1,2,5-ortho esters of D-arabinose as versatile arabinofuranosidic building blocks. Concise synthesis of the tetrasaccharidic cap of the lipoarabinomannan of Mycobacterium tuberculosis

1,2,5-ortho esters of d-arabinose were found to be ideally suited building blocks for the stereoselective formation of alpha and beta arabinofuranosidic linkages after nucleophilic opening of the orthoester with oxygen and sulfur nucleophiles; the tetrasaccharidic cap of the lipoarabinomannan of Mycobacterium tuberculosis was then synthesized in a highly convergent manner.