methyl 7β-chloroacetamido-2-methylene-3-methyl-3-cephem-4-carboxylate 1S(β)-oxide

benzhydryl 7α-bromo-3-methyl-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylate

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

(6R,7R)-7-Allyl-2-(2,2-dimethyl-propionyl)-7-methoxy-3-methyl-5,5-dioxo-5λ6-thia-1-aza-bicyclo[4.2.0]oct-2-en-8-one

(6R)-7t-benzoylamino-3-methyl-4c,7c-bis-methylsulfanyl-5ξ,8-dioxo-(6rH)-5λ4-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid methyl ester