Generalizing glycosylation: Synthesis of the blood group antigens Le(a), Le(b), and Le(X) using a standard set of reaction conditions

Because there are no general reaction conditions for any glycosylation method, biologically interesting oligosaccharides can only be made in a small number of laboratories in the world. To make carbohydrate synthesis accessible to nonspecialists, it is critical to have glycosylation methods that will work in a wide range of cases under a single set of conditions. The Lewis blood group antigens have attracted the attention of-numerous synthetic carbohydrate groups because of their structural complexity. Although they have been synthesized many times, they have never been made using a single glycosylation method under one set of reaction conditions. In this paper, we show that the sulfoxide glycosylation method can be used to form all of the glycosidic linkages in the Lewis blood group antigens Le(a) (1), Le(b) (2), and Le(x) (3) stereoselectively under a uniform set of reaction conditions. This work highlights the flexibility of the sulfoxide method and demonstrates its utility for constructing families of related oligosaccharides.