[(2R,3S)-2-[(R)-5-tert-Butoxycarbonylamino-1-(2-hydroxy-acetyl)-pentyl]-4-oxo-3-((R)-1-triethylsilanyloxy-ethyl)-azetidin-1-yl]-(triphenyl-λ5-phosphanylidene)-acetic acid benzhydryl ester

(3S,4R)-3-<(1R)-1-triethylsilyloxyethyl>-4-<(1R)-1-(4-azidobutyl)-2-oxo-3-acetoxypropyl>-2-azetidinone