Development and application of boronic-acid-catalyzed regioselective and 1,2-cis-stereoselective glycosylation

1,2-cis-Glycosides are frequently found in many biologically active natural products and pharmaceutical compounds. Therefore, to elucidate the precise biological roles of these carbohydrates and structure-activity relationships, the development of efficient glycosylation methods for the stereoselective synthesis of 1,2-cis-glycosides is becoming increasingly important in synthetic organic chemistry. In this review article, development of boronic-acid-catalyzed regioselective and 1,2-cis-stereoselective glycosylation that was recently developed in our laboratory, is introduced. This glycosylation method was successfully applied to the regioselective and stereoselective formation of 1,2-cis-β-glycosidic linkages, to the efficient synthesis of complex glycosides, and to the direct regioselective and 1,2-cis-stereoselective glycosylation of unprotected glycosides. Furthermore, mechanistic studies were consistent with a highly dissociative concerted S_Ni mechanism.