(R)-2-[(2S,3S)-4-Oxo-3-((R)-1-triethylsilanyloxy-ethyl)-azetidin-2-yl]-thiopropionic acid S-((R)-5-oxo-1-triethylsilanyl-pyrrolidin-3-yl) ester

(2-(diethoxy(ethyl)-l5-phosphaneylidene)-2-((3S,4S)-2-oxo-4-((R)-1-oxo-1-(((R)-5-oxo-1-(triethylsilyl)pyrrolidin-3-yl)thio)propan-2-yl)-3-((R)-1-((trimethylsilyl)oxy)ethyl)azetidin-1-yl)acetoxy)methyl pivalate

(3S,4S)-4-[(R)-1-[[(R)-2-oxo-1-(triethylsilyl)pyrrolidin-4-ylthio]carbonyl]ethyl]-1-[[(pivaloyloxy)methyloxy]oxalyl]-3-[(R)-1-(trimethylsilyloxy)ethyl]-2-azetidinone

(3S,4S)-3-[(R)-1-[[(R)-2-oxopyrrolidin-4-ylthio]carbonyl]ethyl]-3-[(R)-1-(triethylsilyloxy)ethyl]-2-azetidinone

(4R,5S,6S)-4-Methyl-7-oxo-3-((R)-5-oxo-1-triethylsilanyl-pyrrolidin-3-ylsulfanyl)-6-((R)-1-trimethylsilanyloxy-ethyl)-1-aza-bicyclo[3.2.0]hept-2-ene-2-carboxylic acid 2,2-dimethyl-propionyloxymethyl ester