(6R,7R)-7-[3-(2-Methoxy-ethoxymethoxy)-tetrahydro-thiophen-3-yl]-2,2-dimethyl-3-oxa-1-aza-bicyclo[4.2.0]octan-8-one

(5S,6S)-3-(2-Acetylamino-ethylsulfanyl)-6-(3-hydroxy-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl)-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(5S,6S)-3-((E)-2-Acetylamino-vinylsulfanyl)-6-(3-hydroxy-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl)-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester

(6R,7R)-7-[3-(2-Methoxy-ethoxymethoxy)-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl]-2,2-dimethyl-3-oxa-1-aza-bicyclo[4.2.0]octan-8-one

{(2R,3R)-3-[3-(2-Methoxy-ethoxymethoxy)-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl]-4-oxo-azetidin-2-yl}-acetic acid

(2S,5S,6S)-6-(3-Hydroxy-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl)-3,7-dioxo-1-aza-bicyclo[3.2.0]heptane-2-carboxylic acid 4-nitro-benzyl ester

4-{(2R,3R)-3-[3-(2-Methoxy-ethoxymethoxy)-1,1-dioxo-tetrahydro-1λ6-thiophen-3-yl]-4-oxo-azetidin-2-yl}-3-oxo-butyric acid 4-nitro-benzyl ester