(R)-4-ethyldihydrofuran-2(3H)-one

γ-丁内酯

4-cyanomethyl-3,4-dihydro-2(5H)-furanone

(3aR,3bR,6aS,6bS)-Tetrahydro-2,5-dioxa-cyclobutadicyclopentene-1,4-dione

(3aR,3bR,6aR,6bR)-tetrahydrocyclobuta[1,2-c:3,4-c']difuran-1,6(6aH,6bH)-dione