The invention relates to a new process for the preparation of compounds of the general Formula I ##STR1## wherein R stands for piperazinyl, 4-methyl-piperazinyl or 4-ethyl-piperazinyl group and pharmaceutically acceptable salts thereof which comprises reacting a compound of the general Formula II ##STR2## wherein R.sup.1 and R.sup.2 stand for halogen, for an aliphatic acyloxy group containing 2 to 6 carbon atoms and optionally substituted by halogen, or for an aromatic acyloxy group containing 7 to 11 carbon atoms with a piperazine derivative of the general Formula III ##STR3## wherein R.sup.3 stands for hydrogen, methyl or ethyl or a salt thereof and subjecting the compound of the general Formula IV ##STR4## thus obtained wherein R, R.sup.1 and R.sup.2 are as stated above to hydrolysis after or without isolation and if desired converting the compound of the general Formula I thus obtained into a salt thereof or setting free the same from its salt.The compounds of the general Formula I are known antibacterial agents.