text: The development of facile chemical glycosylation protocols is essential to synthesizing complex oligosaccharides. Among many diverse type of glycosidic linkages, the 1,2-cis-β-glycoside, which exists in many biologically relevant glycoconjugates and oligosaccharides, is arguably one of the most difficult to synthesize. The challenges in constructing β-mannose linkage have been well documented in several reviews. To date, a few laboratories have devised efficient methodologies to overcome these synthetic hurdles, and achieved varying degrees of success. Of those elegant approaches, a highly stereoselective β-mannosylation protocol developed by Crich and co-workers was realized as a breakthrough in β-mannoside synthesis. This strategy is based on the initial activation of α-mannosyl sulfoxides 1 with triflic anhydride (TfO) using DTBMP (2,6-di-tert-butyl-4-methylpyridine) as a base, followed by nucleophilic substitution of glycosyl acceptors (HOR) to provide the 1,2-cis-β-glycoside 2 in good yield and selectivity (Scheme 1).