Developing efficient glycosylation methods and strategies is always a top priority and endless pursuit for carbohydrate chemists to acquire complex glycosidic linkages.While most glycosylation reactions are step-wise,that is,installation of the leaving group at the anomeric position first followed by activation and coupling with acceptors (Scheme 1a),dehydrative glycosylation is obviously more straightforward.[1] In this strategy,C1-hemiacetals are directly activated to couple with acceptors,thus obviating additional C1 modification steps (Scheme 1b).Unfortunately,the intrinsic stability of C1-hemiacetals impedes their applications.