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

(3S,4R)-1-(tert-Butyl-dimethyl-silanyl)-3-[(R)-1-(tert-butyl-dimethyl-silanyloxy)-ethyl]-4-{(1R,4R)-4-[(E)-3-(1,3-dimethyl-2-oxo-2λ5-[1,3,2]diazaphospholidin-2-yl)-allyl]-2-oxo-cyclohexyl}-azetidin-2-one

(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

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

1-{(2S,3S)-3-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-4-oxo-azetidin-2-yl}-2-oxo-cyclohex-3-enecarboxylic acid allyl ester