6-Amidinopenicillanic acid derivatives wherein one of the nitrogen atoms of the amidino group is part of a heterocyclic ring having on a side chain an unsubstituted heterocyclic ring containing 2 to 3 nitrogen atoms, and being useful as an antibiotic.
The invention provides novel compounds having the general formula:
wherein A, R1, R2 and R3 are as defined herein, compositions including the compounds and methods of using the compounds.