Synthesis of α-O- and α-S-glycosphingolipids related to sphingomonous cell wall antigens using anomerisation

Analogues of glycolipids from Spingomonadacaece with O- and S- and SO ₂-linkages have been prepared using chelation induced anomerisation promoted by TiCl₄. Included are examples of the anomerisation of intermediates with O- and S-glycosidic linkages as well as isomerisation of β-thioglycuronic acids (β-glycosyl thiols). The β-O-glucuronide and β-O-galacturonide precursors were efficiently prepared using benzoylated trichloroacetimidates. β-Glycosyl thiols were precursors to β-S-derivatives. Triazole containing mimics of the natural glycolipids were prepared using CuI promoted azide-alkyne cycloaddition reactions in THF. The glycolipid antigens are being evaluated currently for their effects on iNKT cells.