1-{(2R,4R,5S)-5-(tert-Butyl-dimethyl-silanyloxymethyl)-4-[2-oxo-3-(triphenyl-λ5-phosphanylidene)-propyl]-tetrahydro-furan-2-yl}-5-methyl-3-(2-trimethylsilanyl-ethoxymethyl)-1H-pyrimidine-2,4-dione

(E)-3'-O-Acetyl-5'-(3-{(3'R)-5'-O-(tert-butyldimethylsilyl)-3-[(2-trimethylsilylethoxy)methyl]-3'-deoxythymidin-3'-yl}-2-oxopropylidene)-5'-deoxythymidine