Linear Total Synthetic Routes to β-<scp>d</scp>-<i>C</i>-(1,6)-Linked Oligoglucoses and Oligogalactoses up to Pentaoses by Iterative Wittig Olefination Assembly
作者:Alessandro Dondoni、Alberto Marra、Mamoru Mizuno、Pier Paolo Giovannini
DOI:10.1021/jo011142u
日期:2002.6.1
be seriously hampered by the 1,2-elimination of BnOH under the basic reaction conditions of the Wittig olefination, giving rise to the formation of substantial amounts of enopyranose. On the other hand, the ylide route B proved to be more efficient since very good yields (70-93%) of the isolated Wittig products were obtained throughout four consecutive cycles. Individual olefins and polyolefins obtained
遵循两个互补的途径A和B,用于通过亚甲基桥逐步迭代组装β-D-(1,6)-吡喃葡萄糖和吡喃半乳糖残基。在路线A中,结构单元由2,3,4-三-O-苄基-6-O-叔丁基二苯基甲硅烷基(O-TBDPS)β-连接的半乳糖基亚甲基磷烷组成,而在路线B中,结构单元由β-连接具有类似的正交保护羟基的甲酰基C-吡喃葡萄糖苷。在路线A中,每个循环由磷烷结构单元与在C-5碳原子上带有甲酰基的糖残基反应(偶联)和将O-TBDPS保护的伯醇转化为甲酰基组成(武装) 。因此,路线A定义为醛路线。另一方面,路线B中的每个循环都涉及糖醛结构单元与C-6处带有磷叶立德的底物的偶联,以及在准备步骤中引入磷基作为叶立德官能度的前体。因此,路线B被定义为伊利德路线。事实证明,在维蒂希烯化反应的基本反应条件下,BnOH的1,2-消除严重阻碍了方法A的效率,从而导致形成大量的烯吡喃糖。另一方面,叶立德途径B被证明是更有效的,因