(5S,6R)-6-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-3-ethylcarbamoyloxymethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(6R,7R)-7-(1,3-Dioxo-1,3-dihydro-isoindol-2-yl)-3-ethylcarbamoyloxymethyl-8-oxo-4,5-dithia-1-aza-bicyclo[4.2.0]oct-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(R)-2-[(2R,3R)-2-(Benzothiazol-2-yldisulfanyl)-3-(1,3-dioxo-1,3-dihydro-isoindol-2-yl)-4-oxo-azetidin-1-yl]-3-ethylcarbamoyloxymethyl-but-3-enoic acid 4-nitro-benzyl ester