5'-O-(4,4'-dimethoxytrityl)-N6-benzoyl-deoxyadenosine-3'-O-(2-selena-spiro-4,4-pentamethylene-1,3,2-oxathiaphospholane)

5'-O-(4,4'-dimethoxytrityl)-N2-isobutyryl-deoxyguanosine-3'-O-(2-selena-spiro-4,4-pentamethylene-1,3,2-oxathiaphospholane)