EP2448950B1 - Synthesis of N4-(2,2-Dimethyl-4-[(dihydrogen Phosphonoxy)methyl]-3-Oxo-5-Pyrido[1,4]oxazin-6-Yl)-5-Fluoro-N2-(3,4,5-Trimethoxyphenyl)-2,4-Pyrimidinediamine Disodium Salt