7β-Acylamino-3-trifluoromethylsulfonyloxy-1-carba-3-cephem-4-carboxylic acid antibitic compounds, esters and salts thereof, and the corresponding 7-amino and protected 7-amino 1-carbacephalosporins are provided. The 3-trifluoromethylsulfonyloxy-substituted 1-carbacephalosporins also are useful in a process for preparing 3-halo-1-carbacephalosporins which comprises displacing the 3-trifluoromethylsulfonyloxy ester group with halide ion in an aprotic polar solvent.