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

(2R,6R,7S)-7-Bromo-3-methyl-8-oxo-5-thia-1-aza-bicyclo[4.2.0]oct-3-ene-2-carboxylic acid tert-butyl ester

benzhydryl 7α-bromo-3-methyl-3-cephem-4-carboxylate-1,1-dioxide