6-Hydroxy-5-[2-(naphthalen-1-yl)ethyl]-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,4-d]isoxazol-4-ones in the presence of boron trifluoride-diethyl ether complex underwent cyclization to benzo[f]isoxazolo[5',4': 3,4]- pyrrolo[2,1-a]isoquinoline derivatives as mixtures of two diastereoisomers. Analogous cyclization of 6-hydroxy-5-(naphthalen-1-ylmethyl)-3a,5,6,6a-tetrahydro-4H-pyrrolo[3,4-d]isoxazol-4-ones gave benzo[de]isoxazolo[ 5',4': 3,4]pyrrolo[2,1-a]isoquinolines as a single diastereoisomer. The cyclization of 6-hydroxy-5-[2-(1Hindol-3-yl)ethyl]-6,6a-dihydro-3aH-pyrrolo[3,4-d]isoxazol-4(5H)-ones catalyzed by Sn(NTf₂)₄ afforded isoxazolo[ 5',4': 1,2]indolizino[8,7-b]indol-4(12H)-ones in moderate yields. 6-Hydroxy-5-[2-(thiophen-2-yl)ethyl]- 6,6a-dihydro-3aH-pyrrolo[3,4-d]isoxazol-4(5H)-ones were converted to 4,5,10a,10b-tetrahydroisoxazolo- [5,4-a]thieno[2,3-g]indolizin-7(7aH)-one derivatives in the presence of BF₃ · Et₂O or Sn(NTf₂)₄.