The invention relates to compounds of the formula I ##STR1## in which n denotes 0 or 1,R denotes hydrogen, alkyl or aralkyl, R.sup.1 denotes hydrogen or alkyl, which can optionally be substituted by amino, acylamino or benzoylamino, alkenyl, cycloalkyl, cycloalkenyl, cycloalkylalkyl, aryl or partially hydrogenated aryl, which each can be substituted by alkyl, alkoxy or halogen, arylalkyl or aroylalkyl, both of which can be substituted in the aryl radical as defined in the aforegoing, a monocyclic or bicyclic sulfur or oxygen and/or nitrogen heterocyclic radical, or a side chain of a naturally occurring aminoacid, R.sup.2 denotes hydrogen, alkyl, alkenyl or arylalkyl, Y denotes hydrogen or hydroxyl, Z denotes hydrogen or Y and Z together denote oxygen and X denotes alkyl, alkenyl, cycloalkyl, aryl, which is monosubstituted, disubstituted or trisubstituted by alkyl, alkoxy, hydroxyl, halogen, nitro, amino, alkylamino, dialkylamino or methylenedioxy or 3-indolyl,and their physiologically acceptable salts, processes for their preparation, agents containing these and their use as medicaments and also bicyclic amino acids as their intermediates and processes for their preparation.