{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)-3-{[2-(4-ethoxyphenyl)-2-oxoethyl]thio}-1-(4-fluorophenyl)-4-oxoazetidin-2-yl]phenoxy}acetic acid

(3R,4R)-1-(4-fluorophenyl)-3-[(3-nitropyridin-2-yl)dithio]-4-[4-(t-butoxycarbonylmethoxy)phenyl]azetidin-2-one

tert-butyl {4-[(2R,3R)-1-(4-fluorophenyl)-3-({2-[4-(methylthio)phenyl]-2-oxoethyl}thio)-4-oxoazetidin-2-yl]phenoxy}acetate