tert-butyl (11S)-11-((tert-butyldimethylsilyl)oxy)-2-cyclopropyl-7-methoxy-5-oxo-8-((triisopropylsilyl)oxy)-11,11a-dihydro-1H-benzo[e]pyrrolo[1,2-a][1,4]diazepine-10(5H)-carboxylate