Challenges for stereoselective glycosylation of deoxy sugars are notorious in carbohydrate chemistry. We herein report a novel strategy for the construction of the less investigated beta-glycosidic bonds of 3,5-trans-3-amino-2,3,6-trideoxy sugars (3,5-trans-3-ADSs), which constitute the core structure of several biologically important antibiotics. Current protocol leverages a C-3 axial sulfonamide group in 3,5-trans-3-ADSs as a hydrogen-bond (H-bond) donor and repurposes substoichiometric phosphine oxide as an exogenous nucleophilic reagent (exNu) to establish an intramolecular H-bond between the former and the derived alpha-oxyphosphonium ion. This pivotal interaction stabilizes the alpha-face-covered intermediate to inhibit the formation of the more reactive beta-intermediate, thereby yielding reversed beta-selectivity, which is unconventional for an exNu-mediated glycosylation system. A wide range of substrates was accommodated, and good to excellent beta-selectivities were ensured by this H-bonding-assisted exNu effect. The robustness of the current strategy was further attested by the architectural modification of natural products and drugs containing 3,5-trans-3-ADSs, as well as the synthesis of a trisaccharide unit in avidinorubicin.