(6R)-7t-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-3,8-dioxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid benzhydryl ester
cefroxadine
(6R)-3-benzyloxy-7t-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-8-oxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester
(6R)-7t-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-3-ethoxy-8-oxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid benzhydryl ester
(6R)-7t-((R)-2-tert-butoxycarbonylamino-2-phenyl-acetylamino)-2-methyl-3,8-dioxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid benzhydryl ester