(3S,4S)-1-(p-nitrobenzyloxycarbonylmethyl)-4-[(1R)-1-phenylthiocarbonylethyl]-3-[(1R)-1-trimethylsilyloxyethyl]-2-azetidinone

(4R,5R,6S,8R)-p-nitrobenzyl-3-(diphenylphosphoryloxy)-4-methyl-6-(1-(trimethylsilyloxy)ethyl)-7-oxo-1-azabicyclo(3.2.0)hept-2-ene-2-carboxylate

(3S,4S)-3-[(1R)-1-hydroxyethyl]-4-[(1R)-1-phenylthiocarbonylethyl]-1-carboxymethylazetidin-2-one

(3S,4S)-1-(tert-butoxycarbonylmethyl)-3-[(1R)-1-tert-butyldimethylsilyloxyethyl]-4-[(1R)-1-phenylthiocarbonylethyl]-2-azetidinone

(3S,4S)-3-<(1R)-1-hydroxyethyl>-1-(p-nitrobenzyloxycarbonylmethyl)-4-<(1R)-1-phenylthiocarbonylethyl>-2-azetidinone