Regiospecific Anomerisation of Acylated Glycosyl Azides and Benzoylated Disaccharides by Using TiCl<sub>4</sub>
作者:Mark Farrell、Jian Zhou、Paul V. Murphy
DOI:10.1002/chem.201302572
日期:2013.10.25
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
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,从而导致内环裂解和异构化为更稳定的异构体。在这项研究中,证明了区域特异性定点异构化。的TiCl 4(2.5当量)用于诱导15种反应性低的糖基叠氮化物和二糖底物的异构化,并获得高产率(> 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醛酸酯以及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。已发现使用苯甲酰化的糖类在二糖异构化中非常重要,因为尝试使相关的乙酰基保护的2,3-碳酸酯保护的衍生物异构化的尝试并不成功。