A new strategy for the protection of deoxyguanosine during oligonucleotide synthesis

The protection of the 6-oxo group of deoxyguanosine with the 2-trimethylsilylethyl ($\text{2}$), phenylthioethyl ($\text{3}$), 4-nitrophenylthioethyl ($\text{4}$), 4-nintrophenethyl ($\text{5}$), and cyanoethyl ($\text{6}$) groups is described. Each protecting group is introduced in good yield and is cleaved under mild conditions. Compatibility with the various approaches to oligonucleotide synthesis is discussed.