Department of Chemistry, Binghamton University, Binghamton, New York 13902, United States.
J Org Chem. 2011 Jul 1;76(13):5207-18. doi: 10.1021/jo1025157. Epub 2011 May 27.
The stereoselectivity of glycosylation reactions is affected by many factors. Synthesis of 1,2-cis glycosidic linkages (such as α linkages in glucose and galactose like monosaccharides) is challenging due to lack of control of the stereoselectivity. Our systematic study of GalN(3) donors with different combination of protecting groups indicated that acetyl groups at the 3- and 4-positions are particularly important for high α-selectivity. Temperature is also recognized as a major factor in control of stereoselectivity. Mechanisms responsible for these experimental results are discussed and explored using computational methods. A remote participation model of the acetyl groups is proposed to explain the directing effects of the acetyl groups.
糖基化反应的立体选择性受多种因素影响。由于缺乏对立体选择性的控制，因此合成 1,2-顺式糖苷键（如葡萄糖和半乳糖中的α键）具有挑战性。我们对具有不同保护基组合的 GalN(3)供体进行了系统研究，结果表明 3-位和 4-位的乙酰基对于高α选择性非常重要。温度也是控制立体选择性的主要因素之一。使用计算方法讨论并探讨了这些实验结果的机制。提出了一个乙酰基的远程参与模型来解释乙酰基的引导效应。
