Most of the several cephalosporins that have been found to be clinically useful incorporate at the 7 position an acyl moiety derived from acetic acid, monosubstituted with an appropriate grouping such as thiophene, tetrazole. pyridylthio, or cyano. Structure-activity studies on cephalosporins teach that homologation or substitution of the acetic acid by a second grouping is generally undesirable from the standpoint of level and breadth of ...
