- Catalyst-free green synthesis and study of antioxidant activity of new pyrazole derivatives
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In this research, a novel procedure for the synthesis of pyrazole derivatives in excellent yields was studied using catalyst-free multicomponent reaction of isoquinoline, activated acetylenic compounds, alkyl bromides, triphenylphosphine and hydrazine in
- Tabarsaei, Navisa,Hamedani, Naghmeh Faal,Shafiee, Shahin,Khandan, Samira,Hossaini, Zinatossadat
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- ENANTIOSPECIFIC SYNTHESES OF 3,4-DIDEOXY-OCT-2-ULOSONIC ACIDS
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Ethyl 5,6,7,8-tetra-O-acetyl-3,4-dideoxy-D-arabino-oct-2-ulosonate and ethyl 3,4-dideoxy-5,6:7,8-di-O-isopropylidene-D-arabino-oct-2-ulosonate have been synthesised from peracetylated and bisacetonated aldehydo-D-arabinose respectively by a two stage proc
- Shing, Tony K. M.
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- Direct asymmetric Michael reactions of cyclic 1,3-dicarbonyl compounds and enamines catalyzed by chiral bisoxazoline-copper(II) complexes
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The catalytic direct Michael addition of cyclic 1,3-dicarbonyl compounds and enamines to unsaturated 2-ketoesters is presented. A series of different 4-hydroxycoumarins, 4-hydroxy-6-methyl-2-pyrone, 3-hydroxy-1H-phenalene-1-one, 2-hydroxy-1,4-naphthoquinone, 5,5-dimethyl-1,3-cyclohexanedione, and various enamines of cyclic 1,3-diketones all add to unsaturated 4-substituted 2-ketoesters in an enantioselective manner. The reaction is catalyzed by chiral bisoxazoline - copper-(II) complexes and proceeds in the absence of base to afford Michael adducts in good to high yields and with up to 98% ee. The products formed are substructures found in skeletons of important biological and pharmaceutical molecules. The scope and potential of the new reaction are discussed as well as the mechanism for the catalytic enantioselective reaction.
- Halland, Nis,Velgaard, Thomas,Jorgensen, Karl Anker
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- Asymmetric synthesis of 9-alkyl tetrahydroxanthenones: Via tandem asymmetric Michael/cyclization promoted by chiral phosphoric acid
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A tandem asymmetric Michael-addition/cyclization of cyclic 1,3-dicarbonyl compounds to β,γ-unsaturated α-ketoesters catalyzed by chiral phosphoric acid is presented. This protocol provides a facile approach for the construction of enantioenriched 9-alkyl tetrahydroxanthenones, an ubiquitous framework found in a number of natural products and pharmaceutical molecules, in high yields with good to high enantioselectivities. This journal is
- Gao, Yu-Qi,Hou, Yi,Chen, Junhan,Zhen, Yanxia,Xu, Dongyang,Zhang, Hongli,Wei, Hongbo,Xie, Weiqing
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supporting information
p. 348 - 354
(2021/01/29)
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- Metal-free michael-addition-initiated three-component reaction for the regioselective synthesis of highly functionalized pyridines: Scope, mechanistic investigations and applications
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A metal-free and completely regioselective three-component synthesis of highly functionalized pyridines from 1,3-dicarbonyl derivatives and Michael acceptors has been achieved. Activated Michael acceptors, that is, β,γ-unsaturated α-oxo carbonyl derivatives, were utilized, allowing substitution at the 4-position and remarkable functional diversity at the 2-position of the pyridine ring. The scope and limitations of this environmentally friendly domino reaction are disclosed, with full experimental data, and the results of mechanistic investigations are discussed. The three-component synthesis of polysubstituted pyridines starting from 1,3-dicarbonyl compounds, α,β-unsaturated carbonyl derivatives and ammonium acetate has been studied, including the scope and mechanism. This methodology is a rare example of a totally regioselective multicomponent access to highly substituted pyridines that complies with many of the stringent criteria of sustainable chemistry. Copyright
- Allais, Christophe,Lieby-Muller, Frederic,Rodriguez, Jean,Constantieux, Thierry
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supporting information
p. 4131 - 4145
(2013/07/19)
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- Development of α-keto-based inhibitors of cruzain, a cysteine protease implicated in Chagas disease
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Trypanosoma cruzi, a protozoan parasite, is the causative agent of Chagas disease, a major cause of cardiovascular disease in many Latin American countries. There is an urgent need to develop an improved therapy due to the toxicity of existing drugs and emerging drug resistance. Cruzain, the primary cysteine protease of T. cruzi, is essential for the survival of the parasite in host cells and therefore is an important target for the development of inhibitors as potential therapeutics. A novel series of α-ketoamide-, α-ketoacid-, α-ketoester-, and aldehyde-based inhibitors of cruzain has been developed. The inhibitors were identified by screening protease targeted small molecule libraries and systematically optimizing the P1, P2, P3, and P1′ residues using specific structure-guided methods. A total of 20 compounds displayed picomolar potency in in vitro assays and three inhibitors representing different α-keto-based inhibitor scaffolds demonstrated anti-trypanosomal activity in cell culture. A 2.3 A crystallographic structure of cruzain bound with one of the α-ketoester analogs is also reported. The structure and kinetic assay data illustrate the covalent binding, reversible inhibition mechanism of the inhibitor. Information on the compounds reported here will be useful in the development of new lead compounds as potential therapeutic agents for the treatment of Chagas disease and as biological probes to study the role that cruzain plays in the pathology. This study also demonstrates the validity of structure-guided approaches to focused library design and lead compound optimization.
