p-nitrobenzyl 2-<(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<((2S)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl)acetylthio>-2-oxoazetidin-1-yl>-2-triphenylphosphoranylideneacetate

(S)-2-Carboxymethyl-pyrrolidine-1-carboxylic acid 4-nitro-benzyl ester

<(2S)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl>thioacetic S-acid

(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<(2S)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl>carbonylthioazetidin-2-one

(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<<(2S)-N-p-nitrobenzyloxycarbonylpyrrolidin-2-yl>acetylthio>azetidin-2-one