(3R,4R)-4-benzoyloxy-3-<(1R)-(1-tert-butyldimethylsiloxy)ethyl>-azetidin-2-one
(3R,4R)-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-acetoxyazetidin-2-one
(2R,6S,7S)-4-(benzyloxy)-7-((R)-1-((tert-butyldimethylsilyl)oxy)ethyl)-5,8-dioxo-1,4-diazabicyclo[4.2.0]octane-2-carboxylic acid
3(S)-<1(R)-<(tert-butyldimethylsilyl)oxy>ethyl>-4(R)-<<<<2-<<(p-nitrobenzyloxy)carbonyl>amino>ethyl>thio>carbonyl>methyl>azetidin-2-one
3(S)-<1(R)-<(tert-butyldimethylsilyl)oxy>ethyl>-4(R)-<<(phenylthio)carbonyl>methyl>azetidin-2-one