A Concise Synthesis of l -Altruronic Acid: A Rare Sugar Located in the Surface Antigen of Enterococcus faecium

l-Altruronic acid-based glycoconjugates demonstrate excellent preliminary efficacy as antigens for Enterococcus faecium vaccine development; however, progress has been limited by the poor accessibility of l-altruronic acid. We report here on a concise preparation of a donor-functionalized derivative of l-altruronic acid via a fluorine-directed C-5 epimerization. DFT calculations also reveal how the stereoselectivity of epimerization is influenced by stabilizing effects in the intermediate carbohydrate radicals.