{(2R,3S)-3-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-2-[2-(4-nitro-benzyloxycarbonylamino)-ethylsulfanylthiocarbonylsulfanyl]-4-oxo-azetidin-1-yl}-(triphenyl-λ5-phosphanylidene)-acetic acid 4-nitro-benzyl ester

phosphoric acid 5-{(3S,4R)-3-[(R)-1-tert-butyldimethylsilyloxyethyl]-2-oxo-4-azetidinyl}pent-2-ynyl ester diethyl ester

2-{(2S,3S)-1-Benzyl-3-[(R)-1-(tert-butyl-dimethyl-silanyloxy)-ethyl]-4-oxo-azetidin-2-yl}-2-methyl-malonic acid diallyl ester

(1S,6S,8aS,8bR)-1-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-6-[2-(tert-butyl-dimethyl-silanyloxy)-ethyl]-2-oxo-1,2,5,6,7,8,8a,8b-octahydro-azeto[2,1-a]isoindole-4-carboxylic acid benzyl ester

((1R,4R)-4-{(2R,3S)-1-(tert-Butyl-dimethyl-silanyl)-3-[(R)-1-(tert-butyl-dimethyl-silanyloxy)-ethyl]-4-oxo-azetidin-2-yl}-3-oxo-cyclohexyl)-acetaldehyde