Acetic acid (6R,7S)-2-benzylcarbamoyl-7-methoxy-5,5,8-trioxo-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-en-3-ylmethyl ester

Acetic acid (6R,7S)-2-(benzyl-methyl-carbamoyl)-7-methoxy-5,5,8-trioxo-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-en-3-ylmethyl ester

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

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

t-butyl 3-acetoxymethyl-7α-methoxy-2-methylene-3-cephem-4-carboxylate 1β-oxide