A method for preparing a parenterally administered anti-bacterial composition

The invention relates to a process for the preparation of parenterally administered pharmaceutical agents, said agents consisting of compounds of the formula (I) or salts thereof wherein R1 is hydrogen, methoxy or trifluoromethyl; R2 and R3, being the same or different from each other, are hydrogen or methyl; R4 is optionally substituted hydrocarbon residue and n denotes 0 or 1. The compounds show excellent antibacterial activities against the genus Campylobacter, especially against Campylobacter pylori, and they are used for preventing or treating infectious diseases caused by the said bacteria.