzeng Duan, Chun Song, Yudao Ma A series of novel oxazoline-substituted imidazolium salts with planar and central chirality has been successfully synthesized and applied to copper-catalyzed enantioselective 1,2-silylation of N-tosylaldimines. The oxazoline–carbene copper complex generated in situ by the reaction of the oxazoline-substituted imidazolium and Cu2O demonstrated an exceptionally high catalytic activity in the asymmetric 1,2-silylation of N-tosylaldimines, affording chiral α-amino silanes with excellent yields and enantioselectivities. Graphical abstract image
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Copper(II) complexes of 2-(pyridine-2-yl)imidazolidine-4-thione derivatives for asymmetric Henry reactions ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Gabriela Nováková, Pavel Drabina, Jan Svoboda, Miloš Sedlák The preparation of a new series of 2-(pyridine-2-yl)imidazolidine-4-thione derivatives is described. Their corresponding copper(II) complexes were found to be highly enantioselective catalysts for asymmetric Henry reactions (up to 98% ee). Immobilization of these complexes by anchoring onto Merrifield™ resin with respect to their use as recyclable catalysts was subsequently performed. The heterogeneous catalysts prepared in this way were tested in the asymmetric Henry reactions and showed high catalytic activity; they can be easily recycled, although their enantioselectivities were only moderate (∼50% ee). Graphical abstract image
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A convenient stereoselective synthesis of 5-hydroxy-3-oxoesters and 3-hydroxy-5-oxoesters ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Anna Żądło-Dobrowolska, Joerg H. Schrittwieser, Barbara Grischek, Dominik Koszelewski, Wolfgang Kroutil, Ryszard Ostaszewski A biocatalytic approach was employed for the asymmetric reduction of sterically demanding ketones to prepare 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates. Screening a collection of microorganisms led to the identification of stereocomplementary microbial strains that provide access to both enantiomers of 3-hydroxy-5-oxo-5-phenylpentanoates and 5-hydroxy-3-oxo-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). Moreover, the application of Saccharomyces cerevisiae gave two diastereomers of 3,5-dihydroxy-5-phenylpentanoates with high enantiomeric excess (up to 99% ee). The applicability of the identified strains was demonstrated by transforming the obtained dihydroxy ester into the chemically valuable lactone (4S,6R)-tetrahydro-4-hydroxy-6-phenyl-pyran-2-one. Graphical abstract image
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Stereoselective Michael-alkylation and Michael-oxidation reactions of chiral 1,3-dioxolanones ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Hao-Chun Liao, Kuan-Jen Yao, Yi-Chou Tsai, Biing-Jiun Uang A highly diastereoselective Michael-alkylation/oxidation methodology has been developed for the synthesis of optically active α-hydroxy-1,5-diester subunits. Inverse stereochemistry at the C2′ position could be achieved by using a Michael acceptor equipped with a suitable group followed by a highly stereoselective protonation. This methodology has been applied to the enantioselective synthesis of the upper fragment of (+)-retusine. Graphical abstract image
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Enzyme mediated kinetic resolution of δ-hydroxy-α,β-unsaturated esters as a route to optically active δ-lactones ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Dominik Koszelewski, Daniel Paprocki, Anna Brodzka, Ryszard Ostaszewski A novel synthetic route to optically active saturated and unsaturated δ-lactones based on enzymatic kinetic resolution and ring-closing metathesis reactions has been proposed. The influence of temperature, co-solvent, organic additives and the substrate structure on the catalytic behavior of selected hydrolases was studied. The substantial impact of the organic co-solvent and surfactant type on the enzymatic activity and enantioselectivity was observed providing enantiomerically pure δ-hydroxy-α,β-unsaturated esters. The established protocol combining enzymatic kinetic resolution with ring closing metathesis was successfully applied in the synthesis of the enantiomerically pure (6R)-phenyl-5,6-dihydro-2H-pyran-2-one which plays crucial role in the synthesis of the number of bioactive compounds. Graphical abstract image
