benzyl 6β-(2,2,2-trichloroethoxycarbonylamino)-6α-formamidopenicillanate 1β-oxide

6β-benzylideneamino-6α-methylsulfanyl-penicillanic acid benzyl ester

benzyl (2S,5R,6S)-6-amino-3,3-dimethyl-7-oxo-4-thia-1-azabicyclo[3.2.0]heptane-2-carboxylate