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 TiCl(4). 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.