Strategies on the construction of 1,2-branched trans-β-glycosidic linkages and their applications in the synthesis of saponins

General strategies on the construction of 1,2-branched trans-β-glycosidic linkages and the corresponding logics are discussed herein. Linear strategies usually require a temporary acyl protecting group at C2-O position of the glycosylation donors to secure the requisite β-selective glycosylation. Convergent strategies involve selective formation of the trans-β-glycosidic linkages in the absence of neighboring participation, wherein solvent participation, invertive glycosylation, as well as other effects have to be exploited to achieve the β-selective glycosylation. These strategies are illustrated by representative applications in the synthesis of saponins.