- Oligoethylene glycols as highly efficient mutifunctional promoters for nucleophilic-substitution reactions
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Herein, we report the promising use of n-oligoethylene glycols (oligoEGs) as mutifunctional promoters for nucleophilic-substitution reactions employing alkali metal salts. Among the various oligoEGs tested, pentaethylene glycol (pentaEG) had the most efficient catalytic activity. In particular, when compared with other nucleophiles examined, a fluorine nucleophile generated from CsF was significantly activated by the pentaEG promoter. We also performed various facile nucleophilic-displacement reactions, such as the halogenation, acetoxylation, thioacetoxylation, nitrilation, and azidation of various substrates with potassium halides, acetate, thioacetate, cyanide, and sodium azide, respectively, in the presence of the pentaEG promoter. All of these reactions provided their desired products in excellent yields. Furthermore, the combination of pentaEG and a tert-alcohol medium showed tremendous efficiency in the nucleophilic-displacement reactions (fluorination and methoxylation) of base-sensitive substrates with basic nucleophiles (cesium fluoride and potassium methoxide, respectively). The catalytic role of oligoEGs was examined by quantum-chemical methods. The oxygen atoms in oligoEGs were found to act as Lewis bases on the metal cations to produce the "flexible" nucleophile, whereas the two terminal hydroxy (OH) groups acted as "anchors" to orientate the nucleophile and the substrate into an ideal configuration for the reaction. The EG race: OligoEGs, such as pentaethylene glycol (pentaEG), act as mutifunctional promoters for nucleophilic-substitution reactions with the corresponding alkali-metal salts. The combination of pentaEG and a tert-alcohol media system showed tremendous efficiency in the fluorination and methoxylation of base-sensitive substrates by using the corresponding basic nucleophiles (see figure). Copyright
- Jadhav, Vinod H.,Jang, Seung Ho,Jeong, Hwan-Jeong,Lim, Seok Tae,Sohn, Myung-Hee,Kim, Ju-Young,Lee, Sungyul,Lee, Ji Woong,Song, Choong Eui,Kim, Dong Wook
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- Organocatalysis of nucleophilic substitution reactions by the combined effects of two promoters fused in a molecule: Oligoethylene glycol substituted imidazolium salts
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Oligoethylene glycol substituted imidazolium salts were synthesized as promoters for a range of SN2 reactions, and their efficiency was examined. These tailor-made organic promoters enhanced the nucleophilicity of alkali metal salts significantly through the combined effects of two promoters (oligoethylene glycols and imidazolium salts) in a single molecule. The effects of the oligoethylene glycol side chain length, ionic liquid anions, nucleophiles, and substrates were investigated systematically. [hexaEGmim][OMs] and [dihexaEGim][OMs] showed the highest efficiency for SN2 reactions using alkali metal salts. The role of the terminal hydroxyl groups of the oligoethylene glycol moiety was assessed by examining the relative S N2 yields of chlorination and bromination. The results showed that the hydrogen bonding strength of the hydroxyl groups with the nucleophile is very important. The mechanism for the excellent promotion of SN2 reactions by oligoEGILs was examined by quantum chemical calculations. The results showed that the oxygen atoms in the oligoethylene glycol portion and the ionic liquid anion act on the counter cation K+ or Na+ as a Lewis base, to enhance the reactivity of the metal salts significantly.