- Choe, Youngchool,Brinen, Linda S.,Price, Mark S.,Engel, Juan C.,Lange, Meinolf,Grisostomi, Corinna,Weston, Scott G.,Pallai, Peter V.,Cheng, Hong,Hardy, Larry W.,Hartsough, David S.,McMakin, Marsha,Tilton, Robert F.,Baldino, Carmen M.,Craik, Charles S.
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p. 2141 - 2156
(2007/10/03)
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- Synthesis and Antiviral Activity of 2′-Deoxy-2′-fluoro-L-arabinofuranosyl 1,2,3-Triazole Derivatives
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The title compounds were prepared by building up the triazole ring at the anomeric position via the glycosyl azides 5 a,b. The anomeric configurations of these nucleosides were assigned by using 1H, 13C and NOESY NMR spectroscopy. Th
- Oelgen, Suereyya,Chu, Chung K.
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p. 804 - 811
(2007/10/03)
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- Simple syntheses of 3,4-dideoxy-oct-2-ulosonic acids
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Bisacetonated aldehydo-D-arabinose has been converted by three consecutive reactions (Wittig reaction, catalytic hydrogenation, and hydrolysis) into 3,4-dideoxy-D-arabino-oct-2-ulosonic acid (4-deoxy-KDO), isolated as its calcium sal
- Shing, Tony K. M.
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p. 1307 - 1308
(2007/10/02)
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- NAD(P)H MODELS 20 CHEMOSELECTIVE METAL ION CATALYZED REDUCTION OF α-KETO-β,γ-UNSATURATED ESTERS BY 1,4-DIHYDROPYRIDINE DERIVATIVES
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Ethyl 2-oxo-4-aryl-3-butene-1-oates (1a-c) are reduced by NAD(P)H models (1-n-propyl-1,4-dihydronicotinamide (4) and Hantzsch ester (5)), in presence of magnesium perchlorate.One equivalent of the reductant reduces the substrates selectively to the corresponding 2-oxo-4-arylbutanoates (6, 10a, b).An additional equivalent and higher temperature, converts ethyl 2-oxo-4-phenylbutanoate (6) to ethyl 2-hydroxy-4-phenylbutanoate (7).Reduction of ethyl 2-oxo-4-phenyl-3-buten-1-oate (1a) by Hantzsch ester in C2H5OD or by Hantzsch ester-4,4-d2 in C2H5OH, leads to direct transfer of the hydrogen or deuterium, respectively, without isotopic scrambling.These results have been interpreted to support the hydride transfer mechanism.
- Meijer, Louis H. P.,Pandit, Upendra K.
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p. 467 - 472
(2007/10/02)
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- NADH MODELS-19 CYCLOPROPANE RING AS A CHEMICAL PROBE IN THE STUDY OF THE MECHANISM OF HYDROGEN TRANSFER BY 1,4-DIHYDROPYRIDINE DERIVATIVES
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N-(Cyclopropylmethylene)phenylamines (1a-c), cyclopropyl 2-pyridyl ketones (5a-c) and ethyl cyclopropylmethylenepyruvate (14) have been subjected to reduction by 1,4-dihydropyridines in the presence of magnesium ions, and by tin hydrides.The reactions with 1,4-dihydropyridines do not involve cleavage of the three-membered ring in the reduction step.The observed acyclic product from 2-pyridyl 2,2-dimethylcyclopropyl ketone (5b) is a consequence of ring cleavage prior to reduction of the carbonyl function.In contrast, reduction of 1a-c and 5a-c by tin hydrides leads to products in which the cyclopropane moiety has undergone ring-opening.These findings support a hydride transfer mechanism for reductions with NADH models.
- Meijer, Louis H. P.,van Niel, Johannes C. G.,Pandit, Upendra K.
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p. 5185 - 5196
(2007/10/02)
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