[(3S,4S)-3-((S)-1-Hydroxy-2-methyl-propyl)-1-[(S)-1-(4-methoxy-phenyl)-ethyl]-2-oxo-4-(2-trimethylsilanyl-furan-3-yl)-azetidin-3-yl]-carbamic acid tert-butyl ester

(3S,4S,8S)-8-Isopropyl-2-[(S)-1-(4-methoxy-phenyl)-ethyl]-1,6-dioxo-3-(2-trimethylsilanyl-furan-3-yl)-7-oxa-2,5-diaza-spiro[3.4]octane-5-carboxylic acid tert-butyl ester