N-[9-[(1r,3s,4s,6r,7s)-4-[[bis(4-methoxyphenyl)-phenylmethoxy]methyl]-7-[2-cyanoethoxy-[di(propan-2-yl)amino]phosphanyl]oxy-3-methyl-2,5-dioxabicyclo[2.2.1]heptan-6-yl]purin-6-yl]benzamide