4(R)-<1-buten-3(R)-yl>-3(S)-<1(R)-<(tert-butyldimethylsilyl)oxy>ethyl>-2-oxoazetidine

(3S,4R)-3-[(R)-1-(tert-Butyl-dimethyl-silanyloxy)-ethyl]-4-(1-methyl-allyl)-azetidin-2-one

[(2R,3S)-2-((R)-3-Hydroxy-1-methyl-2-oxo-propyl)-4-oxo-3-((R)-1-triethylsilanyloxy-ethyl)-azetidin-1-yl]-(triphenyl-λ5-phosphanylidene)-acetic acid 4-methoxy-benzyl ester

[(2R,3S)-2-((R)-3-Acetoxy-1-methyl-2-oxo-propyl)-4-oxo-3-((R)-1-triethylsilanyloxy-ethyl)-azetidin-1-yl]-(triphenyl-λ5-phosphanylidene)-acetic acid 4-methoxy-benzyl ester

(3S,4R)-3-<(R)-1-tert-Butyldimethylsilyloxyethyl>-4-<(1R,2S)-2,3-epoxy-1-methylpropyl>-2-azetidinone