Synthesis of Sulfated Galactocerebrosides from an Orthogonal b-d- Galactosylceramide Scaffold for the Study of CD1-Antigen Interactions

CD1a protein binds sulfatide (3-O-sulfo-b-d-galactosylceramide) to form an antigen complex that interacts with T cell receptors and activates T cells. To assess the role of the position of the sulfate in T cell activation, the synthesis of three b-d-galactosylceramides, variously bearing a sulfate at position 2, 4, or 6 of galactose, has been planned and carried out. The compounds were synthesized by an orthogonal sulfation strategy from a common b-d-galactosylceramide scaffold, which was in turn obtained through an efficient glycosylation reaction between a fully orthogonally protected galactosyl imidate and 3-O- benzoylazidosphingosine. Immunological evaluation of the three sulfated compounds in CD1a-mediated T cell activation, in comparison with natural sulfatide, provided evidence of the influence of the sulfate position in the recognition event between the antigen, the CD1 protein and the T cell receptor.