| Abstract
| - Two major components of the cell wall in mycobacteria, including Mycobacterium tuberculosis,the causative agent of tuberculosis (TB), are polysaccharides containing arabinofuranose residues. In oneof these polysaccharides, arabinogalactan, this arabinan domain consists of three identical motifs of 22arabinofuranose residues, which are in turn attached to an underlying galactofuranan backbone. Recentstudies have proposed that this docosanasaccharide motif, and a structurally related arabinan present inanother cell wall polysaccharide, lipoarabinomannan, are biosynthesized from a common octadecasaccharide precursor. To facilitate the testing of this hypothesis, we report here the first total syntheses ofthese 18- and 22-residue oligosaccharides both functionalized with an aminooctyl linker arm. The route tothe target compounds involved the preparation of four tri- to heptasaccharide building blocks possessingonly benzoyl protecting groups that were coupled in a highly convergent manner via glycosyl trichloroacetimidate donors. Each of the targets could be prepared in only six steps from these intermediates, andin both cases more than 10 mg of material was obtained. These compounds are expected to be usefultools in probing the biosynthesis of these arabinan-containing polysaccharides. Such studies are essentialprerequisites for the identification of novel anti-TB agents that target arabinan assembly.
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