- Jadhav, Vinod H.,Kim, Ju-Young,Chi, Dae Yoon,Lee, Sungyul,Kim, Dong Wook
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- Synthesis, characterization, cytotoxic and antitubercular activities of new gold(I) and gold(III) complexes containing ligands derived from carbohydrates
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Novel gold(I) and gold(III) complexes containing derivatives of d-galactose, d-ribose and d-glucono-1,5-lactone as ligands were synthesized and characterized by IR, 1H, and 13C NMR, high resolution mass spectra and cyclic voltammetry. The compounds were evaluated in vitro for their cytotoxicity against three types of tumor cells: cervical carcinoma (HeLa) breast adenocarcinoma (MCF-7) and glioblastoma (MO59J) and one non-tumor cell line: human lung fibroblasts (GM07492A). Their antitubercular activity was evaluated as well expressed as the minimum inhibitory concentration (MIC90) in μg/mL. In general, the gold(I) complexes were more active than gold(III) complexes, for example, the gold(I) complex (1) was about 8.8 times and 7.6 times more cytotoxic than gold(III) complex (8) in MO59J and MCF-7 cells, respectively. Ribose and alkyl phosphine derivative complexes were more active than galactose and aryl phosphine complexes. The presence of a thiazolidine ring did not improve the cytotoxicity. The study of the cytotoxic activity revealed effective antitumor activities for the gold(I) complexes, being more active than cisplatin in all the tested tumor cell lines. Gold(I) compounds (1), (2), (3), (4) and (6) exhibited relevant antitubercular activity even when compared with first line drugs such as rifampicin.
- Chaves, Joana Darc Souza,Damasceno, Jaqueline Lopes,Paula, Marcela Cristina Ferreira,De Oliveira, Pollyanna Francielli,Azevedo, Gustavo Chevitarese,Matos, Renato Camargo,Louren?o, Maria Cristina S.,Tavares, Denise Crispim,Silva, Heveline,Fontes, Ana Paula Soares,De Almeida, Mauro Vieira
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- Synthesis and membranoprotective properties of new disulfides with monoterpene and carbohydrate fragments
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A cooxidation of carbohydrate and terpene thiols gives mixtures of disulfides containing 51 - 90% of the unsymmetric product. Membranoprotective and antioxidant properties of obtained unsymmetric and symmetric disulfides were evaluated based on their ability to inhibit the H2O2-induced hemolysis of erythrocytes, as well as the accumulation of secondary products of the peroxy oxidation of lipids and the oxidation of hemoglobin.
- Pestova,Izmestev,Shevchenko,Rubtsova,Kuchin
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p. 723 - 731
(2015/11/27)
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- Umpolung reactivity in the stereoselective synthesis of S-linked 2-deoxyglycosides
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Take control! An unprecedented sulfenylation of stereochemically defined 2-deoxyglycosyl lithium species with asymmetric sugar-derived disulfide acceptors enabled the stereoselective synthesis of both α- and β-S-linked 2-deoxyoligosaccharides. Reductive lithiation of 2-deoxyglycosyl phenylsulfides at -78°C provides predominantly axial glycosyl lithium species, which upon warming isomerize to predominantly equatorial lithium species (see scheme). Copyright
- Baryal, Kedar N.,Zhu, Danyang,Li, Xiaohua,Zhu, Jianglong
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supporting information
p. 8012 - 8016
(2013/08/23)
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- A novel tin-free procedure for alkyl radical reactions
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Desulfuration as a source of alkyl radicals: The addition of alkylsulfanyl radicals to isocyanides gives the corresponding alkyl radicals. This methodology can replace the usual tin-mediated radical procedures and allows for the generation of tertiary, secondary, and even nonstabilized primary radicals that can be used efficiently in reductive defunctionalizations and intermolecular additions to electron-rich olefins (see scheme).
- Benati, Luisa,Leardini, Rino,Minozzi, Matteo,Nanni, Daniele,Scialpi, Rosanna,Spagnolo, Piero,Strazzari, Samantha,Zanardi, Giuseppe
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p. 3598 - 3601
(2007/10/03)
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- Thiosugar nucleotide analogs: Synthesis of 5′-(2,3,4-tri-O-acetyl-6-S-acetyl-6-thio-α-D-galactopyranosyl diphosphate)
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The synthesis of a novel analog of uridine diphosphate galactose (UDP-Gal) is described. A sulfur atom was inserted into the 6-position of galactose to give uridine 5′-(2,3,4-tri-O-acetyl-6-S-acetyl-6-thio-α-D-galactopyranosyl diphosphate). This peracetylated thiol analogue of UDP-Gal has been synthesized in nine steps starting from methyl α-D-galactopyranoside in an overall yield of 3%.
- Elhalabi, Jordan,Rice, Kevin G.
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p. 1935 - 1940
(2007/10/03)
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