(3S,4S)-4-(diphenylmethoxycarbonyl)phenoxy-1-[(diphenylmethyl)aminocarbonyl]-3-(2-ethoxybenzyl)azetidin-2-one

(3S,4S)-4-(4-diphenylmethoxycarbonyl)phenoxy-3-(2-methoxybenzyl)-1-[(R)-(1-phenylpropyl)aminocarbonyl]azetidin-2-one

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

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

(3S,4S)-4-[4-(1,1-diphenylmethoxycarbonyl)phenoxy]-3-(2-ethoxybenzyl)azetidin-2-one