(3S,4S)-4-<<4-<(1,1-dimethylethoxy)carbonyl>phenyl>oxy>-3-ethyl-3-(phenylmethyl)azetidin-2-one

4-((2S,3S)-1-Benzylcarbamoyl-3-ethyl-3-isopropyl-4-oxo-azetidin-2-yloxy)-benzoic acid tert-butyl ester

4-((2S,3S)-1-Benzylcarbamoyl-3-ethyl-3-methoxymethyl-4-oxo-azetidin-2-yloxy)-benzoic acid tert-butyl ester

4-((2S,3S)-1-Benzylcarbamoyl-3-butyl-3-ethyl-4-oxo-azetidin-2-yloxy)-benzoic acid tert-butyl ester

4-[(2S,3S)-3-Ethyl-4-oxo-1-((R)-1-phenyl-ethylcarbamoyl)-3-propyl-azetidin-2-yloxy]-benzoic acid tert-butyl ester