Synthesis of Neisseria meningitidis X capsular polysaccharide fragments

Serotype X of Neisseria meningitidis bacterium (Men X) recently emerged as a substantial threat to public health. Since anti-meningococcal vaccines currently available or under investigation do not contain antigenic components of Men X capsular polysaccharide, there is the need to develop more comprehensive conjugate vaccines capable to offer higher protection. As a preliminary step towards this goal, the synthesis of three conjugatable Men X capsular polysaccharide fragments is described. The installation of the crucial α-glycosyl phosphodiester linkages is based on the hydrogenphosphonate methodology using pure α-glycosyl hydrogenphosphonates 10 and 12 obtained from hemiacetals 9 and 11, respectively.