The invention relates to compounds of the formula I ##STR1## in which m denotes 1 or 2 and n denotes, 0, 1 or 2; R.sup.1 and R.sup.2 denote identical or different radicals from the series comprising hydrogen, optionally substituted alkyl, alkenyl, cycloalkyl, cycloalkenyl, cycloalkylalkyl, partly hydrogenated aryl and optionally substituted aralkyl; R.sup.3 and R.sup.4 denote identical or different radicals from the series comprising hydrogen, alkyl, alkenyl and optionally substituted aralkyl; Y denotes hydrogen or hydroxyl and Z denotes hydrogen, or Y and Z together denote oxo, and X denotes optionally substituted alkyl, alkenyl, cycloalkyl, optionally substituted 4-piperidinyl, optionally substituted aryl or indolyl, processes for their preparation, medicaments containing these compounds and their use, and to intermediates in their preparation.