1-((2R,5S)-5-(((6-methoxy-2-oxido-4H-benzo[d][1,3,2]dioxaphosphinin-2-yl)oxy)methyl)-2,5-dihydrofuran-2-yl)-5-methylpyrimidine-2,4(1H,3H)-dione

5-fluoro-1-((2R,4S,5R)-4-hydroxy-5-(((6-methoxy-2-oxido-4H-benzo[d][1,3,2]dioxaphosphinin-2-yl)oxy)methyl)tetrahydrofuran-2-yl)pyrimidine-2,4(1H,3H)-dione