(3R)-4-((1bS,3S)-1b-(4-fluorophenyl)-7-hydroxy-7-isopropyl-1a-phenyl-7a-(phenylcarbamoyl)hexahydro-1aH-oxireno[2′,3′:3,4]pyrrolo[2,1-b][1,3]oxazin-3-yl)-3-hydroxybutanoic acid