报道了第一个立体选择性全合成 β-d-甘露糖基磷酸酯。为了在链中引入立体中心,使用两种不同的不对称催化共轭添加方案制备了三个线性手性构件。使用 Julia-Kocienski 序列影响各种线性片段的偶联。这种方法构成了构建任何长度和立体化学的饱和低聚异戊二烯链的通用和收敛方法。此外,形成困难的 β-甘露糖基磷酸酯键的另一种方法已被证明是成功的。全 S 化合物的生物学评估表明,其对 T 细胞的抗原效力与天然产物相同。
Highly Stereocontrolled Total Synthesis of β-d-Mannosyl Phosphomycoketide: A Natural Product from Mycobacterium tuberculosis
摘要:
beta-D-Mannosyl phosphomycoketide (C-32-MPM), a naturally occurring glycolipid found in the cell walls of Mycobacterium tuberculosis, acts as a potent antigen to activate T-cells upon presentation by CD1c protein. The lipid portion of C-32-MPM contains, a C-32-mycoketide, consisting of a saturated oligoisoprenoid chain with five chiral methyl branches. Here we develop several stereocontrolled approaches to assemble the oligoisoprenoid chain with high stereopurity (>96%) using Julia-Kocienski olefinations followed by diimide reduction. By careful choice of olefination sites, we could derive all chirality from a single commercial compound, methyl (2S)-3-hydroxy-2-methylpropionate (>99% ee). Our approach is the first highly stereocontrolled method to prepare C-32-MPM molecule with >96% stereopurity from a single >99% ee starting material. We anticipate that our methods will facilitate the highly stereocontrolled synthesis of a variety of other natural products containing chiral oligoisoprenoid-like chains, including vitamins, phytol, insect pheromones, and archaeal lipids.