Modified amino acids, pharmaceuticals containing these compounds and method for their production

234 11 The present invention relates to modified amino acids of general formula wherein A, Z, X, n, m, R, R, R, Rand Rare defined as in claims to , their tautomers, their diastereomers, their enantiomers, the mixtures thereof and the salts thereof, particularly the physiologically acceptable salts thereof with inorganic or organic acids or bases, pharmaceutical compositions containing these compounds, the use thereof and processes for preparing them as well as their use for the production and purification of antibodies and as labelled compounds in RIA- and ELISA assays and as diagnostic or analytical aids in neurotransmitter research.