benzhydryl 3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

(R)-3-(1-Methyl-1H-tetrazol-5-ylsulfanylmethyl)-5,5,8-trioxo-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid tert-butyl ester

sodium 3-methyl-5,5,8-trioxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

tert-butyl 3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-3-ene-2-carboxylate

tert-butyl 3-(bromomethyl)-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-3-ene-2-carboxylate