[2-((E)-3-Methoxyamino-acryloylsulfanyl)-4-oxo-azetidin-1-yl]-(triphenyl-λ5-phosphanylidene)-acetic acid 4-nitro-benzyl ester

Chloro-(2-oxo-4-tritylsulfanyl-azetidin-1-yl)-acetic acid 4-nitro-benzyl ester

Sodium; 3-((E)-2-methoxyamino-vinyl)-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylate

3-Methylsulfanylmethyl-7-oxo-4-thia-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 4-nitro-benzyl ester