Synthesis of arabinofuranose branched galactofuran tetrasaccharides, constituents of mycobacterial arabinogalactan
作者:Lucía Gandolfi-Donadío、Malena Santos、Rosa M. de Lederkremer、Carola Gallo-Rodriguez
DOI:10.1039/c0ob00989j
日期:——
Mycolyl-arabinogalactan (mAG) complex is a major component of the cell wall of Mycobacterium tuberculosis, the causative agent of tuberculosis disease. Due to the essentiality of the cell wall for mycobacterium viability, knowledge of the biosynthesis of the arabinogalactan is crucial for the development of new therapeutic agents. In this context, we have synthesized two new branched arabinogalactafuranose tetrasaccharides, decenyl β-D-Galf-(1→5)-β-D-Galf-(1→6)[α-D-Araf(1→5)]-β-D-Galf (1) and decenyl β-D-Galf-(1→6)-[α-D-Araf-(1→5)]-β-D-Galf-(1→5)-β-D-Galf (2), as interesting tools for arabinofuranosyl transferase studies. The aldonolactone strategy for the introduction of the internal D-Galf was employed, allowing the construction of oligosaccharides from the non-reducing to the reducing end. Moreover, a one-pot procedure was developed for the synthesis of trisaccharide lactone 21, precursor of 2, which involved a glycosylation-deprotection-glycosylation sequence, through the use of TMSOTf as catalyst of the trichloroacetimidate method as well as promoter of TBDMS deprotection.
麦角糖阿拉伯半乳糖(mAG)复合物是结核分枝杆菌(Mycobacterium tuberculosis)细胞壁的重要组成部分,该菌是结核病的致病因子。由于细胞壁对分枝杆菌的生存至关重要,因此了解阿拉伯半乳糖的生物合成对于开发新的治疗药物具有重要意义。在此背景下,我们合成了两种新的分支型阿拉伯半乳糖呋喃糖四糖,分别为十烯基 β-D-Galf-(1→5)-β-D-Galf-(1→6)[α-D-Araf(1→5)]-β-D-Galf (1) 和十烯基 β-D-Galf-(1→6)-[α-D-Araf-(1→5)]-β-D-Galf-(1→5)-β-D-Galf (2),作为阿拉伯呋喃糖基转移酶研究的有趣工具。采用了醇内酯策略引入内源性 D-Galf,使得可以从非还原端到还原端构建寡糖。此外,还开发了一种一锅法合成三糖内酯 21,它是 2 的前体,该方法涉及到糖苷化-去保护-糖苷化序列,采用 TMSOTf 作为三氯乙酰胺法的催化剂,以及 TBDMS 去保护的促进剂。