The pharmaceutically acceptable salts of methyl (R)-7-[3-amino-4-(2 4 5-trifluoro-phenyl)-butyryl]-3-trifluoromethyl-5 6 7 8-tetrahydro-imidazo[1 5-a]pyrazine-1-carboxylate their preparation methods and their use for preparing antidiabetic medicaments are disclosed.