A process for the preparation of compound of the formula ##STR1## in which R.sup.1 --represents ##STR2## and R.sup.2 --represents hydrogen, fluorine, chlorine or bromine. Comprising cyclizing compounds of the formula ##STR3## and, in a further step, either a) reducing stereo-specifically to give compounds of the formula in which R.sup.1 represents ##STR4## or b), to give compounds of the formula in which R.sup.1 represents ##STR5## or by c) forming compounds of the formula ##STR6## followed by stereoselective reduction to give compounds in which R.sup.1 represents ##STR7##