p-nitrobenzyl (5R,6S)-6-<(1R)-(tert-butyldimethylsiloxy)ethyl>-2-<((RS)-N-p-nitrobenzyloxycarbonylpiperidin-2-yl)methyl>-2-penem-3-carboxylate

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

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

p-nitrobenzyl 2-<(3S,4R)-3-<(1R)-(tert-butyldimethylsiloxy)ethyl>-4-<(RS-N-p-nitrobenzyloxycarbonylpiperidin-2-yl)carbonylthio>-2-oxoazetidin-1-yl>-2-hydroxyacetate

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