P-({[(hydroxy{[(2S,3S,4R,5R)-5-(2,4-dioxo-3H-pyrimidin-1-yl)-3,4-dihydroxytetrahydro-2-furyl]methyl}(oxo)-λ5-phosphanyl)oxy](hydroxy)(oxo)-λ5-phosphanyl}oxy)-P-({[(2R,3S,4R,5R)-5-(2,4-dioxo-3H-pyrimidin-1-yl)-3,4-dihydroxytetrahydro-2-furyl]methyl}oxy)phosphinate sodium salt