(3R,4R)-3-[(R)-1-(tert-butyldimethylsilyloxy)ethyl]-4-acetoxyazetidin-2-one
(3R,4R)-4-acetoxy-3-<(S)-1-(tert-butyldimethylsilyloxy)ethyl>-2-azetidinone
trans-4-acetoxy-3-[1-(tert-butyldimethylsilyloxy)ethyl]-2-azetidinone
4-Acetoxy-3-<1-(t-butyldimethylsiloxy)ethyl>-2-azetidinone
p-nitrobenzyl (6,1')erythro-5,6-trans-6-(1'-t-butyldimethylsilyloxyethyl)-2-oxo-penam-3-carboxylate