(2R,4R,5R,6S)-6-(1-Hydroxy-ethyl)-4-methyl-3,7-dioxo-1-aza-bicyclo[3.2.0]heptane-2-carboxylic acid 4-nitro-benzyl ester
(R)-2-{(2S,3S)-3-[1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-4-oxo-azetidin-2-yl}-thiopropionic acid S-phenyl ester
(R)-2-{(2S,3S)-3-[1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-4-oxo-azetidin-2-yl}-propionic acid
(4R,5R,6S)-3-(Diphenoxy-phosphoryloxy)-6-(1-hydroxy-ethyl)-4-methyl-7-oxo-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester
(S)-3-mercapto-1-(p-nitrobenzyloxycarbonyl)pyrrolidine