Academic literature on the topic 'Α stereoselectivity'

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Journal articles on the topic "Α stereoselectivity"

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Ross, Günther, та Ivar Ugi. "Stereoselective syntheses of α-amino acid and peptide derivatives by the U-4CR of 5-desoxy-5-thio-D-xylopyranosylamine". Canadian Journal of Chemistry 79, № 12 (2001): 1934–39. http://dx.doi.org/10.1139/v01-186.

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Since 1961, the synthesis of α-amino acids derivatives by the four-component reaction of isocyanides (U-4CR) as a one-pot reaction has been developed. Only recently it was found that a variety of these α-amino acids compounds can be formed stereoselectively by the U-4CR using 1-amino-5-deoxy-5-thio-2,3,4-tri-O-isobutanoyl-β-D-xylopyranose as the amine component. The stereoselectivity inducing auxiliary 5-desoxy-5-thio-D-xylopyranosyl group of the so-formed products can be replaced selectively by hydrogen.Key words: stereoselective U-4CR, chiral amine component, amino carbohydrate, α-amino acid
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Štěpánek, Petr, Ondřej Vích, Lukáš Werner, Ladislav Kniežo, Hana Dvořáková та Pavel Vojtíšek. "Stereoselective Preparation of Precursors of α-C-(1→3)-Disaccharides". Collection of Czechoslovak Chemical Communications 70, № 9 (2005): 1411–28. http://dx.doi.org/10.1135/cccc20051411.

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The stereoselectivity of cycloaddition of sugar-containing substituted 1-(thiazol-2-yl)but-2-en-1-ones 1 and vinyl ethers was studied using the achiral vinyl ether/chiral catalyst as well as the chiral vinyl ether/achiral catalyst combinations. It has been shown that Eu(fod)3-catalyzed cycloaddition of oxadienes 1a-1e with the chiral vinyl ethers 9 and 10 affords stereoselectively almost pure cycloadducts 11a-11e and 12a-12e, respectively. The obtained cycloadducts are suitable precursors for the synthesis of α-C-(1→3)-disaccharides, containing 2-deoxy-arabino-hexopyranose moiety of D- or L-co
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Veeraraghavan Ramachandran, P., та Barnabas Otoo. "Facile synthesis of 1-trifluoromethylalkenes via the decarboxylation of α-trifluoromethyl-β-lactones". Chemical Communications 51, № 62 (2015): 12388–90. http://dx.doi.org/10.1039/c5cc03230j.

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DCC-mediated cyclodehydration of α-trifluoromethyl-β-hydroxy acids provides α-trifluoromethylated β-lactone intermediates, without loss of stereoselectivity. These lactones undergo facile decarboxylation providing a simple route to obtain both alkyl and aryl 1-trifluoromethyl alkenes in excellent yields and stereoselectivity.
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Alex, Catherine, Satsawat Visansirikul, and Alexei V. Demchenko. "A versatile approach to the synthesis of mannosamine glycosides." Organic & Biomolecular Chemistry 18, no. 34 (2020): 6682–95. http://dx.doi.org/10.1039/d0ob01640c.

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Lutz-Wahl, Sabine, Peter Fischer, Claudia Schmidt-Dannert, Wolfgang Wohlleben, Bernhard Hauer та Rolf D. Schmid. "Stereo- and Regioselective Hydroxylation of α-Ionone by Streptomyces Strains". Applied and Environmental Microbiology 64, № 10 (1998): 3878–81. http://dx.doi.org/10.1128/aem.64.10.3878-3881.1998.

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ABSTRACT A total of 215 Streptomyces strains were screened for their capacity to regio- and stereoselectively hydroxylate β- and/or α-ionone to the respective 3-hydroxy derivatives. With β-ionone as the substrate, 15 strains showed little conversion to 4-hydroxy- and none showed conversion to the 3-hydroxy product as desired. Among these 15 Streptomyces strains, S. fradiae Tü27, S. arenae Tü 495, S. griseus ATCC 13273, S. violaceoniger Tü 38, and S. antibioticus Tü 4 and Tü 46 converted α-ionone to 3-hydroxy-α-ionone with significantly higher hydroxylation activity compared to that of β-i
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Levitskiy, Oleg A., Olga I. Aglamazova, Yuri K. Grishin та ін. "Solvent-triggered stereoselectivity of α,α-cyclopropanation of amino acids in the Ni(ii) chiral coordination environment". Dalton Transactions 49, № 25 (2020): 8636–44. http://dx.doi.org/10.1039/d0dt01578d.

