benzylpenicillinicacidpotassiumsalt cristapen eskacillin (2S,5R,6R)-3,3-Dimethyl-7-oxo-6-[(2-phenylacetyl)amino]-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid 2,2-Dimethyl-7beta-(phenylacetamido)cepham-3alpha-carboxylic acid (2S,5β)-3,3-Dimethyl-6α-(phenylacetylamino)-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2β-carboxylic acid potassium salt (2S,5β)-6α-(Benzylcarbonylamino)-7-oxo-3,3-dimethyl-1-aza-4-thiabicyclo[3.2.0]heptane-2β-carboxylic acid potassium salt (6R)-6-[(Phenylacetyl)amino]penicillanic acid potassium salt