Stereospecific β‐
<scp>l</scp>
‐Rhamnopyranosylation through an S
<sub>N</sub>
i‐Type Mechanism by Using Organoboron Reagents
作者:Nobuya Nishi、Kazuhiro Sueoka、Kiyoko Iijima、Ryuichi Sawa、Daisuke Takahashi、Kazunobu Toshima
DOI:10.1002/anie.201808045
日期:2018.10.15
Stereospecific β‐l‐rhamnopyranosylations were conducted using a 1,2‐anhydro‐l‐rhamnopyranose donor and mono‐ol or diol acceptors in the presence of a glycosyl‐acceptor‐derived borinic or boronic ester. Reactions proceeded smoothly to provide the corresponding β‐l‐rhamnopyranosides (β‐l‐Rhap) with complete stereoselectivity in moderate to high yields without any further additives under mild conditions
立体特异性β-升-rhamnopyranosylations使用1,2-脱水-进行升-rhamnopyranose供体和单醇或糖基-受体衍生的二取代硼酸或硼酸酯的存在下二醇受体。反应进行得很顺利,可以提供相应的β- 1-鼠李糖吡喃糖苷(β- 1- Rha p),在中等至高收率下具有完全的立体选择性,在温和条件下无需任何其他添加剂。使用13 C动力学同位素效应(KIE)测量和DFT计算的硼酸酯介导糖基化机理研究与一致的S N一致i机制具有爆炸的过渡状态。另外,本糖基化方法被成功地应用于三糖的合成,α-升-RHA p - (1,2)-β-升-RHA p - (1,4)-Glc p,衍生自肺炎链球菌血清型7B,7C和7D。