Antibacterial cephalosporins of the following formula: ##STR1## WHEREIN A and B each is a hydrogen or an amino protecting group; X is a hydroxy or a carboxy protecting group; Y is a hydrogen, halogen, alkyl, alkoxy, or an alkylthio; R is a hydrogen or an alkyl; Z is a group of the formula ##STR2## (in which R.sup.1 and R.sup.2 are the same or different and are a hydrogen, optionally substituted hydrocarbon group, organic acyl, or a group of the formula ##STR3## respectively, in which M and M' are the same or different and are an oxygen or sulfur; R.sup.3 is a hydrocarbon group; R.sup.1 and R.sup.2 can be combined together directly or through a hetero atom); m is 0 or 1; and the broken line shows the presence of a double bond at position 2 or 3, preparable from the compounds shown by the above formula in which Z is an oxygen by treatment with a compound shown by the formula H.sub.2 Z; and pharmaceuticals containing these compounds.