[(2R,3S,5R)-5-(2-amino-6-oxo-1H-purin-9-yl)-2-[[[(2R,3S,5R)-2-[[[(2R,3S,5R)-5-(4-amino-2-oxopyrimidin-1-yl)-2-[[6-hydroxyhexoxy(oxo)phosphaniumyl]oxymethyl]oxolan-3-yl]oxy-oxophosphaniumyl]oxymethyl]-5-(6-aminopurin-9-yl)oxolan-3-yl]oxy-oxophosphaniumyl]oxymethyl]oxolan-3-yl]oxy-[[(2R,3S,5R)-3-[6-hydroxyhexoxy(oxo)phosphaniumyl]oxy-5-(5-methyl-2,4-dioxopyrimidin-1-yl)oxolan-2-yl]methoxy]-oxophosphanium