(4-{(2R,3R)-1-(4-fluorophenyl)-3-[(3-nitropyridin-2-yl)dithio]-4-oxoazetidin-2-yl}phenoxy)acetic acid

{4-[(2R,3R)-1-(4-fluorophenyl)-3-({2-hydroxy-2-[4-(methylthio)phenyl]ethyl}thio)-4-oxoazetidin-2-yl]phenoxy}acetic acid

(4-{(2R,3R)-1-(4-fluoro-phenyl)-3-[(RS)-2-(4-fluoro-phenyl)-2-oxoethylsulfanyl]-4-oxo-azetidin-2-yl}-phenoxy)-acetic acid

[4-((2R,3R)-1-(4-fluorophenyl)-4-oxo-3-{[2-oxo-2-(4-pentylphenyl)ethyl]thio}azetidin-2-yl)phenoxy]acetic acid

N-{[4-((2R,3R)-1-(4-fluorophenyl)-3-{[2-(4-fluorophenyl)-2-hydroxyethyl]thio}-4-oxoazetidin-2-yl)phenoxy]acetyl}-D-alanine