Wang Lizhen, Feng Shaojie, An Lian, Gu Guofeng, Guo Zhongwu
National Glycoengineering Research Center, School of Life Science, Shandong University , Jinan 250100, China.
J Org Chem. 2015 Oct 16;80(20):10060-75. doi: 10.1021/acs.joc.5b01686. Epub 2015 Sep 29.
Lipoarabinomannan (LAM) is one of the major constituents of the Mycobacterium tuberculosis cell wall and an attractive molecular scaffold for antituberculosis drug and vaccine development. In this paper, a convergent strategy was developed for the synthesis of LAM oligosaccharides with an α-1,2-linked dimannopyranose cap at the nonreducing end. The strategy was highlighted by efficient coupling of separately prepared nonreducing end and reducing end oligosaccharides. Glycosylations were mainly achieved with thioglycoside donors, which gave excellent yields and stereoselectivity even for reactions between complex oligosaccharides. The strategy was utilized to successfully synthesize tetra-, hepta-, and undecasaccharides of LAM from d-arabinose in 10, 15, and 14 longest linear steps and 7.84, 7.50, and 2.59% overall yields, respectively. The resultant oligosaccharides with a free amino group at their reducing end were effectively conjugated with carrier proteins, including bovine serum albumin and keyhole limpet hemocyanin (KLH), via a bifunctional linker. Preliminary immunological studies on the KLH conjugates revealed that they could elicit robust antibody responses in mice and that the antigen structure had some influence on their immunological property, thus verifying the potential of the oligosaccharides for vaccine development and other immunological studies.
脂阿拉伯甘露聚糖（LAM）是结核分枝杆菌细胞壁的主要成分之一，是抗结核药物和疫苗开发中具有吸引力的分子支架。本文开发了一种收敛策略，用于合成在非还原端带有α-1,2-连接的二甘露吡喃糖帽的LAM寡糖。该策略的突出之处在于分别制备的非还原端和还原端寡糖的有效偶联。糖基化主要通过硫代糖苷供体实现，即使对于复杂寡糖之间的反应，也能获得优异的产率和立体选择性。该策略被用于从d-阿拉伯糖成功合成LAM的四糖、七糖和十一糖，最长线性步骤分别为10步、15步和14步，总产率分别为7.84%、7.50%和2.59%。所得还原端带有游离氨基的寡糖通过双功能连接子与载体蛋白（包括牛血清白蛋白和钥孔血蓝蛋白（KLH））有效偶联。对KLH偶联物的初步免疫学研究表明，它们可以在小鼠体内引发强烈的抗体反应，并且抗原结构对其免疫学性质有一定影响，从而验证了寡糖在疫苗开发和其他免疫学研究中的潜力。
