This invention relates to compounds of the formula ##STR1## and to pharmaceutically acceptable salts thereof. The compounds of formula 1 are potent antibacterial agents that may be used to treat various bacterial infections and disorders related to such infections. The invention also relates to pharmaceutical compositions containing the compounds of formula 1 and to methods of treating bacterial infections by administering the compounds of formula 1. The invention also relates to methods of preparing the compounds of formula 1 and to intermediates useful in such preparation.