(6R)-3,7c-dimethyl-8-oxo-7t-(2-phenoxy-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid
(6R)-3,7c-dimethyl-8-oxo-7t-(2-phenyl-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid tert-butyl ester
(6R)-7c-acetyl-3-methyl-8-oxo-7t-(2-phenyl-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid tert-butyl ester
(6R)-7c-acetyl-3-methyl-8-oxo-7t-(2-phenoxy-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid tert-butyl ester
(6R)-3,7c-dimethyl-8-oxo-7t-(2-phenyl-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid