- 3-(1-Aminoalkyl)isoxazole-4-carboxylic acids as peptide bond replacements
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An orthogonally protected 3-(1-aminoalkyl)isoxazole-4-carboxylic acid has been prepared by 1,3-dipolar cycloaddition of a suitably protected α-aminonitrile oxide with an enaminoester dipolarophile; this protected amino acid has been deprotected and coupled independently at either the C- or N-terminus to produce pseudopeptide segments as peptide mimetics that contain a cis-amide bond replacement. Copyright (C) 2000 Elsevier Science Ltd.
- Jones, Raymond C. F.,Hollis, Stephen J.,Iley, James N.
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- Enamines as Surrogates of Alkene Carbanions for the Reductive Alkenylation of Secondary Amides: An Approach to Allylamines
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A new strategy to construct allylamines through reductive alkenylation of secondary amides with enamines is reported. The method features the use of trifluoromethanesulfonic anhydride as an activation reagent of amides, and enamines as unconventional alkenylation reagents. In this manner, enamines serve as surrogates of alkene carbanions instead of the classical enolates equivalents. A possible mechanism involving a Hoffmann-like elimination of the amine-borane complex intermediate is proposed.
- Wang, Ai-E,Yu, Cun-Cun,Chen, Ting-Ting,Liu, Yong-Peng,Huang, Pei-Qiang
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supporting information
p. 999 - 1002
(2018/02/23)
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- Lipid accumulation inhibitory activities of novel isoxazole-based chenodeoxycholic acids: Design, synthesis and preliminary mechanism study
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In continuation of our drug discovery program on hyperlipidemia, a series of novel isoxazole-chenodeoxycholic acid hybrids were designed, synthesized and evaluated for their lipid-lowering effects. Preliminary screening of all the synthesized compounds was done by using a 3T3-L1 adipocyte model, in which the most active compound 16b could significantly reduce the lipid accumulation up to 30.5% at a nontoxic concentration 10 μM. Further mechanism studies revealed that 16b blocked lipid accumulation via activating FXR-SHP signaling pathway, efficiently down-regulated the expression of key lipogenesis regulator SREBP-1c.
- Qiu, Rongmao,Luo, Guoshun,Li, Xinyu,Zheng, Fan,Li, Haolin,Zhang, Jin,You, Qidong,Xiang, Hua
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supporting information
p. 2879 - 2884
(2018/07/25)
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- Dual platinum and pyrrolidine catalysis in the direct alkylation of allylic alcohols: Selective synthesis of monoallylation products
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A dual platinum- and pyrrolidine-catalyzed direct allylic alkylation of allylic alcohols with various active methylene compounds to produce products with high monoallylation selectivity was developed. The use of pyrrolidine and acetic acid was essential, not only for preventing undesirable side reactions, but also for obtaining high monoallylation selectivity. Two cats are better than one: The combined use of platinum and pyrrolidine catalysts enabled the direct alkylation of allylic alcohols with reactive methylene compounds. Pyrrolidine was essential for obtaining high selectivity of the monoallylation products, which were produced without the use of excess nucleophiles. cod=1,5- cyclooctadiene, EWG=electron-withdrawing group.
- Shibuya, Ryozo,Lin, Lu,Nakahara, Yasuhito,Mashima, Kazushi,Ohshima, Takashi
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supporting information
p. 4377 - 4381
(2014/05/06)
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- Easily available nickel complexes as catalysts for the intermolecular hydroamination of alkenes and alkynes
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A series of nickel complexes of the type [(P-P)NiX2] ((P-P) = bisphospines or bisphosphites, X = chloride, triflate) were used as catalysts for the hydroamination of both activated and unactivated alkenes and alkynes with pyrrolidine. In general, the use of activated unsaturations, such as acrylonitrile, required mild reaction conditions (e.g. 100 °C and 4 h) in comparison with other non-activated alkenes. Particularly with a series of alkynes, the use of nickel(ii) centers diminished or even inhibited the formation of otherwise undesired homocoupling and/or transfer hydrogenation by-products, such as the ones obtained in the presence of zerovalent nickel. When using less activated substrates, better selectivity was obtained, although harsher reaction conditions were needed. From a general perspective, the results of this report strongly support the potential use of nickel as a good candidate for further application in the hydroamination of organic unsaturations by means of screening of several π acceptor ligands. The Royal Society of Chemistry.
- Reyes-Sanchez, Adan,Garcia-Ventura, Ilnett,Garcia, Juventino J.
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p. 1762 - 1768
(2014/01/06)
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- New methodologies for the synthesis of 3-acylpyridone metabolites
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A core isoxazolo[4,3-c]pyridin-4-one scaffold is prepared and elaborated at C-3(Me) and C-7 as a masked building block for 3-acylpyridin-2-ones related to the acylpyridone natural products Georg Thieme Verlag Stuttgart.
- Jones, Raymond C.F.,Choudhury, Abdul K.,Iley, James N.,Loizou, Georgia,Lumley, Christopher,McKee, Vickie
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body text
p. 654 - 658
(2010/10/01)
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- Tertiary 3-aminopropenones and 3-aminopropenoates: Their preparation, with and without Lewis acids, from secondary amines and 1,3-diketo compounds
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A direct method for the preparation of tertiary 3-aminopropenones and 3-aminopropenoates from β-diketones and β-keto esters, and secondary amines has been developed. The reaction is performed without solvent in the presence or absence of Lewis acid as catalyst, depending on the reactivity of both the amine and the diketo substrate. Georg Thieme Verlag Stuttgart.
- Vohra, Ramandeep Kaur,Renaud, Jean-Luc,Bruneau, Christian
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p. 731 - 738
(2008/01/03)
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- Reduction of carbonyl compounds using the carbonyl reductase of kluyveromyces marxianus
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A compound represented by a genera formula (Ia) or (Ib) and a stereo-selective preparation method thereof using a carbonyl reductase which is separated from Kluyveromyces marxianus. The compound can be prepared by reduction of substituted β-keto ester and can be used as an intermediate in preparing β-lactam group antibiotics.
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- 1,3-Dipolar cycloaddition route to nitrogen heterocyclic triones
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1,3-Dipolar cycloaddition of nitrile oxides, formed in situ by dehydration of primary nitro compounds, with pyrrolidine enamines of protected γ- or δ-amino-β-keto esters affords isoxazole-4-carboxylates; these undergo lactam formation and N-O bond cleavage to afford 3-acyltetramic acids and 3-acyl-4-hydroxypyridin-2-ones.
- Jones, Raymond C. F.,Bhalay, Gurdip,Carter, Paul A.,Duller, Kathryn A. M.,Dunn, Stephen H.
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p. 765 - 776
(2007/10/03)
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- Easy access to α-amino β-oxo esters from β-enamino esters
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N-Substituted α-amino β-oxo esters have been obtained by amination of β-enamino esters with ethyl N-[(4-nitrobenzenesulphonyl)oxy]carbamate (NsONHCO2Et), in the absence of added bases. The use of optically active pyrrolidines with C2 symmetry as chiral auxiliaries induces diastereoselectivities up to 80%.
- Felice, Elena,Fioravanti, Stefania,Pellacani, Lucio,Tardella, Paolo A.
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p. 4413 - 4416
(2007/10/03)
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- An alternative isoxazole route to α-alkoxycarbonyl-β-diketones
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Cycloaddition of oxygen-functionalized nitrite oxides to the enamine from ethyl acetoacetate produces 4-ethoxycarbonyl-5-methylisoxazoles carrying a 3-tetrahydropyranyloxymethyl, 3-diethoxymethyl or 3-ethoxycarbonyl substituent; the 3-formylisoxazole is prepared from the former two and condensed in situ with phosphoranes to give 3-alkenylisoxazoles that are cleaved by hexacarbonylmolybdenum or hydrogenolysis to afford α-alkoxycarbonyl-β-diketones.
- Jones, Raymond C. F.,Dunn, Stephen H.,Duller, Kathryn A. M.
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p. 1319 - 1321
(2007/10/03)
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- α-Cyclization of Tertiary Amines. Part 1.
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A general diastereoselective synthesis of functionalised pyrrolidine, indolizidine, pyrrolizidine and its seven-, eirgth-membered homologues is reported, starting from readily available enamine esters and acetylenedicarboxylate (DMAD).
- Jiang, Shuiping,Janousek, Zdenek,Viehe, Heinz G.
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p. 1185 - 1188
(2007/10/02)
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- An Isoxazole Route to Unsaturated α-Alkoxycarbonyl-β-diketones
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Cycloaddition of diethylphosphonomethyl nitrile oxide to the enamine from ethyl acetoacetate produces 4-ethoxycarbonyl-3-diethoxyphosphonylmethyl-5-methylisoxazole; condensation of the phosphonate with aldehydes and ketones gives 3-alkenylisoxazoles that are cleaved by hexacarbonylmolybdenum to afford unsaturated α-alkoxycarbonyl-β-diketones.
- Jones, Raymond C. F.,Bhalay, Gurdip,Carter, Paul A.
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p. 1715 - 1716
(2007/10/02)
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- The γ-alkylation of cyclic β-ketoesters via their enamine derivatives
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The γ-alkylation - functionalization of cyclic β-ketoesters via their enamine derivatives is discussed with particular emphasis on their preparation from β-ketoesters and their reaction with various electrophiles such as electrophilic olefins, halogenoids, anmd allylic and benzylic halides.Although the amine ring size does not appear to affect reactivity to a great extent, the reaction is very sensitive to β-ketoester ring size, with six-membered rings giving the best results.In the latter case the alkylation-functionalization is general and specific to the γ-position and therefore provides an important complement to the dianion and related methodologies.
- Gravel, Denis,Labelle, Marc
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p. 1874 - 1883
(2007/10/02)
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