EP2477967A1 - PROCESS FOR PREPARING 3-[(4S)-8-BROMO-1-METHYL-6-(2-PYRIDINYL)-4H-IMIDAZOL[1,2-A][1,4]BENZODIAZEPINE-4-YL]PROPIONIC ACID METHYL ESTER OR THE BENZENE SULFONATE SALT THEREOF, AND COMPOUNDS USEFUL IN THAT PROCESS