Oligonucleotides protected with N-(trimethylsilylethoxycarbonyl)(Teoc) and P- (trimethylsilylethanol)(Tse) groups were synthesized and deprotected by a single ZnBr2 treatment. Teoc group stabilized dA against depurination. This strategy was applied to the synthesis of base-sensitive oligonucleotide prodrugs bearing S-acetyl-2-thioethyl (Sate) phosphotriesters.