Process for stabilizing acid 2- {n - {(s) -1-etoxycarbonyl-3-phenylpropyl} -l-alanyl} - (1s, 3s, 5s) -2-azabicyclo- {3.3,0} -octane- 3-carboxylic acid (ramipril) and of stabilized pharmaceutical compositions that contain it

Stabilised compounds of the formula I … … in which R, R , R , R , R and R have the stated meanings, and process for the preparation thereof are described. The stabilised compounds are suitable for the production of pharmaceutical preparations.