- Synthesis of a model trisaccharide for studying the interplay between the anti α-Gal antibody and the trans-sialidase reactions in Trypanosoma cruzi
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Trypanosoma cruzi, the etiologic agent of Chagas disease, is covered by a dense glycocalix mainly composed by glycoproteins called mucins which are also the acceptors of sialic acid in a reaction catalyzed by a trans-sialidase (TcTS). Sialylation of trypo
- Giorgi, M. Eugenia,Lopez, Rosana,Agusti, Rosalia,Marino, Carla,de Lederkremer, Rosa M.
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Read Online
- Using DMF as Both a Catalyst and Cosolvent for the Regioselective Silylation of Polyols and Diols
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Highly regioselective silylation of primary hydroxyl groups of unprotected polyols and diols was obtained by the use of a mixed solvent of MeCN/DMF (10:1) in this study. DMF was discovered to be a good catalyst in this reaction, although the silylation us
- Lv, Jian,Luo, Tao,Zou, Dapeng,Dong, Hai
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p. 6383 - 6395
(2019/11/05)
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- Synthesis and characterization of sulfated gal-β-1,3/4-GlcNAc disaccharides through consecutive protection/glycosylation steps
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We have developed an expeditious procedure to yield large amounts of orthogonally protected Gal-β1,3/4-GlcNAc, which allowed for the systematic introduction of a sulfate group onto the C3/C6 positions of Gal and/or the C6 position of GlcNAc. In particular
- Tu, Zhijay,Hsieh, Hsiao-Wu,Tsai, Chih-Ming,Hsu, Chia-Wei,Wang, Shy-Guey,Wu, Kuan-Jung,Lin, Kuo-I,Lin, Chun-Hung
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p. 1536 - 1550
(2013/07/26)
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- Regiospecific anomerisation of acylated glycosyl azides and benzoylated disaccharides by using TiCl4
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Chelation induced anomerisation is promoted when Lewis acids, such as TiCl4 or SnCl4, coordinate to the pyranose ring oxygen atom and another site, giving rise to endocyclic cleavage and isomerisation to the more stable anomer. In this research regiospecific site-directed anomerisation is demonstrated. TiCl4 (2.5equiv) was employed to induce anomerisation of 15 glycosyl azide and disaccharide substrates of low reactivity, and high yields (>75 %) and stereoselectivies (α/β>9:1) were achieved. The examples included glucopyranuronate, galactopyranuronate and mannopyranuronate as well as N-acetylated glucopyranuronate and galactopyranuronate derivatives. A disaccharide with the α1→4 linkage found in polygalacturonan was included. The use of benzoylated saccharides was found to be important in disaccharide anomerisation as attempts to isomerise related acetyl protected and 2,3-carbonate protected derivatives were not successful. Copyright
- Farrell, Mark,Zhou, Jian,Murphy, Paul V.
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p. 14836 - 14851
(2013/11/06)
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- Synthesis of the pentasaccharide moiety of thornasterside A
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The synthesis of the pentasaccharide moiety of thornasteroside A, the first asterosaponin isolated from starfish in 1978 has been achieved for the first time. Initially, a [3+2] convergent strategy was attempted, but the β(1→4) glycosidic linkage between
- Xiong, Junlong,Lu, Zhichao,Ding, Ning,Ren, Sumei,Li, Yingxia
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supporting information
p. 6158 - 6166
(2013/09/24)
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- Challenging deprotection steps during the synthesis of tetra- and pentasaccharide fragments of the LeaLex tumor-associated hexasaccharide antigen
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We report the convergent synthesis of two novel tetrasaccharide and two novel pentasaccharide fragments of the LeaLex TACA: the tetrasaccharides contain neither the galactose at the Lea nonreducing end nor the fucose at the Lex reducing end; the pentasaccharides only lack the galactose residue at the Lea nonreducing end. Two of the analogues were prepared as hexyl glycosides to be used in NMR experiments and as soluble inhibitors in binding studies and two as 6-aminohexyl glycosides to be conjugated to carrier proteins. Our strategy relied on stepwise extensions using excess monosaccharide glycosyl donors (trichloroacetimidates and thioglycosides) in sequential glycosylation reactions. The protecting groups were chosen to limit the number of deprotection steps required to obtain the final derivatives. While this strategy ensured that all glycosylation reactions proceeded in very good yields (70-84%), deprotection of the oligosaccharide intermediates was challenging. Global deprotection using Birch metal dissolving conditions did not remove the tert-butyldiphenylsilyl group, which indeed was incompatible with such reaction conditions. Attempts to remove the TBDPS with tetrabutylammonium fluoride was unsuccessful and led to a complex mixture of compounds that could not be separated. The desired hexyl and aminohexyl tetrasaccharides were finally obtained after four- and five-step deprotection sequences, respectively. Deprotection of the pentasaccharide intermediate to give the hexyl and aminohexyl analogues also led to unexpected results. Indeed, during Zemplén deacylation, a chloroacetamide chlorine atom was displaced by methoxide ions leading to the corresponding methoxyacetamide. Once the chloroacetamide was fully reduced to an acetamide the pentasaccharides were obtained in four and five steps, respectively.
- Guillemineau, Micka?l,Auzanneau, France-Isabelle
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p. 8864 - 8878
(2013/01/15)
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- An efficient and recyclable catalyst for the cleavage of tert-butyldiphenylsilyl ethers
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An efficient, chemoselective, and environment-friendly method for the deprotection of tert-butyldiphenylsilyl ethers mediated by triflic acid supported on silica gel is reported. A wide range of tert-butyldiphenylsilyl ethers derived from carbohydrate and saponin residues can be smoothly cleaved in the presence of various types of other protecting groups in good to excellent yields in acetonitrile. This heterogeneous reaction does not require aqueous workup, and the supported catalyst can be readily recycled.
- Yan, Shiqiang,Ding, Ning,Zhang, Wei,Wang, Peng,Li, Yingxia,Li, Ming
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experimental part
p. 6 - 20
(2012/07/13)
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- Structural establishment of polygalatenosides A and B by total synthesis
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The first total synthesis of polygalatenosides A (1) and B (2), originally isolated from the traditional Chinese medicine and reported as antidepressant agents, is described here. Glycosylation between thiogalactosyl donors 6 and 7 and 1-deoxyglucosyl acc
- Huang, Chih-Ming,Liu, Rai-Shung,Wu, Tian-Shung,Cheng, Wei-Chieh
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p. 2895 - 2898
(2008/09/21)
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- Reactivity-based one-pot synthesis of a Lewis Y carbohydrate hapten: A colon-rectal cancer antigen determinant
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The stereospecific synthesis of a tumor-related carbohydrate antigenic hapten, Lewis Y, from three basic building units 1 - 3 has been achieved by a reactivity-based one-pot strategy. RRV = relative reactivity value.
- Mong, Kwok-Kong T.,Wong, Chi-Huey
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p. 4087 - 4090
(2007/10/03)
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