Here we report a glucosylation strategy mediated by ZnI2, a cheap and mild Lewis acid, for the highly stereoselective construction of 1,2-cis-O-glycosidic linkages using easily accessible and common 4,6-O-tethered glucosyl donors. The versatility and effectiveness of the α-glucosylation strategy were demonstrated successfully with various acceptors, including complex alcohols. This approach demonstrates the feasibility of the modular synthesis of various α-glucans with both linear and branched backbone structures.