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Unexpected solvent-controlled increase in stereoselectivity of glycine cyclopropanation within chiral Ni(ii) coordination environment was observed and rationalized. Cyclopropanated diastereomeric complexes exhibit stereodependent redox-activity.
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Nakamura, Shuichi, Ryota Yamaji та Masaru Iwanaga. "Enantioselective construction of imidazolines having vicinal tetra-substituted stereocenters by direct Mannich reaction of α-substituted α-isocyanoacetates with ketimines". Chemical Communications 52, № 47 (2016): 7462–65. http://dx.doi.org/10.1039/c6cc02911f.

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Lamothe, S., K. L. Cook, and T. H. Chan. "Chiral organosilicon compounds in synthesis. Preparation and stereoselective alkylations of silylcinnamyl carbanions." Canadian Journal of Chemistry 70, no. 6 (1992): 1733–42. http://dx.doi.org/10.1139/v92-217.

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Silylallyl carbanions of type 13 bearing a chiral lithium complexing substituent remote from silicon can be alkylated regio- and stereoselectively at the α-position by small electrophiles in nonpolar solvents. The regiochemical outcome of the reaction was found to be highly dependent on the size of the incoming electrophile. Secondary alkyl halides react preferentially at the γ-center and good levels of stereoselectivity are still obtained in nonpolar solvents despite the rather long distance between the reacting center and the chiral auxiliary. Transformation of the alkylated allylsilanes int
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Bueno, M. P., C. Cativiela, C. Finol, J. A. Mayoral та C. Jaime. "Diels–Alder reactions of methyl-N-acyl-α,β-dehydroalaninates with cyclopentadiene". Canadian Journal of Chemistry 65, № 9 (1987): 2182–86. http://dx.doi.org/10.1139/v87-365.

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A study has been made of the Diels–Alder reaction of methyl-N-acetyl (and benzoyl)-α,β-dehydroalaninates with cyclopentadiene. In the reaction of methyl-N-acetyl-α,β-dehydroalaninate total conversion is obtained under several conditions, while the N-benzoyl derivative shows a lower reactivity. The stereoselectivity of the reaction is determined by 1H nuclear magnetic resonance spectroscopy. Perturbation MO calculations, using wave functions generated by the MNDO method, are used to rationalize the relative reactivity of the dienophiles and the stereoselectivity observed.
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Te Koppele, J. M., B. Coles, B. Ketterer та G. J. Mulder. "Stereoselectivity of rat liver glutathione transferase isoenzymes for α-bromoisovaleric acid and α-bromoisovalerylurea enantiomers". Biochemical Journal 252, № 1 (1988): 137–42. http://dx.doi.org/10.1042/bj2520137.

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The stereoselectivity of purified rat GSH transferases towards alpha-bromoisovaleric acid (BI) and its amide derivative alpha-bromoisovalerylurea (BIU) was investigated. GSH transferase 2-2 was the only enzyme to catalyse the conjugation of BI and was selective for the (S)-enantiomer. The conjugation of (R)- and (S)-BIU was catalysed by the isoenzymes 2-2, 3-3 and 4-4. Transferase 1-1 was less active, and no catalytic activity was observed with transferase 7-7. Isoenzymes 1-1 and 2-2 of the Alpha multigene family preferentially catalysed the conjugation of the (S)-enantiomer of BIU (and BI), w
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Dissertations / Theses on the topic "Α stereoselectivity"

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Hu, Zhaoyu. "Préparation et oligomérisation d’une brique trisaccharidique issue de ressources renouvelables : vers la simplification d’un inhibiteur d’entrée du VIH ?" Thesis, Paris 11, 2013. http://www.theses.fr/2013PA112049.

