Compound 18

rel-(5aR,8aR,8bS)-4,8b-dimethyl-1,7,8,8b-tetrahydro-8a,5a-(epoxyethano)cyclopenta[b]furo[3,4-d]pyran-3,10(6H)-dione

From: An eight-step gram-scale synthesis of (−)-jiadifenolide