共查询到20条相似文献,搜索用时 31 毫秒
1.
Yoshihito Ueno Miki Hirai Yoshiaki Kitamura Kazutoshi Kiuchi Yukio Kitade 《Tetrahedron》2008,64(49):11328-11334
Short interfering RNAs (siRNAs) containing P3′→N5′ phosphoramidate linkages were successfully synthesized by introducing 2′-deoxy-2′-fluororibonucleoside and 5′-amino-2′,5′-dideoxy-2′α-fluororibonucleoside in succession. It was found that the introduction of 5′-amino-2′,5′-dideoxy-2′α-fluororibonucleosides into siRNAs improved the nuclease-resistant properties of the siRNAs without loss of their silencing efficacy. 相似文献
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Cong-Bin JiYun-Lin Liu Zhong-Yan CaoYi-Yu Zhang Jian Zhou 《Tetrahedron letters》2011,52(46):6118-6121
Only 1 mol % of K3PO4 is efficient enough to catalyze the hydroxymethylation of α-substituted nitroacetates in good to excellent yield. Both aliphatic and aryl substituted nitroacetates work well under this reaction. The first catalytic asymmetric version of this reaction also reported that 10 mol % of cupreidine could catalyze this reaction up to 71% ee and 89% yield. Paraformaldehyde and formalin could both serve as the hydroxymethylation C1 unit. The synthetic application of products is also demonstrated. 相似文献
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Robert S. Jansen Hilde Rosing Jan H.M. Schellens Jos H. Beijnen 《Journal of chromatography. A》2009,1216(15):3168-3174
The development of a method for the separation of 2′-2′-difluorodeoxycytidine (gemcitabine, dFdC), 2′-2′-difluorodeoxyuridine (dFdU) and their mono-, di- and triphosphates using a porous graphitic carbon column (Hypercarb), without ion-pairing agent, is described. The retention of dFdC and dFdU could be controlled with an organic modifier (acetonitrile, CH3CN) and the retention of the anionic nucleotides with an eluting ion (bicarbonate). Separation of all analytes was achieved using a 0–25 mM ammonium bicarbonate gradient in CH3CN–H2O (15:85, v/v). Under these conditions, however, very long re-equilibration times were required. Injection of an acidic solution (100 μL 10% formic acid in H2O, v/v; 2.65 M) after running a gradient directly restored the separation capabilities of the column. Still, separation between the analytes slowly deteriorated over a period of months. These problems were solved by preconditioning the column with a pH buffered hydrogen peroxide (H2O2) solution (0.05% H2O2 in CH3CN–H2O (15:85, v/v), pH 4) before starting an analytical run. The oxidation of the stationary phase with H2O2 prevented its slow reduction, which most likely caused the decreasing retention times. The analytes were detected using tandem mass spectrometry. 相似文献
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《Tetrahedron: Asymmetry》2001,12(21):3047-3052
A study of the enantioselectivity exhibited by the lipase B from Candida antarctica in the transesterification of different α-substituted α-propylmethanols with vinyl acetate is shown. The best results are obtained when the large-sized (L) substituent of the alcohol is either a phenyl group or more especially a cyclohexyl group, although the reaction rates are lower than when linear or slightly branched groups are present. It is also found that ramification at the β-position of the L substituent has a deleterious effect on both lipase activity and enantioselectivity. Moreover, some α-substituted benzyl alcohols bearing medium-sized (M) substituents larger than an ethyl and smaller than a propyl group are resolved by means of this methodology with moderate-good enantioselectivities (E=46–57) and similar reaction rates. 相似文献
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A mild and efficient synthesis of 1-aryl-1-fluoroethenes from benzothiazolyl (aryl)fluoromethyl sulfones and paraformaldehyde, under DBU- or Cs(2)CO(3)-mediated conditions at room temperature, is described. A comparable diethyl fluoro(naphthalen-2-yl)methylphosphonate reagent does not react with paraformaldehyde under these mild conditions. The utility of the methodology for synthesis of terminal α-fluoroalkenes bearing electron-withdrawing functionalities is also shown. 相似文献
7.
Masato HigashinoNaoko Ikeda Tetsuro ShinadaKazuhiko Sakaguchi Yasufumi Ohfune 《Tetrahedron letters》2011,52(3):422-425
A novel silyl group-directed anti-SN2′ reaction of allylic alcohols under Mitsunobu reaction conditions is described. The Mitsunobu reaction of α-hydroxy-α-alkenylsilanes with a TBS or TIPS group gave the anti-SN2′ product, in which regio- and stereochemical outcomes of the reaction depended on the steric bulkiness of the silyl group. 相似文献
8.