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Study of a new ‘chiral proton’ organocatalyst with hydrolase activity: application in azlactone racemic dynamic resolution ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Ángel L. Fuentes de Arriba, Omayra H. Rubio, Luis Simón, Victoria Alcázar, Laura M. Monleón, Francisca Sanz, Joaquin R. Morán For the first time, a 1,3-ketoenol system is described as an acid catalyst with hydrolytic activity. The combination of an enol and a pyridine/benzimidazole supported on a benzofuran skeleton allowed the creation of a novel bifunctional organocatalyst, which has been applied in azlactone racemic dynamic resolution. In spite of the moderate enantioselectivities obtained, the catalyst constitutes a novel concept in the field of chiral Brønsted acid catalysis. Graphical abstract image
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A planar chiral six-membered cyclic (amino)(ferrocenyl)carbene and its sulfur adduct ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Risa Yasue, Masaru Miyauchi, Kazuhiro Yoshida A planar chiral ferrocene-fused cyclic aldimine was synthesized and a series of iminium salts were divergently prepared from it. The new carbene was generated from a salt by simple deprotonation with a strong base and identified by a carbene trapping experiment with sulfur. The sulfur adduct was fully characterized and its crystal structure implied that the new carbene would create an excellent chiral environment when used as a catalyst or a ligand in catalytic asymmetric synthesis. Graphical abstract image
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Conformationally rigid chiral ferrocene derivative: Synthesis, resolution and stereochemical assignment ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Kamsali Murali Mohan Achari, Chinnasamy Ramaraj Ramanathan A conformationally rigid chiral molecule LB-I with Lewis basic site has been designed and synthesized in racemic form from ferrocene via Lewis acid mediated diastereoselective cyclization of hydroxy lactam. Both isomers were successfully obtained in enantiomerically pure form through classical resolution using dibenzoyl-d-tartaric acid as the chiral resolving agent in acetone. The nature of the diastereomeric salt formed in the resolution process was investigated by single crystal X-ray crystallographic studies. The absolute configuration of (+)-LB-I was unambiguously assigned as (S,Rp ) by single crystal analysis of the salt I obtained from precipitate fraction containing (+)-LB-I and dibenzoyl-d-tartaric acid. Graphical abstract image
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A carbohydrate-derived trifunctional scaffold for DNA-encoded libraries ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Amalia M. Estévez, Felix Gruber, Alexander L. Satz, Rainer E. Martin, Hans Peter Wessel For the generation of DNA-encoded libraries, a central scaffold containing three exit vectors with defined chirality was devised starting from commercially available tri-O-acetyl-glucal. This scaffold may be connected to the DNA barcode at any of the three different exit vectors, thus making it a versatile approach as this readily leads to three different libraries. For one of the three possibilities, the compatibility with the DNA tag was demonstrated. The reactions include amide bond formation, Boc deprotection, urea formation, azide reduction and reductive alkylation. Graphical abstract image
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An improved synthesis of (20S)-camptothecin and its analogue via an asymmetric α-hydroxylation with a chiral organocatalyst ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6 Author(s): Xinlong Wang, Lingjun Xu, Fangjun Xiong, Yan Wu, Fener Chen An efficient and stereocontrolled synthesis of (20S)-camptothecin and an analogue has been developed. The key feature of this synthesis is the organocatalyzed asymmetric α-hydroxylation of the lactone precursor 4 to construct its stereocenter, providing tricyclic hydroxylactone 2 in 90% yield and with 88% enantioselectivity. The precursor 4 was efficiently synthesized from the known pyridine 5 in three steps. Graphical abstract image
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Stereochemistry abstracts ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Tetrahedron: Asymmetry Reports ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Cumulative author index ()
Publication date: 15 June 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 6
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Isoskeletomerism as an intermediate concept for mediating between stereoisomerism and isomerism. A remedy for conceptual defects of organic chemistry ()
