dl-p-nitrobenzyl 2-<(3R*,4S*)-3-<(1R*)-(tert-butyldimethylsiloxy)ethyl>-4-(5-p-nitrobenzyloxycarbonylaminopentanoylthio)-2-oxoazetidin-1-yl>-2-hydroxyacetate

(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<5-(p-nitrobenzyloxycarbonylamino)pentanoylthio>azetidin-2-one