Synonyms: 4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylicacid, 3,3-dimethyl-7-oxo-6-[(phenylacetyl)amino]- (2S,5R,6R)-, 4-oxide, (4R)-(9CI); 4-Thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid,3,3-dimethyl-7-oxo-6-[(phenylacetyl)amino]- (2S,5R,6R)-, 4-oxide, (4a)-; Benzylpenicillin R-sulfoxide