Attila Takács 《Tetrahedron》2008,64(1):61-66
Highly reactive iodoalkenes (α-iodostyrene and α,α′-diiodo-1,4-divinylbenzene) were prepared and used as substrates in palladium-catalysed aminocarbonylation reaction. Regardless of the type of amine nucleophile the corresponding N-substituted phenylacrylamides have been formed chemoselectively in nearly quantitative yields. High isolated yields (up to 83%) have been achieved both with unfunctionalised simple amines and amino acid methyl esters under mild reaction conditions. 相似文献
9.
Albert Nguyen Van Nhien Cyrille Tomassi Christophe Len José Marco-Contelles 《Tetrahedron》2004,60(21):4709-4727
The carbanion-mediated sulfonamide cyclisations (CSIC protocols) of glyco-α-sulfonamidonitriles derived from readily available uloses 1A and 1B have been investigated using different bases (potassium carbonate, cesium carbonate, LDA and n-BuLi). As a result, a series of enantiomerically pure [1,2-O-isopropylidene-α-d-erythro (and α-d-ribo)furanose]-3-spiro-3′-(4′-amino-5′H-2′,3′-dihydroisothiazole-1′,1′-dioxide) derivatives have been prepared and isolated in good yields. 相似文献
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Xiaohan Chen Ran Zhao Ziqiang Liu Shutao Sun Yingang Ma Qingyun Liu Xia Sun Lei Liu 《中国化学快报》2021,32(7):2305-2308
Chiral α-substituted 1,3-dihydroisobenzofurans are key scaffolds in a number of bioactive natural products and synthetic pharmaceuticals. However, catalytic asymmetric approaches have been rarely developed. Here, a redox deracemization technology is adopted to address the catalytic asymmetric synthesis. A broad range of α-aryl substituted 1,3-dihydroisobenzofurans are effectively deracemized in high efficiency with excellent ee. α-Alkynyl substituted ethers were also compatible with the deracemization technology. 相似文献
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Vorobyeva DV Karimova NM Odinets IL Röschenthaler GV Osipov SN 《Organic & biomolecular chemistry》2011,9(21):7335-7342
A convenient strategy for the synthesis of isoxazole-containing α-CF(3)-substituted α-aminocarboxylates and α-aminophosphonates have been developed. The method is based on copper-catalyzed 1,3-dipolar cycloaddition of different aromatic nitrile oxides to functionalized acetylenes. 相似文献
14.
本文以4-甲基邻苯二甲酸酐为原料, 成功地合成了5,5′-二甲基-2,2′-二茚满-1,1′,3,3′-四酮(2). 通过元素分析、核磁共振、红外光谱及质谱等测试手段, 确定了化合物2的结构与存在形式, 通过ESR测试发现化合物2具有顺磁性. 相似文献
15.
T. I. Osipova A. V. Belyankin A. R. Khomutov Yu. N. Zhukov E. N. Khurs R. M. Khomutov 《Russian Chemical Bulletin》1996,45(11):2588-2591
The reaction of ketoximes with hypophosphorous acid resulted in previously unknown -substituted--aminophosphinic acids, which were oxidized into the corresponding -substituted--aminophosphonic acids.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2729–2732, November, 1996. 相似文献
16.
JC-1作为一种荧光探针,广泛应用于线粒体细胞膜的电位测定。本文以1,2,4-三氯-5-硝基苯为起始底物,经多步反应以18%的总收率获得JC-1。
相似文献
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An efficient synthetic method was developed for l-β-3′-C-cyano-2′,3′-unsaturated nucleosides and l-3′-C-cyano-3′-deoxyribonucleosides. The key intermediate 11 was obtained from l-xylose, from which a series of pyrimidine and purine nucleosides were prepared in high yield by the coupling of 11 and various silyl-protected bases in the presence of TMSOTf. These nucleosides were eliminated, followed by deprotecting to give l-β-3′-C-cyano-2′,3′-unsaturated nucleosides. When selectively deprotected by hydrazine hydrate in buffered acetic acid-pyridine followed by treatment with potassium carbonate in methanol, l-3′-C-cyano-3′-deoxyribonucleosides were obtained. The synthesized nucleosides were tested for anti-HIV activity. 相似文献
19.
《Tetrahedron: Asymmetry》1999,10(14):2703-2712
An asymmetric synthesis of an α-substituted serine derivative was achieved by employing PLE-catalyzed hydrolysis of a prochiral malonate derivative, and the absolute configuration of the hydrolyzed product was unambiguously determined by the X-ray analysis of a camphorsulfonic acid derivative. 相似文献
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《Tetrahedron letters》1998,39(32):5739-5742
Reaction of the title compounds with PhINSO2Ar (Ar = p-tolyl or p-nitrophenyl) in the presence of catalytic copper (II) triflate in acetonitrile gave the corresponding 2 and/or 3-substituted aziridine-2-carboxylates in generally good yields. The latter, on reaction with nucleophiles, gave α-substituted α- or β-amino acids depending on the pattern of substitution on the aziridine ring. 相似文献