Novel cephalosporin derivatives possessing a bicyclic heterocycle at the 3-position. Part II: Synthesis and antibacterial activity of 3-(5-methylthiazolo[4,5-c]pyridinium-2-yl)-thiomethylcephalosporin derivatives and related compounds.

A series of cephalosporin derivatives with a thiazolopyridinium group at the 3-position was synthesized and evaluated for antibacterial activity. Some of these cephalosporin derivatives having a (5-alkylthiazolo[4,5-c]pyridinium-2-yl)thiomethyl group at the 3-position showed strong activity against Gram-positive and Gram-negative bacteria, including Pseudomonas aeruginosa. Among them, 5a showed a good antibacterial spectrum in vitro, and also showed a similar or slightly superior activity to that of ceftazidime in vivo against P. aeruginosa.