(6R)-3-chloro-8-oxo-7t-(2-thiophen-2-yl-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 4-nitro-benzyl ester
2-thienylacetic acid chloride
(6R)-7t-amino-3-methylene-8-oxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid 4-nitro-benzyl ester
(6R)-3,8-dioxo-7t-(2-thiophen-2-yl-acetylamino)-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid 4-nitro-benzyl ester
(6R)-7t-amino-3,8-dioxo-(6rH)-5-thia-1-aza-bicyclo[4.2.0]octane-2ξ-carboxylic acid 4-nitro-benzyl ester; hydrochloride