Synthesis of Fluorinated Leishmania Cap Trisaccharides for Diagnostic Tool and Vaccine Development

Bearing in mind the often insufficient metabolic stability of carbohydrate antigens, which impairs both the bioavailability and immunogenicity of a given hapten, the development of chemically modified analogs with improved antigenicity is an important step towards effective glycoconjugate vaccines. Recently, strategic glycan fluorination has become an interesting approach to this, and several examples of fluorinated carbohydrate antigens that show better metabolic stabilities and comparable or even enhanced immunogenicities have been reported to date. In this paper, we present a small library of fluorinated trisaccharides based on a privileged motif from the lipophosphoglycan capping structure of Leishmania donovani, a protozoan parasite responsible for fatal visceral leishmaniasis. These epitope analogs were synthesized by a sequential [1+1+1] glycosylation strategy. An amine linker is present at the reducing end to allow conjugation and enable future applications in immunological studies for the development of diagnostic tools and vaccines. The preparation of fluorinated trisaccharides derived from the lipophosphoglycan capping structure of Leishmania donovani is reported. The essential β‐Gal‐(1→4)‐α‐Man motif is substituted with one or two fluorine atoms, and a functional linker is present at the reducing end. These new leishmanial antigen analogs are suitable for bioconjugation, and could be used for the development of new diagnostic tools and vaccines.