(2R,3S,5R)-2-((bis(4-methoxyphenyl)(phenyl)methoxy)methyl)-5-(2-oxo-9-(2-(2,2,2-trifluoroacetamido)ethoxy)-2,10-dihydro-3H-benzo[b]pyrimido[4,5-e][1,4]oxazin-3-yl)tetrahydrofuran-3-yl (2-cyanoethyl) diisopropylphosphoramidite