3-[[(1R,3R,4R,7S)-1-[[Bis(4-methoxyphenyl)-phenylmethoxy]methyl]-3-(5-methyl-2,4-dioxopyrimidin-1-yl)-2,5-dioxabicyclo[2.2.1]heptan-7-yl]oxy-[di(propan-2-yl)amino]phosphanyl]oxypropanenitrile