Synthesis and structure-activity relationships in the cefpirome series. II. Analogues of cefpirome with different 7-heteroarylacetamido and 3'-ammonium substituents.

The synthesis and antibacterial activity in vitro of 7-(2-heteroarylacetamido)-3-[(2,3- cyclopentenopyridinium)methyl]cephalosporins and of some related compounds with different ammonium functions in 3'-position are described. The 7-[5-amino-1,2,4-thiadiazol-3-yl] and the 7-[4-aminopyrimidin-2-yl] analogues of cefpirome and compounds with 3-aliphatic ammoniummethyl functions have excellent antibacterial activity. Cephalosporins with different N-heterocycles other than pyridine in 3'-position are less active than their 3-pyridiniummethyl analogues. Attachment of a pyridinium group to a cephem at C-3 via a thiomethyl or an aminomethyl bridge causes reduction of antibacterial activity.