Publication date: Available online 14 June 2017 Source:Tetrahedron: Asymmetry Author(s): Shinsaku Fujita After isoskeletomerism is introduced as an intermediate concept for mediating between stereoisomerism and isomerism, so-called ‘constitutional isomerism’ is critically discussed as one of the roots of confusion in organic chemistry. The convention that isomerism is subdivided into stereoisomerism and ‘constitutional isomerism’ is concluded to be misleading, because these concepts are conceptually distinct from a viewpoint of the concepts of equivalence relationships and equivalence classes. The indifference toward these concepts is one of the conceptual defects of organic chemistry. A new flowchart for judging enantiomerism, RS-stereoisomerism, stereoisomerism, isoskeletomerism, and isomerism is discussed to generate an isomer-classification diagram, where RS-stereoisomerism and isoskeletomerism are contained as new matters for remedying the conceptual defects. Skeletons are derived from basic skeletons by three operations (the bond operation, the replacement operation, and the substitutive operation), and they are used to examine the action of isoskeletomeric relationships. Equivalent molecular entities under an isoskeletomeric relationship are collected to give a set of isoskeletomers, which is concluded to be an equivalence class. The confusion caused by so-called ‘constitutional isomerism’ and its subcategories (‘skeletal isomerism’, ‘positional isomerism’, and so on) is critically discussed from the viewpoint of isoskeletomerism as a missing link. The double-entendre of the term constitution is examined when applied to both a 3D entity (a set of stereoisomers) and a 2D entity (a graph). Taxonomy of organic compounds and rational formulas, nomenclature of organic compounds, and combinatorial enumeration of chemical compounds are discussed from the viewpoint of isoskeletomerism. Graphical abstract image
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Advances on asymmetric organocatalytic 1,4-conjugate addition reactions in aqueous and semi-aqueous media ()
Publication date: Available online 12 June 2017 Source:Tetrahedron: Asymmetry Author(s): Anirban Mondal, Sudipto Bhowmick, Ayndrila Ghosh, Tanmoy Chanda, Kartick C. Bhowmick Asymmetric Michael addition reactions or 1,4-conjugate addition reactions are considered to be the fundamental C–C bond-forming reaction for the construction of chiral β-nitro, β-carbonyl and several other important structural motifs in organic synthesis. After the development of many chiral metal complexes as catalysts, a tremendous growth in the design and applications of variety of new chiral organocatalysts for asymmetric 1,4-conjugate addition reactions has been witnessed over the last two decades. Initially, asymmetric organocatalysis has been performed in organic solvents, but gradually performing the same catalysis in aqueous and semi-aqueous media became a necessity due to environmental aspects as well as to achieve better reactivity and selectivity. The structural and functional diversity of the chiral organocatalysts derived from natural and synthetic sources utilized differently the water either as the sole solvent, co-solvent or additive for optimising their best performances. In the present review, we discuss a detailed and comprehensive report on the advancement in the field of asymmetric organocatalytic 1,4-conjugate addition reactions in aqueous and semi-aqueous media. Graphical abstract image
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Catalytic asymmetric synthesis of β-triazolyl amino alcohols by asymmetric transfer hydrogenation of α-triazolyl amino alkanones ()
Publication date: Available online 12 June 2017 Source:Tetrahedron: Asymmetry Author(s): Vijyesh K. Vyas, Bhalchandra M. Bhanage The synthesis of optically active β-triazolyl amino alcohols was carried out via ruthenium catalyzed asymmetric transfer hydrogenation of α-triazolyl amino alkanones. This reaction proceeds under mild reaction conditions with up to 99% yield and 99.9% enantiomeric excess (ee). This protocol was applied to the synthesis of an enantiopure antitubercular agent and its arylated product with retention in enantiomeric purity. The absolute configuration at the stereogenic center of the chiral product as found to be (S). Graphical abstract image
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Recent advances in the enantioselective 1,3-dipolar cycloaddition of azomethine ylides and dipolarophiles ()
Publication date: Available online 5 June 2017 Source:Tetrahedron: Asymmetry Author(s): Bilel Bdiri, Boa-Jing Zhao, Zhi-Ming Zhou The synthesis of diastereo- and enantiopure heterocyclic molecules via catalytic asymmetric 1,3-dipolar cycloaddition reaction between azomethine ylides, generated in situ from α-amino acid-derived iminoesters and dipolarophiles is considered one of the most powerful and versatile techniques. In this review, we make a detailed overview of the latest developments in this area since 2014 and highlight the recent improvements in the structural scope of dipolarophiles, azomethine ylide precursors, and chiral ligands. Graphical abstract image
