(2R,3S)-3-Benzyl-2-[4-(4-methyl-piperazine-1-carbonyl)-phenoxy]-4-oxo-azetidine-1-carboxylic acid ((R)-1-phenyl-ethyl)-amide

(2S,3S)-3-Benzyl-2-[4-(4-methyl-piperazine-1-carbonyl)-phenoxy]-4-oxo-azetidine-1-carboxylic acid ((S)-1-phenyl-ethyl)-amide

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

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