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 compds. 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. Immunol. evaluation of the three sulfated compds. 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.