| abstract |
New cephalosporin derivatives of the formula: ##STR1## in which R is an amino-protecting radical, R' is a protected carboxyl radical, Hal is a halogen atom, R a , R b and R c are hydrogen atoms, or R a is a protected carboxyl radical and R b and R c , which are identical or different, are hydrogen atoms, or C 1 -C 4 alkyl radicals, or together form a C 2 -C 5 alkylene radical, and n=0 or 1, their isomeric forms and mixtures thereof, are useful for the preparation of cephalosporins which have antibacterial properties. |