5-N-Acetyl-5-N,4-O-oxazolidinone protected alpha- and beta-sialyl phosphates react with allyltributylstannane and a variety of trimethylsilyl enol ethers to give alpha-sialyl C-glycosides in high yield and excellent selectivity. Elimination to give the 2,3-glycal is minimized by the presence of the oxazolidinone ring. The oxazolidinone ring can be subsequently cleaved under mild conditions at room temperature leaving in place the native acetamide group.