S-(2R,3S)-3-[(1R)-1-(tert-butyldimethylsilanyloxy)ethyl]-1-(methylthio)-4-oxoazetidin-2-yl ethanethioate

S-(2R,3S)-3-((1R)-1-hydroxyethyl)-1-(methylthio)-4-oxoazetidin-2-yl ethanethioate

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

(5S,6S)-6-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-4-vinyl-1-aza-bicyclo[3.2.0]hept-3-en-7-one

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