A selective Sc(OTf)3-catalyzed trialkylsilyl ether to acetyl ester exchange reaction with β-l-idopyranoside and 3,4-O-isopropylidene-β-d-galactopyranoside derivatives
作者:Weijun Ke、Dennis M. Whitfield
DOI:10.1016/j.carres.2004.10.006
日期:2004.12
be selectively replaced by acetate by taking advantage of a trialkylsilyl-acetate exchange reaction catalyzed by Sc(OTf)3 in the presence of acetic anhydride. The high O-2 selectivity is shown for triethylsilyl (TES), tert-butyldimethylsilyl (TBS), and triisopropylsilyl (TIPS). The selective cleavage reaction only worked well for TES and TBS derivatives. A selection of silyl triflates and silyl chlorides
单糖结构单元的选择性甲硅烷基化可用于制备复杂的低聚糖。我们现在报告,二醇,甲基(二甲基甲硅烷基甲硅烷基3-O-新戊酰基-β-L-氨基吡喃基)尿酸酯,可以被三烷基甲硅烷基三氟甲磺酸酯在O-2位置选择性甲硅烷基化。在保护O-4之后,通过利用在乙酸酐存在下Sc(OTf)3催化的三烷基甲硅烷基乙酸酯交换反应,可以用乙酸酯选择性地取代O-2甲硅烷基。对于三乙基甲硅烷基(TES),叔丁基二甲基甲硅烷基(TBS)和三异丙基甲硅烷基(TIPS),显示出高的O-2选择性。选择性裂解反应仅适用于TES和TBS衍生物。选择的甲硅烷基三氟甲磺酸酯和甲硅烷基氯用作与3,4-O-异亚丙基-1-硫代-硫代-β-D-吡喃半乳糖苷的甲硅烷基化试剂。大多数情况下,甲硅烷基化以高收率提供了2,6-二-O-甲硅烷基化的产物。裂解反应的研究表明,只有主要的甲硅烷基化的保护基被乙酰基取代。该反应与多种甲硅烷基保护基一起起作用,但不适