p-Nitrobenzyl 7-(phenoxyacetamido)-3-methylenecepham-4-carboxylate
(6R)-3-methylene-8-oxo-7t-(2-phenoxy-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid 4-nitro-benzyl ester
(6R,7R)-3-Hydroxy-8-oxo-7-(2-phenoxy-acetylamino)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 4-nitro-benzyl ester