Cephalosporins. III. 7-(O-Aminomethylphenylacetamido)cephalosporanic acids with bicyclic heteroaromatics in the C-3 side chain.

Bicyclic heteroaromatic thiols with a bridge-head nitrogen atom were used for nucleophilic substitution of 7-ACA at the C-3 acetoxy function followed by N-acylation of the 7-amino group with o-aminomethylphenylacetic acid to afford a series of new cephalosporins (24) with potent antibacterial activity against gram-positive and gram-negative organisms. The most active member of this series was 7-(o-aminomethylphenylacetamido)-3-(tetrazolo-[4,5-b]pyridazin-6-ylthiomethyl)-3-cephem-4-carboxylic acid (BB-S 226) (24e) with antibacterial activity superior activity superior to cephalothin and cefazolin.