We describe efficientsialylationreactions in CH2Cl2 with the use of silylene/oxazolidinonedouble-lockedsialicacidbuildingblocks. The buildingblocks were synthesized from 4,5-oxazolidinone-protected phenylthiosialoside. In sialylationreactions towards primary and relatively reactive secondary hydroxy groups on the galactosides, the double-lockedbuildingblocks provided desired coupling products