1 CEN 7beta-(4carboxybutanamido) cephalosporanic acid 1.000 2 CSC 4-(3-acetoxymethyl-2-carboxy-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-2-en-7-ylcarbamoyl)-1-carboxy-butyl-ammonium 0.800