Formation of beta-mannopyranosides of primary alcohols using the sulfoxide method
Formation of beta-mannopyranosides of primary alcohols using the sulfoxide method
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DOI：
10.1021/jo9606517
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发表时间：
1996-07-12
影响因子：
3.6
通讯作者：
Sun, SX
中科院分区：
文献类型：
--
作者：
Crich, D;Sun, SX
β-O-吡喃甘露糖苷键存在于N-连接糖蛋白的共同核心五糖中，1存在于各种甘露聚糖和鞘糖脂2以及脂多糖中，3可以说是最困难的糖苷键类型，自然界对合成化学家提出了挑战。4在经典的糖苷化方案中不利于β-甘露糖苷形成的空间和立体电子因素的强大组合促进了不太直接的途径的发展，主要是2-酮糖的还原，β-葡糖苷的转化，R-甘露糖苷的自由基端基异构体转化，吡喃糖的直接O-烷基化，通过合适的系链将糖苷配基预连接到甘露糖基供体的O-2位。9虽然已经通过这些方法中的几种成功地合成了寡糖，10但是将糖苷配基直接偶联到具有高β-选择性的简单吡喃甘露糖基供体的方案11仍然是非常理想的目标。在这里，我们提出了这样一种方法的初级糖基受体。
The β-O-mannopyranosidic bond, as present in the common core pentasaccharide of the N-linked glycoproteins, 1 in various mannans and glycosphingolipids2 and in lipopolysaccharides, 3 is arguably the most difficult type of glycosidic linkage with which nature has challenged the synthetic chemist. 4 The formidable combination of steric and stereoelectronic factors that weigh against formation of the β-mannoside in classical glycosidation protocols has prompted the development of less direct routes, principally reduction of 2-ulososes, 5 inversion of β-glucosides, 6 radical anomeric inversion of R-mannosides, 7 direct O-alkylation of pyranoses, 8 and, most successfully, preattachment of the aglycon by means of a suitable tether to the O-2 position of mannosyl donors. 9 While the successful synthesis of oligosaccharides has been achieved through several of these methods, 10 a protocol for the direct coupling of aglycons to simple mannopyranosyl donors with high β-selectivity11 remains a very desirable goal. Here, we present such a method for primary glycosyl acceptors.