The present invention relates to a process for the stereoselective preparation of compounds of formulae (1A) and (1B) and the salts thereof, particularly the physiologically acceptable salts thereof with inorganic or organic acids and bases, which have valuable pharmacological properties, particularly an inhibitory effect on signal transduction mediated by tyrosine kinases, the use thereof for the treatment of diseases, particularly tumoral diseases as well as benign prostatic hyperplasia (BPH), diseases of the lungs and airways.