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Extractive biocatalysis in the asymmetric reduction of α-alkyl, β-aryl enones by Baker’s yeast ()
Publication date: Available online 3 June 2017 Source:Tetrahedron: Asymmetry Author(s): Rafaela M. Silva, Laura T. Okano, J. Augusto R. Rodrigues, Giuliano C. Clososki We prepared various chiral α-alkyl, β-aryl ketones with good to excellent enantiomeric excess through the Baker’s yeast asymmetric double-bond reduction of the corresponding α,β-unsaturated substrates adsorbed onto the resin Amberlite XAD-7. This methodology was compatible with substrates bearing both electron-donating and withdrawing groups attached to the aromatic ring. Elongation of the α-alkyl substituent of the starting material strongly affected the reactivity and enantioselectivity of the reaction. Graphical abstract image
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Chemo-enzymatic synthesis of (R)-5-hydroxymethyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate, a potential chiral building block for multicyclic terpenoids ()
Publication date: Available online 26 May 2017 Source:Tetrahedron: Asymmetry Author(s): Kazuaki Kuwata, Kengo Hanaya, Takeshi Sugai, Mitsuru Shoji The chemo-enzymatic synthesis of (R)-5-hydroxymethyl-2-isopropyl-5-methylcyclopent-1-en-1-yl trifluoromethylsulfonate, a potential chiral building block for polycyclic terpenoids containing a five–membered ring having isopropyl and angular methyl substituents, such as erinacin A and dolatriol, was achieved over 11 steps from ethyl 2-oxocyclopentane-1-carboxylate. The key synthetic precursor for this triflate was ethyl (1S,2R)-2-hydroxycyclopentanecarboxylate (>99% ee), which was prepared by a lipase-catalyzed enantioselective hydrolysis of the corresponding racemic acetate. The antipodal (S)-triflate is expected to be the synthetic intermediate for another group of terpenoids involving hamigeran B and stolonidiol. Enantiomerically pure (1R,2S)-hydroxyester (>99% ee) was prepared in high yield using the asymmetric reduction of the oxoester with commercially available carbonyl reductase, “Chiralscreen® OH”-E001. Graphical abstract image
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3-Menthoxybiphenyl-4-carboxylic acid: a versatile resolving agent and reagent for determination of the absolute configuration of benzylic alcohols ()
Publication date: Available online 26 May 2017 Source:Tetrahedron: Asymmetry Author(s): Shunsuke Kuwahara, Nobuyoshi Tasaki, Yuri Suzuki, Mizuki Nakagawa, Mari Ikeda, Yoichi Habata A versatile reagent for the chiral resolution and determination of the absolute configuration of benzylic alcohols, (−)-3-menthoxybiphenyl-4-carboxylic acid, is reported. (−)-3-menthoxybiphenyl-4-carboxylic acid was condensed with racemic benzylic alcohols to yield diastereomeric 3-menthoxybiphenyl-4-carboxylic esters, which were separated by reversed-phase HPLC. The absolute configurations of the 3-menthoxybiphenyl-4-carboxylic esters were unambiguously determined by exciton-coupled circular dichroism. Hydrolysis of the 3-menthoxybiphenyl-4-carboxylic esters yielded enantiopure alcohols, and their absolute configurations were simultaneously determined. Graphical abstract image
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Editorial board ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Graphical contents list ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Contributors to this issue ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Current applications of organocatalysts in asymmetric aldol reactions: An update ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5 Author(s): Majid M. Heravi, Vahideh Zadsirjan, Mahzad Dehghani, Nastaran Hosseintash The aldol reaction is one of the most important carbon–carbon bond formations in synthetic organic chemistry. An enantioselective aldol reaction should provide an enantioenriched product. The organocatalytic asymmetric aldol reaction via an in situ generated enamine intermediate is one of the most powerful synthetic tools to achieve enantiomerically pure products. This approach is often used to obtain chiral β-hydroxycarbonyl compounds with excellent enantioselectivity. In this report, we update our previous review regarding the applications of organocatalysts in asymmetric aldol reactions leading to chiral β-hydroxycarbonyl compounds as versatile synthetic motifs frequently found in pharmaceutically desired intermediates and biologically active naturally occurring compounds. Graphical abstract image
