1-(4-fluorophenyl)-3-(R)-[(4-fluorobenzoyl)methylthio]-4-(R)-{4-[N-(α-(R)-{N-[2-(t-butoxy)-(1S)-(t-butoxycarbonyl)ethyl]carbamoyl}benzyl)carbamoylmethoxy]phenyl}azetidin-2-one

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

{4-[(2R,3R)-3-{[2-(1,3-benzodioxol-5-yl)-2-hydroxyethyl]thio}-1-(4-fluorophenyl)-4-oxoazetidin-2-yl]phenoxy}acetic acid

{4-[(2R,3R)-3-[(RS)-2-(2,3-dihydro-benzo[1,4]dioxin-6-yl)-2-hydroxy-ethylsulfanyl]-1-(4-fluoro-phenyl)-4-oxo-azetidin-2-yl]-phenoxy}-acetic acid