Synonyms: [2S-(2alpha,5alpha,6beta)]-3,3-dimethyl-7-oxo-6-(phenoxyacetamido)-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid 4-oxide;penicillin V sulfoxide;(2S,5S,6R)-3,3-Dimethyl-7-oxo-6α-[(phenoxyacetyl)amino]-4-thia-1-azabicyclo[3.2.0]heptane-2β-carboxylic acid-4-oxide;(2S,5R,6R)-3,3-dimethyl-4,7-dioxo-6-[[2-(phenoxy)acetyl]amino]-4$l^{4}-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid;(2S,5R,6R)-3,3-dimethyl-4,7-dioxo-6-[2-(phenoxy)ethanoylamino]-4$l^{4}-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid;(2S,5R,6R)-4,7-diketo-3,3-dimethyl-6-[[2-(phenoxy)acetyl]amino]-4$l^{4}-thia-1-azabicyclo[3.2.0]heptane-2-carboxylic acid