- Differentiation between chelate ring inversion and aryl rotation in a CF3-substituted phosphine-sulfonate palladium methyl complex
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The solution conformations and dynamic properties of the CF3-sbustituted (ortho-phosphinoarenesulfonate)Pd complexes (PO-CF3)PdMe(L) ([PO-CF3]- = 2-{(o-CF3-Ph)2P}-4-Me-benzenesulfonate, L = 2,6-lutidine (3), pyridine (4)) were studied by NMR spectroscopy, taking particular advantage of 31P-19F through-space couplings and 1H-1H and 1H-19F nuclear Overhauser effects. In CD2Cl2 solution in the temperature range of -80 to 20 °C, 3 adopts an exo2 conformation. One o-CF3-Ph ring is positioned such that the CF3 group points toward Pd (exo) and exhibits through-space 4JPF coupling. The other o-CF3-Ph ring is positioned such that the CF3 group points away from Pd (endo) and does not exhibit through-space 4JPF coupling, and the o-H lies in the deshielding region near an axial site of the Pd square plane and exhibits a low-field chemical shift (δ > 9). Complex 4 exists as a 2:1 mixture of exo2 and exo3 isomers in CD2Cl2 solution at -90 °C. In exo2-4, one CF3 group is exo and exhibits through-space 4JPF coupling, while the other CF3 group is endo and does not exhibit through-space 4JPF coupling. In exo3-4, both CF3 groups are exo and exhibit through-space 4JPF couplings. Complex 4 undergoes two dynamic processes: rotation of the axial o-CF3-Ph ring (AaR), which interconverts exo2-4 and exo3-4 (ΔG&dagger = 9.9(5) kcal/mol), and chelate ring inversion (RI), which permutes the axial and equatorial o-CF3-Ph rings (ΔG&dagger = 21(1) kcal/mol).
- Feng, Ge,Conley, Matthew P.,Jordan, Richard F.
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Read Online
- New preparation method of febuxostat intermediate
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The invention relates to a new preparation method of a febuxostat intermediate. The method includes: taking cheap 4-hydroxybenzaldehyde as an initial raw material, firstly preparing aldoxime from 4-hydroxybenzaldehyde and hydroxylamine hydrochloride, then adding a corresponding thio reagent, and preparing a compound 4-hydroxythiobenzamide (152A1-00) by Beckmann rearrangement reaction; utilizing one-pot process, adopting cheap 4-hydroxybenzaldehyde as an initial raw material, carrying out a series of reactions, and then performing cyclization with 2-halogenated ethyl acetoacetate to obtain ethyl 2-(4-hydroxyphenyl)-4-methyl-5-thiazolecarboxylate or different salt forms (152A2x) thereof; and using isobutyl sulfonate (152H1x) with more easily controllable quality to replace bromo-isobutane soas to prepare ethyl 2-(3-formyl-4-isobutoxyphenyl)-4-methyl-5-thiazolecarboxylate (152A4-00). In conclusion, the method provided by the invention is more beneficial to safe, simple and cost-efficientindustrial scale preparation of the febuxostat intermediate with higher purity.
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Paragraph 0094-0097; 0122-0124
(2020/03/06)
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- Development of Selective Steroid Inhibitors for the Glucose-6-phosphate Dehydrogenase from Trypanosoma cruzi
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Chagas disease is a parasitic infection affecting millions of people across Latin America, imposing a dramatic socioeconomic burden. Despite the availability of drugs, nifurtimox and benznidazole, lack of efficacy and incidence of side-effects prompt the identification of novel, efficient, and affordable drug candidates. To address this issue, one strategy could be probing the susceptibility of Trypanosoma parasites toward NADP-dependent enzyme inhibitors. Recently, steroids of the androstane group have been described as highly potent but nonselective inhibitors of parasitic glucose-6-phosphate dehydrogenase (G6PDH). In order to promote selectivity, we have synthesized and evaluated 26 steroid derivatives of epiandrosterone in enzymatic assays, whereby 17 compounds were shown to display moderate to high selectivity for T. cruzi over the human G6PDH. In addition, three compounds were effective in killing intracellular T. cruzi forms infecting rat cardiomyocytes. Altogether, this study provides new SAR data around G6PDH and further supports this target for treating Chagas disease.
- Fredo Naciuk, Fabrício,Do Nascimento Faria, Jéssica,Gonc?lves Eufrásio, Amanda,Torres Cordeiro, Artur,Bruder, Marjorie
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supporting information
p. 1250 - 1256
(2020/07/27)
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- Stereoselective synthesis of bioactive isosteviol derivatives as α-glucosidase inhibitors
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Considerable interest has been attracted in isosteviol and its derivatives because of their large variety of pharmacological activities. In this project, a series of novel compounds containing hydroxyl, hydroxymethyl group and heteroatom-containing frameworks fused with isosteviol structure were synthesized and evaluated as α-glucosidase inhibitors, aimed at clarifying the structure-activity correlation. The results indicated that these isosteviol derivatives were capable of inhibiting in vitro α-glucosidase with moderate to good activities. Among them, indole derivative 15b exhibited the highest activities and thus may be exploitable as a lead compound for the development of potent α-glucosidase inhibitors.
- Wu, Ya,Yang, Jing-Hua,Dai, Gui-Fu,Liu, Cong-Jun,Tian, Guo-Qiang,Ma, Wen-Yan,Tao, Jing-Chao
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experimental part
p. 1464 - 1473
(2009/09/05)
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- Stereocontrolled Preparation of (Z)-1,4-but-2-endiol Esters in Phase-Transfer Conditions
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Isomerically pure esters of (Z)-1,4-but-2-endiol are prepared, in satisfactory yields, under phase-transfer conditions.
- Malanga, C.,Pagliai, L.,Menicagli, R.
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p. 2821 - 2826
(2007/10/02)
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- Deamination via Nitrogen Derivatives of Sulfonic Acids: N-Alkyl-N-nitroso-4-toluenesulfonamides, N-Alkyl-N-nitro-4-toluenesulfonamides, and N-Alkyl-N'-(4-toluenesulfonyloxy)diimide N-Oxides
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The thermal decomposition of several N-alkyl-N-nitroso-4-toluenesulfonamides, N-alkyl-N-nitro-4-toluenesulfonamides, and N-alkyl-N'-(4-toluenesulfonyloxy)diimide N-oxides was undertaken to determine whether the basicity of the negatively charged counterion in deamination reactions was a reaction variable.The nitrososulfonamides decompose following first-order kinetics to give the corresponding esters with retention of configuration.The reaction characteristics are very similar to those of the N-nitrosocarboxamides, and the reaction mechanisms are presumably very similar also.The N-nitrosulfonamides required high temperatures for decomposition, and they gave an anomalous set of products: amide (by denitration) and olefins, but no nitrous oxide or toluenesulfonate esters.The N'-toluenesulfonoxydiimide N-oxides, isomeric to the nitrosulfonamides, proved to be surprisingly stable compounds; they decompose by first-order kinetics to yield the corresponding esters and nitrous oxide.
- White, Emil H.,Lewis, Charles P.,Ribi, Max A.,Ryan, Thomas J.
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p. 552 - 558
(2007/10/02)
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