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Recent advances in asymmetric multicomponent reactions (AMCRs) ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5 Author(s): Tahereh Ahmadi, Ghodsi Mohammadi Ziarani, Parisa Gholamzadeh, Hoda Mollabagher Asymmetric multicomponent reactions (AMCRs) include the reaction of three or more reactants simultaneously to produce chiral products that they have some advantages containing simple procedures, saving time and energy, and being environmentally friendly processes. AMCRs have seen much development and their potent synthetic approaches are discussed in this review. Graphical abstract image
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Short syntheses of (−)-clavaminol A and deacetyl (+)-clavaminol H ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5 Author(s): Tian Jin, Lu Zhao, Maolin Huang, Yan Yue, Zhe-Bin Zheng, Won-Hun Ham Concise stereoselective syntheses of (−)-clavaminol A and deacetyl (+)-clavaminol H have been achieved from simple starting materials. Highlights of the synthesis for (−)-clavaminol A include a highly diastereoselective chelation-controlled hydride reduction of an amino ketone to give the anti amino alcohol directly, and NaBH4-mediated dehalogenation. The main synthetic approach for deacetyl (+)-clavaminol H features a highly diastereoselective chelation-controlled hydride reduction of the amino ketone to construct the anti amino alcohol and a palladium catalyzed hydrogenation reaction at the final step. Graphical abstract image
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Plant-mediated asymmetric reduction of 1-(3,4-dimethylphenyl)ethanone ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5 Author(s): Dubravko Pavoković, Renata Buđa, Fran Andrašec, Marin Roje, Marina Cvjetko Bubalo, Ivana Radojčić Redovniković Bioreduction mediated by plants is a highly selective and environmentally friendly approach to synthesise optically active alcohols. Herein the bioreduction of 1-(3,4)-dimethylphenyl)ethanone to the corresponding chiral alcohol 1-(3,4-dimethylphenyl)ethanol has been evaluated using nine different vegetables roots as biocatalysts. The chiral alcohol was prepared in yields ranging from 44.1% to 88.2%, and with enantiomeric excess up to 97.2% for the (S)-enantiomer. Sugar beet was the most promising among the tested vegetables roots. Therefore, sugar beet cell cultures (normal and transformed) were obtained and tested for the reduction as well, yielding the corresponding alcohol in the range from 62.1% to 88.2% yield and with enantiomeric excesses of >99%. Based on these results reported, there are no profound differences in the reductive capacity of undifferentiated cells and organs of the same plant species (sugar beet). Due to overall advantages of using cell cultures, we have highlighted this approach as a promising method for preparation of enantiomerically pure 1-(3,4-dimethylphenyl)ethanol. Graphical abstract image
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Resolution, absolute configuration and antifilarial activity of coumarinyl amino alcohols ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5 Author(s): Priyanka, Sweta Misra, Shailja Misra-Bhattacharya, Ray J. Butcher, Diksha Katiyar The resolution of racemic coumarinyl amino alcohols 5–10 was achieved by using the inexpensive and readily accessible chiral resolving agent N-carbethoxy-l-proline (S)-11. Direct esterification of rac-5–10 with (S)-11 furnished diastereomeric esters, which were easily separated by column chromatography. The obtained diastereomers yielded the desired enantiopure coumarinyl amino alcohols (S)-(+)-5–10 and (R)-(−)-5–10 in good yields with high enantiomeric excess on saponification. The absolute configurations were determined by X-ray crystal analysis and/or by comparison of the specific rotations. Furthermore, in in vitro antifilarial motility inhibition assays, enantiopure coumarins (S)-(+)-9, (R)-(−)-9 and (S)-(+)-10, (R)-(−)-10 were found to be less efficient in affecting the viability of macrofilariae of Brugia malayi than their racemic forms 9 and 10, respectively, indicating the synergistic effect of the enantiomers in evoking antifilarial action. Graphical abstract image
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Stereochemistry abstracts ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Tetrahedron: Asymmetry Reports ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Cumulative author index ()
