3-[[(6R,7S)-7-methoxy-5,5,8-trioxo-2-(pyrrolidine-1-carbonyl)-5λ⁶-thia-1-azabicyclo[4.2.0]oct-2-en-3-yl]methylsulfanyl]-2-methyl-1H-1,2,4-triazine-5,6-dione

1,1-dimethylethyl 7α-methoxy-3-methyl-8-oxo-5-thia-1-azabicyclo<4.2.0>oct-2-ene-2-carboxylate

4-carboxybenzyl 3-(acetoxymethyl)-7α-methoxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene carboxylate 5,5-dioxide

(6R,7S)-3-Acetoxymethyl-7-methoxy-5,5,8-trioxo-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 3-methoxycarbonyl-benzyl ester

benzyl 3-(acetoxymethyl)-7α-methoxy-8-oxo-5-thia-1-azabicyclo<4.2.0>oct-2-ene-2-carboxylate