A process for preparation of sodium salt of (2S, 5R)-sulfuric acid mono-(2-[1,3,4] oxadiazol-2- yl-7-oxo-1,6-diaza-bicyclo[3.2.1]oct-6-yl) ester is disclosed.Linvention concerne un procédé de préparation de sel de sodium du mono-(2-[1,3,4] oxadiazol-2-yl-7-oxo-1,6-diaza-bicyclo[3.2.1]oct-6-yl) ester de lacide (2S, 5R) sulfurique.