Copyright © 2019 American Chemical Society. Regio- and stereoselective synthesis of 1,2-cis-glycosides has been achieved by catalytic anomeric O-alkylation using organoboron compounds. Modulating steric and electronic factors of both catalysts and substrates enables activation of the axially oriented anomeric oxygens of glucose-derived dialkoxyborates. The mild reaction conditions allow broad functional-group tolerance. This approach can be applied to the efficient sequential synthesis of oligosaccharides.