(2S-cis)-3,3-Dimethyl-7-oxo-4-thia-1-azabicyclo(3.2.0)heptane-2-carboxylic acid 4-Thia-1-azabicyclo(3.2.0)heptane-2-carboxylic acid, 3,3-dimethyl-7-oxo-, (2S-cis)- 87-53-6 EINECS 201-750-3 PENICILLANIC ACID