Synthesis of a-o- and a-s-glycosphingolipids related to sphingomonous cell wall antigens using anomerisation

Abstract

Analogues of glycolipids from Spingomonadacaece with O- and S- and SO2-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 beta-thioglycuronic acids (beta-glycosyl thiols). The beta-O-glucuronide and beta-O-galacturonide precursors were efficiently prepared using benzoylated trichloroacetimidates. beta-Glycosyl thiols were precursors to beta-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.