2,6-Disubstituted Benzoates As Neighboring Groups for Enhanced Diastereoselectivity in β-Galactosylation Reactions: Synthesis of β-1,3-Linked Oligogalactosides Related to Arabinogalactan Proteins
作者:Nathan W. McGill、Spencer J. Williams
DOI:10.1021/jo902100q
日期:2009.12.18
plagued with poor stereoselectivity and side reactions including orthoester formation and transesterification of the 2-O-acyl group from the donor to the acceptor. We have investigated the use of 2,6-disubstituted benzoyl groups as bulky neighboring groups on the glycosyl donor. A 2,4,6-trimethylbenzoyl group was found to be optimal and enabled the formation of the β-galactopyranose-1,3-β-galactopyranose
阿拉伯半乳聚糖蛋白(AGP)是植物糖蛋白,含有β-1,3-连接的半乳聚糖核心。使用各种2 - O-酰基保护的糖基供体合成β-吡喃半乳糖-1,3-β-吡喃半乳糖键一直困扰着不良的立体选择性和副反应,包括原酸酯形成和2- O的酯交换反应-从供体到受体的酰基。我们已经研究了使用2,6-二取代的苯甲酰基作为糖基供体上的大体积邻近基团。发现2,4,6-三甲基苯甲酰基是最佳的,能够形成与已解除武装的酯保护的受体的β-半乳糖吡喃糖-1,3-β-半乳糖吡喃糖键,抑制酯交换反应并减少原酸酯的形成,同时增强β-半乳糖基化反应的选择性。制备了一系列β-1,3-连接的寡半乳糖苷,并精制为新糖缀合物,用于研究AGP的生物合成和AGP结合蛋白。