(3S,4aS,8aS,9aR)-3-(Trichloromethyl)octahydrooxazolo[3,4-a]indol-1(3H)-one is an intermediate in the synthesis of (2R,3aS,7aS)-Octahydroindole-2-carboxylic Acid Hydrochloride (O235975), an intermediate in the synthesis of Perindoprilat (P287530), an angiotensin-converting enzyme (ACE) inhibitor.