Crich David, Li Wenju, Li Hongmei
Department of Chemistry, University of Illinois, 845 West Taylor Street, Chicago, Illinois 60607-7061, USA.
J Am Chem Soc. 2004 Nov 24;126(46):15081-6. doi: 10.1021/ja0471931.
Two stereocontrolled syntheses of a methyl glycoside of an alternating beta-(1-->4)-beta-(1-->3)-mannohexaose, representative of the mannan from Rhodotorula glutinis, Rhodotorula mucilaginosa, and Leptospira biflexa, are described. Both syntheses employ a combination of 4,6-O-benzylidene- and 4,6-O-p-methoxybenzylidene acetal-protected donors to achieve stereocontrolled formation of the beta-mannoside linkage. The first synthesis is a linear one and proceeds with a high degree of stereocontrol throughout and an overall yield of 1.9%. The second synthesis, a block synthesis, makes use of the coupling of two trisaccharides, resulting in a shorter sequence and an overall yield of 4.4%, despite the poor selectivity in the key step.
本文描述了一种交替的β-(1→4)-β-(1→3)-甘露糖六糖甲基糖苷的两种立体控制合成方法，该六糖是红酵母、粘红酵母和双曲钩端螺旋体中甘露聚糖的代表。两种合成方法均采用4,6-O-亚苄基和4,6-O-对甲氧基亚苄基缩醛保护的供体组合，以实现β-甘露糖苷键的立体控制形成。第一种合成方法是线性合成，全程具有高度的立体控制，总产率为1.9%。第二种合成方法是片段合成，利用两个三糖的偶联，尽管关键步骤的选择性较差，但序列较短，总产率为4.4%。
