Abstract: The present invention provides compounds of the general formula (I) which inhibit the aggregation of erythrocytes or thrombocytes ##STR1## wherein A is hydrogen or C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.2 -C.sub.6 -alkynyl, benzyl or C.sub.3 -C.sub.7 -cycloalkyl radical, B is hydrogen, R.sub.1 is a C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl or C.sub.3 -C.sub.7 -cycloalkyl radical, R.sub.2 is a C.sub.1 -C.sub.6 -alkyl, C.sub.2 -C.sub.6 -alkenyl, C.sub.3 -C.sub.7 -cycloalkyl, C.sub.1 -C.sub.6 -alkylcarbonyl, C.sub.1 -C.sub.6 -alkoxycarbonyl, aminocarbonyl or hydrazinocarbonyl radical, or R.sub.1 and R.sub.2, together with the carbon atom to which they are attached, form a C.sub.3 -C.sub.7 -cycloalkyl ring, n is 0, X is a valency bond or a C.sub.1 -C.sub.6 -alkylene radical, R.sub.3 is a carbocyclic aromatic ring, which may be substituted; and the tautomers, optically-active forms and physiologically acceptable salts thereof with organic and inorganic acids.