Structure--activity relationships in cephalosporins prepared from penicillins. 2. Analogues of cephalexin substituted in the 3-methyl group.

A previously outlined general procedure for preparing various 3-substituted cephalosporins from the penicillin nucleus has been used, with modifications where required, to prepare a series of analogues of cephalexin with various substituents in the 3-methyl group. The 3-substituents most conducive to broad-spectrum antibacterial activity were 3-pyridylmethyl and m- or p-carboxybenzyl. The compounds were only poorly absorbed by the oral route in mice, but the 3-(carboxybenzyl) compounds gave more prolonged useful serum levels than the usual cephalosporins.