The reactivity of perbenzoylated thioglycosides with various thiol aglycons has been compared and quantified using competitive glycosylation experiments. Methyl 2,3,4-tri-O-benzyl-α-D-glucopyranoside was employed as acceptor and DMTST as a promoter. The reactivity was found, as expected, to depend on the electron donating properties of the aglycon. Hence, the most reactive donor, the cyclohexyl thioglycoside, was found to be about three times as reactive as the thioethyl glycoside, which in turn was twice as reactive as the thiomethyl donor. The thiophenyl donor was even less reactive, whereas p-halophenyl donors were inert under the glycosylation conditions used but could be activated using NISTfOH as promoter. Furthermore, it was found that galactosyl donors were three to four times more reactive than the corresponding glucosyl derivative. These results allowed the design of an orthogonal coupling between thioglycosides with the same protecting groups (benzoyls) but with different thiol aglycons. Key words: thioglycosides, orthogonal glycosylations, competititive glycosylations.
已苯酰化
硫代糖苷与不同
硫醇配基的反应性进行了比较和定量化,使用竞争性糖基化实验。甲基2,3,4-三-O-苄基-α-
D-葡萄糖吡喃糖苷被用作受体,
DMTST被用作
促进剂。如预期,发现反应性取决于
硫配基的电子给予性质。因此,最具反应性的供体环己
硫代糖苷发现比
硫乙基糖苷反应性高约三倍,后者又比
硫甲基供体反应性高出两倍。
硫苯供体反应性更低,而对p-卤苯供体在糖基化条件下是惰性的,但可以使用NIS-TfOH作为
促进剂激活。此外,发现半
乳糖供体比相应的
葡萄糖衍
生物反应性高三到四倍。这些结果为设计具有相同保护基(苯酰基)但具有不同
硫醇配基的
硫代糖苷之间的正交偶联提供了可能。关键词:
硫代糖苷,正交糖基化,竞争性糖基化。