Publication date: 15 May 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 5
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Editorial board ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4
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Graphical contents list ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4
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Contributors to this issue ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4
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A review on the synthetic approaches of rivaroxaban: An anticoagulant drug ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4 Author(s): Tanzeela Abdul Fattah, Aamer Saeed Rivaroxaban is an effective and potent oral anti-coagulant drug approved by US FDA in 2008 and is widely used in the treatment of thromboembolic ailments, deep venous thrombosis, pulmonary embolism, myocardial infarction, cerebral stroke, angina pectoris, and transitory ischemic attacks. This review comprehensively provides an overview of the various asymmetric synthetic methods employed for the synthesis of rivaroxaban in high yields and stereoselectivity describing the various chiral synthons used in the synthetic process along with pros and cons of each method. In addition, methods for the industrial production of rivaroxaban have been highlighted in the manuscript. Graphical abstract image
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Synthesis of chiral aza-bis(oxazolines) derived from (+)-camphor ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4 Author(s): Jaime González, Diego Martínez-Otero, Bernardo A. Frontana-Uribe, Erick Cuevas-Yañez Two novel chiral structurally azabis(oxazoline) ligands were synthesized using (+)-camphor as the starting material. Each of the ligands was prepared through the corresponding aminoalcohols. The structures of some crystalline derivatives were unambiguously established by X-ray analysis. Graphical abstract image
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Solvent free, fast and asymmetric Michael additions of ketones to nitroolefins using chiral pyrrolidine–pyridone conjugate bases as organocatalysts ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4 Author(s): Chandan K. Mahato, Mrinalkanti Kundu, Animesh Pramanik New chiral organocatalysts are envisaged based on a pyrrolidine–pyridone conjugate and synthesized from commercially available proline employing standard protocols. These catalysts were found to be useful for asymmetric Michael additions of ketones to nitroolefins to afford the desired products in very good yields (up to 98%) with excellent diastereo- and enantioselectivities (>97:3 syn/anti and up to 98% ee) in very short reaction time compared with the existing reports. Graphical abstract image
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Acylative kinetic resolution of racemic aromatic β-hydroxy esters catalyzed by chiral nucleophilic N-(1-arylethyl)benzoguanidines ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4 Author(s): Akira Yamada, Kenya Nakata, Isamu Shiina An efficient acylative kinetic resolution of racemic aromatic β-hydroxy esters with cyclohexanecarboxylic anhydride was achieved using newly designed (R)-N-methylbenzoguanidine ((R)-NMBG) derivatives. A series of (R)-NMBG derivatives was synthesized by modifying the original (R)-NMBG catalyst with the introduction of branched N-substituents containing a stereogenic center, and their catalytic performance was evaluated. (R,R)-N-(1-(β-1-Naphthyl)ethyl)benzoguanidine [(R,R)-NβNpEtBG] was found to function as an efficient acyl transfer catalyst for the reaction of a broad variety of substrates, regardless of the substituent type and substitution pattern. Graphical abstract image
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Pd-catalyzed enantioselective C–H arylation of phosphinamides with boronic acids for the synthesis of P-stereogenic compounds ()
Publication date: 15 April 2017 Source:Tetrahedron: Asymmetry, Volume 28, Issue 4 Author(s): Yuan-Hui Chen, Xu-Long Qin, Jing Guan, Zhi-Jun Du, Fu-She Han A Pd-catalyzed enantioselective C–H arylation of phosphinamides with aryl boronic acids is presented. With readily affordable amino acid derivatives as chiral ligands, the reaction proceeded efficiently to afford the P-stereogenic phosphinamides in up to 75% yield and with 99% ee under mild conditions. Most importantly, the reaction could be performed on a large scale for various substrates. This method provides an alternative and reliable way for accessing P-stereogenic phosphinamides. Graphical abstract image
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