[(2R,3S,4R,5R)-5-(6-aminopurin-9-yl)-4-hydroxy-2-[[hydroxy-[hydroxy-[(3R)-3-hydroxy-2,2-dimethyl-3-[2-[2-(2-methylpropanoylsulfanyl)ethylcarbamoyl]ethylcarbamoyl]propoxy]phosphoryl]oxy-phosphoryl]oxymethyl]oxolan-3-yl]oxyphosphonic acid