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Ce travail de thèse a pour objectif la simplification de la préparation d’un nouveau type d’inhibiteur d’entrée du VIH conçu, synthétisé et validé dans le cadre d’une collaboration entre l’équipe de Glycochimie Moléculaire et Macromoléculaire dont je dépends, l’Institut de Biologie Structurale de Grenoble et l’Institut Pasteur de Paris. Ce prototype est constitué d’un mime fonctionnel de CD4 lié de façon covalente à un fragment dodécasaccharidique d’Héparane Sulfate dont la synthèse est complexe. Nous avons donc proposé de préparer des oligomaltosides sulfatés afin de déterminer s’ils pouvaien
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Lu, Yunyu. "Synthèse de mimes de fragments d'héparane sulfate pour les études de relation structure-activité sur un nouveau type d'inhibiteur d'entrée du VIH." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLS553/document.

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Ce travail de thèse a pour objectif la simplification de la préparation d’un nouveau type d’inhibiteur d’entrée du VIH conçu, synthétisé et validé dans le cadre d’une collaboration entre le laboratoire, l’Institut de Biologie Structurale de Grenoble et l’Institut Pasteur de Paris. Ce prototype est constitué d’un mime fonctionnel de CD4 lié de façon covalente à un fragment dodécasaccharidique d’Héparane Sulfate dont la synthèse est complexe. Nous avons donc proposé de préparer des oligomaltosides sulfatés afin de déterminer si ils pouvaient se comporter comme des mimes d’Héparane Sulfate. Dans
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Lai, Ping Shan. "Applications of α-Keto Carbocations in Carbon-Carbon and Carbon-Nitrogen Bond Formation". Thesis, 2011. http://hdl.handle.net/1807/32798.

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This thesis describes synthetic applications of α-keto carbocations, which represent potentially useful, but poorly studied, reversed polarity equivalents of enolates. In the first chapter, a Ag(I) – mediated method for the nucleophilic displacement of α-halocarbonyl compounds to construct carbon-carbon bonds is described. The highly electrophilic nature of the putative α-keto carbocation intermediates enables the use of relatively unreactive nucleophiles in both intra- and intermolecular contexts. Such intermediates also present interesting opportunities for stereocontrol: our efforts to carr
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Lin, Chiu-Ya, та 林秋雅. "(1) Concise Synthesis of Ganglioside Hp-s1 Analogue Neu5Ac α(2→6)Man β(1→1)Cer (2) Study of Stereoselectivity of Sialic Acid Donors". Thesis, 2016. http://ndltd.ncl.edu.tw/handle/18898965558562355808.

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碩士<br>國立中興大學<br>化學系所<br>104<br>Ganglioside Hp-s1 2 has better neuritogenic activity than GM1 in rat pheochromocytoma 12 cells. In order to explore the roles of glucosyl moiety of Hp-s1 in neurology, we have designed and synthesized new analogues (2a-2f). The glucosyl moiety was replaced with α-glucose, α-galactose, β-galactose, α- mannose, and β-mannose and their biological activities on SHSY5Y cells and natural killer T (NKT) cells were evaluated. In the first part of this thesis, we are focused on the synthesis of ganglioside Hp-s1 analogue Neu5Ac α(2→6)Man β(1→1)Cer 2f. Controlling the
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Book chapters on the topic "Α stereoselectivity"

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Lambert, Tristan H. "Construction of Stereochemical Arrays." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0045.

