Acetic acid (2R,3S,5R)-2-{4-[(2S,3R,5R)-2-formyl-5-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-tetrahydro-furan-3-yl]-3-oxo-butyl}-5-(5-methyl-2,4-dioxo-3,4-dihydro-2H-pyrimidin-1-yl)-tetrahydro-furan-3-yl ester

5'-{3-[(3'R)-5'-(4,4'-Dimethoxytrityl)-3'-deoxythymidin-3'-yl]-2-oxopropyl}-5'-deoxythymidine

2-Cyanoethyl {5'-[3-((3'R)-3'-deoxythymidin-3'-yl)-2-oxopropyl]-5'-deoxythymidin-3'-yl}(3'-acetylthymidin-5'-O-yl)phosphinate

5'-{3-[(3'R)-5'-(4,4'-Dimethoxytrityl)-3'-deoxythymidin-3'-yl]-2-oxopropyl}-3'-O-[2-cyanoethoxy(diisopropylamino)phosphino]-5'-deoxythymidine

1-[(2R,4R,5S)-5-(tert-Butyl-dimethyl-silanyloxymethyl)-4-(2-imidazol-1-yl-2-oxo-ethyl)-tetrahydro-furan-2-yl]-5-methyl-3-(2-trimethylsilanyl-ethoxymethyl)-1H-pyrimidine-2,4-dione