The boron-catalyzed approach provides good chemoselectivities based on the sizes of the silyl groups on the glycosyl acceptors, which enable one-pot iterative glycosylations. However, the same conditions were not translatable to donors that bear an N-acetyl moiety at the C2 position. Replacing N-acetyl functionality with azide (N3) and N-phthalimido (NPhth) promoted the reactivity at the cost of stereocontrol. 16a We envisioned that nitrogen protecting group modification might allow both reliable control of the stereochemical outcome and also facile conversion to the N-acetyl form at a late stage. In particular, we were attracted to work from Demchenko that illustrates utility of the Troc protecting group (CO2CH2CCl3) as a selection that embodies these features in other classes of chemoselective glycosylation. We started our investigations with the model study of N-Troc glucosamine fluoride 1 and 3-TMS (trimethylsilyl) protected acceptor 2 (Table ). Various catalyst loadings, concentrations, and catalysts were examined at room temperature (See Supporting Information). B(C6F5)3 and BF3•OEt2 performed very similarly with 10 mol % catalyst loading. However, an increased amount of isomerized a-fluoride 4 was obtained when the reaction system was extended to bis-silyl protected acceptor 5 with the use of BF3•OEt2 as the catalyst (Table ). Since our goal is to apply the chemistry towards the formation of complex oligosaccharides in a one-pot fashion, the ability to glycosylate with silyl protecting groups larger than TMS groups is crucial. Therefore, B(C6F5)3 was chosen as the optimal catalyst for further explorations given its excellent catalytic performance and simple experimental setup at room temperature without a requirement for molecular sieves. The feasibility of the reaction system was tested with both N-Troc-protected glucosamine fluoride and galactosamine fluoride (Scheme 2). This reaction system generated trans C1-C2 glycosidic linkages with C2, C3, C4, and C6 glycosyl acceptors in good yields (3, 6-9). The glycosidic linkage of GalNTroc(b 1-4)Glc in compound 8 can be transformed into GalNAc(b 1-4)Glc, which is part of the unique core structure for schistosome glycosphingolipids and Lewis X-hexasaccharide on the cercarial glycolipids. By differentiating the steric hinderance of the silyl protecting groups, the inherent reactivities of the hydroxyls on the acceptors can be inverted. As shown in the production of compound 10, the glycosylation first took place at the trimethylsilyl (TMS) protected secondary alcohol (C4 position), leaving dimethyl tert-butyl silyl (TBS) protected primary alcohol (C6 position) intact. Similarly, in the production of compound 6, the N-Troc glucosamine fluoride reacted with triethylsilyl (TES) protected C4 position instead of triisopropyl silyl (TIPS) protected C6 position to afford the product in 71% yield. Couplings with the larger triethylsilyl group while leaving a triisopropyl group at C6 unchanged, the yield of compound 6 was 78%. This feature enabled one-pot iterative glycosylations to synthesize amino sugars contained complex oligosaccharides. The method tolerates functional groups such as acid-sensitive acetal and alkene (7 and 11). Diosgenin, one of the most abundant aglycone part of saponins which are steroid or triterpenoid discovered in a variety of plants, has been proved to exhibit anti-inflammatory and antioxidant properties that could be applied towards various diseases. Towards this important structural class, the glycosylation between N-Troc-protected galactosamine fluoride and TMS-protected diosgenin proceeded in 92% yield, with similar performance when conducted on gram scale. The glycosylated product 11 is a precursor of a series of antimicrobial molecules, which had shown inhibitory effect towards several of the tested fungal strains and gram-positive bacteria species. Unfortunately, Nacetyl functionality is not compatible with this methodology even if when present in the glycosyl acceptor.