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The unprecedented enantioselective 1,8-addition of azlactone 1 to acylpyrrole 2 catalyzed by triaminophosphorane 3 was reported (J. Am. Chem. Soc. 2012, 134, 19370) by Takashi Ooi at Nagoya University. Tomislav Rovis at Colorado State University developed (Angew. Chem. Int. Ed. 2012, 51, 12330) the asymmetric oxidative hetero-Diels-Alder reaction of propionaldehyde (5) and ketone 6 to produce lactone 8, catalyzed by NHC catalyst 7 in the presence of phenazine. A related NHC catalyst 11 was utilized (Angew. Chem. Int. Ed. 2012, 51, 8276) by Xue-Wei Liu at Nanyang Technological University for the homoenolate addition of enal 9 to nitrodiene 10 to furnish 12 with high ee. The vinylogous conjugate addition of butenolide 13 to 15 to produce 16 with exquisite stereoselectivity was accomplished (Angew. Chem. Int. Ed. 2012, 51, 10069) by Kuo-Wei Huang at KAUST, Choon-Hong Tan at Henan University and Nanyang Technological University, and Zhiyong Jiang at Henan University. The enantioselective production of lactone 18 was achieved (J. Am. Chem. Soc. 2012, 134, 20197) by Jeffrey S. Johnson at the University of North Carolina at Chapel Hill by dynamic kinetic resolution (DKR) of α-keto ester 17. A related DKR strategy was employed (Org. Lett. 2012, 14, 6334) by Brinton Seashore-Ludlow at the KTH Royal Institute of Technology and Peter Somfai at Lund University in Sweden and the University of Tartu in Estonia for hydrogenation of α-amino-β-ketoester 19 to furnish aminoalcohol 21 with high Shigeki Matsunaga and Motomu Kanai at the University of Tokyo developed (Angew. Chem. Int. Ed. 2012, 51, 10275) a unique strategy for the selective production of the cross-aldol adduct 24 by in situ generation of an aldehyde enolate from allyloxyborane 23 under rhodium catalysis. The highly diastereoselective construction of adduct 26 bearing two adjacent quaternary stereocenters by ketone allylation with allyl sulfide 25 was reported (Angew. Chem. Int. Ed. 2012, 51, 7263) by Takeshi Takeda at the Tokyo University of Agriculture and Technology. Wen-Hao Hu at East China Normal University reported (Nature Chem. 2012, 4, 733) the enantioselective three-component coupling of diazoester 27, N-benzylindole (28), and imine 29 to furnish 31 under the action of Rh2(OAc)4 and phosphoric acid 30.
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Griffith, Allison K., and Tristan H. Lambert. "Alkenes." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0027.

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The α-C–H functionalization of piperidine catalyzed by tantalum complex 1 to pro­duce amine 2 was developed (Org. Lett. 2013, 15, 2182) by Laurel L. Schafer at the University of British Columbia. An asymmetric diamination of diene 3 with diaziri­dine reagent 4 under palladium catalysis to furnish cyclic sulfamide 5 was developed (Org. Lett. 2013, 15, 796) by Yian Shi at Colorado State University. Enantioenriched β-fluoropiperdine 8 was prepared (Angew. Chem. Int. Ed. 2013, 52, 2469) via amino­fluorocyclization of 6 with hypervalent iodide 7, as reported by Cristina Nevado at the University of Zurich. Erick M. Carreira at ETH Zürich disclosed (J. Am. Chem. Soc. 2013, 135, 6814) a ruthenium-catalyzed hydrocarbamoylation of allylic formamide 9 to yield pyrrolidone 10. Hans-Günther Schmalz at the University of Köln disclosed (Angew. Chem. Int. Ed. 2013, 52, 1576) an asymmetric hydrocyanation of styrene 11 with Ni(cod)₂ and phosphine–phosphite ligand 12 to yield exclusively the branched cyanide 13. A simi­lar transformation of styrene 11 to the hydroxycarbonylated product 15 was catalyzed (Chem. Commun. 2013, 49, 3306) by palladium complex 14, as reported by Matthew L. Clarke at the University of St Andrews. Feng-Ling Qing at the Chinese Academy of Sciences found (Angew. Chem. Int. Ed. 2013, 52, 2198) that the hydrotrifluoromethylation of unactivated alkene 16 to 17 was catalyzed by silver nitrate. The same transformation was also reported (J. Am.Chem. Soc. 2013, 135, 2505) by Véronique Gouverneur at the University of Oxford using a ruthenium photocatalyst and the Umemoto reagent 18. Clark R. Landis at the University of Wisconsin, Madison reported (Angew. Chem. Int. Ed. 2013, 52, 1564) a one-pot asymmetric hydroformylation using 21 followed by Wittig olefination to transform alkene 19 into the γ-chiral α,β-unsaturated carbonyl compound 20. Debabrata Mati at the Indian Institute of Technology Bombay found (J. Am. Chem. Soc. 2013, 135, 3355) that alkene 22 could be nitrated stereoselectively with silver nitrite and TEMPO to form alkene 23. Damian W. Young at the Broad Institute disclosed (Org. Lett. 2013, 15, 1218) that a macrocyclic vinylsiloxane 24, which was synthesized via an E-selective ring clos­ing metathesis reaction, could be functionalized to make either E- or Z-alkenes, 25 and 26.
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