We have developed a highly effective glycosylation method that involves the activation of 2-(2-propylsulfinyl)benzyl 1,2-orthoester glycosides using triflic anhydride (Tf 2 O). Our research indicates that half of the glycosyl donor is activated through Tf 2 O via an interrupted Pummerer reaction mechanism, while the remaining portion is activated by triflic acid (TfOH) generated in situ . As a result, as little as 0.5 equiv of Tf 2 O is adequate for activating the orthoester glycoside donors. This glycosylation procedure offers several benefits, such as high efficiency, wide applicability, and the utilization of a recyclable leaving group.