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

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

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

t-butyl 7α-methoxy-3-methyl-3-cephem-4-carboxylate 1,1-dioxide

(4S,5S,6R,7S)-3-Acetoxymethyl-7-methoxy-4-methyl-5,8-dioxo-5λ4-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid tert-butyl ester