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首页> 外文期刊>Chemistry: A European journal >Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl_4
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Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl_4

机译：TiCl_4对酰化叠氮化物和苯甲酰化二糖的区域专一性化作用

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Chelation induced anomerisation is promoted when Lewis acids, such as TiCl_4 or SnCl_4, 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. TiCl_4 (2.5 equiv) 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.
机译：当路易斯酸（例如TiCl_4或SnCl_4）与吡喃糖环的氧原子和另一个位点配位时，会促进螯合诱导的异构化，从而引起内环裂解，并使异构化为更稳定的异构体。在这项研究中，证明了区域特异性的定点异构化。用TiCl_4（2.5当量）诱导15种反应性低的糖基叠氮化物和二糖底物的异构化，获得了高收率（> 75％）和立体选择性（α/β> 9：1）。实例包括吡喃葡萄糖醛酸，吡喃葡萄糖醛酸和甘露吡喃糖酸酯以及N-乙酰化吡喃葡萄糖醛酸和吡喃葡萄糖醛酸酯衍生物。包括在聚半乳糖醛酸中发现的具有α1→4键的二糖。发现苯甲酰化的糖的使用在二糖的异构化中是重要的，因为使相关的乙酰基保护的和2，3-碳酸酯保护的衍生物异构化的尝试是不成功的。

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