Rapid, iterative assembly of octyl α-1,6-oligomannosides and their 6-deoxy equivalents
作者:Jacinta A. Watt、Spencer J. Williams
DOI:10.1039/b503919c
日期:——
Mycobacterium tuberculosis is the cause of the deadly human disease tuberculosis. In studies over the last 40 years it has been revealed that this organism possesses a complex cell wall including glycophospholipids such as the phosphatidylinositiol mannosides (PIMs), lipomannan (LM) and lipoarabinomannan (LAM). These glycolipids all contain a common α-1,6-linked mannoside core, and the higher PIMs and LAM possess α-1,2-linked mannosyl residues. It has been shown that simple α-1,6-linked oligomannosides can act as substrates for α-1,6-mannosyltransferases in mycobacteria. Here we report a simple iterative synthesis of a series of hydrophobic octyl α-1,6-linked oligomannosides from mono- through to tetrasaccharides. We have utilized a single thioglycoside donor and alcohol acceptor. Further, we have developed conditions for the conversion of each of these compounds to the 6-deoxy congeners. Deoxygenation of the 6-position of the terminal mannosyl residue should prevent these compounds acting as substrates for the abundant α-1,6-mannosyltransferases in mycobacteria and should permit detection of the elusive α-1,2-mannosyltransferase activity responsible for elaboration of LM to mature LAM and the biosynthesis of the higher PIMs.
结核分枝杆菌(Mycobacterium tuberculosis)是导致致命的人类疾病结核病的原因。在过去40年的研究中,已揭示这种微生物拥有一个复杂的细胞壁,其中包括糖磷脂类,如磷脂酰肌醇甘露醇(PIMs)、脂甘露醇(LM)和脂阿拉伯甘露醇(LAM)。这些糖脂都含有一个共同的α-1,6-链接的甘露糖核,而高级的PIMs和LAM则具有α-1,2-链接的甘露糖残基。已有研究表明,简单的α-1,6-链接的寡甘露糖可以作为分枝杆菌中α-1,6-甘露糖基转移酶的底物。在这里,我们报告了一种简单的迭代合成方法,用于制备一系列疏水的辛基α-1,6-链接的寡甘露糖,从单糖到四糖。我们使用了一个单一的硫代糖供体和醇受体。此外,我们还开发了将这些化合物转化为6-脱氧类似物的条件。终端甘露糖残基的6-位脱氧应防止这些化合物作为分枝杆菌中丰富的α-1,6-甘露糖基转移酶的底物,并应允许检测到负责将LM精细化为成熟的LAM以及高级PIMs生物合成的难以捉摸的α-1,2-甘露糖基转移酶活性。