5,8a,11a,11b-Tetrahydroisoxazolo[5′,4′:3,4]pyrrolo[2,1-a] isoquinolin-8(6H)-ones were prepared by intramolecular cyclization of 5-(2-arylethyl)-6-hydroxytetrahydro-4H-pyrrolo[3,4-d]isoxazol-4-ones in the presence of boron trifluoride diethyl etherate.