(3S,4R)-3-benzyl-4-(4-carboxy)phenoxy-1-[(R)-1-(phenylethyl)aminocarbonyl]azetidin-2-one

4-[(2S,3S)-3-Benzyl-4-oxo-1-((R)-1-phenyl-ethylcarbamoyl)-azetidin-2-yloxy]-benzoic acid

4-[(2S,3R)-3-Benzyl-4-oxo-1-((R)-1-phenyl-ethylcarbamoyl)-azetidin-2-yloxy]-benzoic acid

4-[(2S,3S)-3-Benzyl-3-ethyl-4-oxo-1-((R)-1-phenyl-ethylcarbamoyl)-azetidin-2-yloxy]-benzoic acid

4-[(2S,3S)-3-(2-Ethoxy-benzyl)-4-oxo-1-((R)-1-phenyl-propylcarbamoyl)-azetidin-2-yloxy]-benzoic acid