Stereoselective Synthesis of Allyl-<i>C</i>-mannosyl Compounds: Use of a Temporary Silicon Connection in Intramolecular Allylation Strategies with Allylsilanes
作者:Julien Beignet、James Tiernan、Chang H. Woo、Benson M. Kariuki、Liam R. Cox
DOI:10.1021/jo049061w
日期:2004.9.1
Methyl mannoside 16 containing an allyldimethylsilyl ether at C(2) was synthesized in nine steps from d-mannose. Reaction with TMSOTf in MeCN at room-temperature effected C-glycosylation to provide the α-allyl-C-mannosyl product 18 with excellent stereoselectivity. Crossover experiments over a range of reaction concentrations proved that reaction was proceeding via an intermolecular pathway rather
在9个步骤中,由d-甘露糖合成了在C(2)处含有烯丙基二甲基甲硅烷基醚的甲基甘露糖苷16。与将TMSOTf反应在MeCN在室温进行Ç -glycosylation以提供α烯丙基Ç -mannosyl产品18具有优异的立体选择性。在一系列反应浓度范围内的交叉实验证明,反应是通过分子间途径进行的,而不是通过分子内传递途径进行的。在存在除酸剂2,6-DTBMP的情况下,这种烯丙基化反应具有极高的立体选择性,这可归因于烯丙基甲硅烷基醚16表现为烯丙基化剂。七元环过渡态的几何约束解释了分子内烯丙基转移的缺乏。将改性的烯丙基硅烷29a - c连接到甲基甘露糖苷15的C(2)OH上可以改善物质。系留甘露糖苷27a - c的反应在室温下,在MeCN中存在2,6-DTBMP的条件下,使用TMSOTf提供的产物范围取决于甲硅烷基醚系链上烷基取代基的大小。不论甲硅烷基醚系链上烷基取代基的大小如何,二烯产物都是主