Disclosed are 6- and 6,6-disubstituted-3-substituted amino-1-azabicyclo[3.2.0]hept-2-en-7-one-2-carboxylic acids (I): ##STR1## wherein R.sup.1 and R.sup.2 are, inter alia, independently selected from the group consisting of hydrogen, substituted and unsubstituted: alkyl, aryl, and aralkyl; and R' and R" are independently selected from the group consisting of: H, substituted and unsubstituted alkyl and aralkyl, or together form a substituted or unsubstituted cyclic group.Such compounds and their pharmaceutically acceptable salt, ester and amide derivatives are useful as antibiotics. Also disclosed are processes for the preparation of such compounds, pharmaceutical compositions comprising such compounds and methods of treatment comprising administering compounds and compositions when an antibiotic effect is indicated.