(1R,6R,8R,9S)-6-((bis(4-methoxyphenyl)(phenyl)methoxy)methyl)-8-(5-methyl-2,4-dioxo-3,4-dihydropyrimidin-1(2H)-yl)-2,5,7-trioxabicyclo[4.2.1]nonan-9-yl (2-cyanoethyl) diisopropylphosphoramidite