contrast, simple alcohols afforded approximately 1:1 mixtures of 2,3,4,6-tetra-O-acetyl, and 3,4,6-tri-O-acetyl 1,2-cis-glycosides due to anomerization and/or acid-catalyzed fragmentation of 1,2-orthoester intermediates. After reacetylation or deacetylation, acetylated or fully deprotected 1,2-cis-glycosides (alpha-D-gluco, alpha-D-galacto) were obtained in approximately 90% yields by a simple and direct
与SnCl(4)和CF(3)CO(2)Ag的
过乙酸糖(
D-葡萄糖,
D-半乳糖)的糖基化导致产生1,2-顺式或1,2-反式-糖苷,主要取决于使用的
酒精。特别地,由酰基保护的糖基供体预期的1,2-反式-糖苷以高收率与共享特定特征(例如庞大,吸电子基团或聚乙氧基基序)的醇形成。相比之下,由于异构化和//,简单的醇可提供约1:1的2,3,4,6-四-O-乙酰基和3,4,6-三-O-乙酰基1,2-顺式-糖苷的混合物或酸催化的1,2-原酸酯中间体的裂解。在重新乙酰化或脱乙酰化之后,通过简单和直接的方法以约90%的产率获得了乙酰化或完全脱保护的1,2-顺式-糖苷(α-
D-葡萄糖,α-
D-半乳糖)。