pivaloyloxymethyl (4R)-{(2R,3S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-oxoazetidin-2-y}-2-diaza-3-oxopentanoate

pivaloyloxymethyl (4R)-{(2R,3S)-3-[(1R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-oxoazetidin-2-y}-3-oxopentanoate

4-nitrobenzyl 2-((3S,4S)-3-((R)-1-((tert-butyldimethylsilyl)oxy)ethyl)-2-oxo-4-((R)-1-oxo-1-(((R)-5-oxopyrrolidin-3-yl)thio)propan-2-yl)azetidin-1-yl)-2-(triethoxy-l5-phosphaneylidene)acetate

4-nitrobenzyl 2-((3S,4S)-3-((R)-1-((tert-butyldimethylsilyl)oxy)ethyl)-2-oxo-4-((R)-1-oxo-1-(((R)-5-oxopyrrolidin-3-yl)thio)propan-2-yl)azetidin-1-yl)-2-(diethoxy(ethyl)-l5-phosphaneylidene)acetate

(R)-2-[(2S,3S)-3-((S)-1-Hydroxy-ethyl)-4-oxo-azetidin-2-yl]-propionic acid benzyl ester