Biological activity of new aza analogues of quinolones

A series of novel derivatives of 4H-pyrido1,2-a]pyrimidine, 1,4-dihydro-4-oxo-1,5-naphthyridine and 1,4-dihydro-4-oxo-1,6-naphthyridine were prepared and their biological activity was compared with that of nalidixic acid. Thein vitro antibacterial activity of the tested compounds was lower than that of nalidixic acid except for two agents,1b and2c, with a higher activity againstEnterococcus faecalis. The compounds were tested for their ability to cure four plasmids from two species ofEnterobacteriaceae. The derivatives eliminated three plasmids (pKM101, pBR322, F'lac) at one-half or one-quarter of the minimal inhibitory concentration. Plasmid RP4 was unaffected by the treatment. None of these compounds showed better antichloroplast activity than nalidixic acid.