Advances in Organoboron‐Catalyzed Regio‐ and Stereoselective Glycosylation

The efficient and stereoselective formation of glycosidic bonds remains a long‐standing challenge in carbohydrate chemistry, particularly in the synthesis of complex glycans, while conventional chemical methods often involve metal‐based catalysts and require harsh reaction conditions, which result in reduced chemo‐, stereo‐, and sometimes regiocontrol, particularly as chemical complexity in the substrates increases. In recent decades, organocatalysis has been a revolutionary approach, which offers sustainable and selective glycosylation strategies. Among the various organocatalysts explored, organoborons have demonstrated exceptional promise as mild and versatile activators of glycosylation reactions and for controlling the regioselectivity and stereoselectivity. This review highlights the recent advances in the use of boron‐based organocatalysts, specifically organoboranes and boronic acids, in glycosylation reactions. Herein, the focus is placed on their mechanistic roles as Lewis acids, their interactions with hydroxyl‐containing substrates, and their ability to modulate regioselectivity and stereoselectivity. Key contributions of boronic acids and organoboranes in promoting 1,2‐cis and 1,2‐trans glycosidic linkages, activating various classes of glycosyl donors, and enabling regio‐ and stereoselective transformations under mild conditions are critically examined. It is divided into two main sections: the first part focuses on the highly Lewis‐acidic borane B(C₆F₅)₃ catalyzed glycosylation, and the second part discusses RB(OH)₂‐based glycosylation and its potential for future research.