teupernin A

(3S,3'aR,10'aR)-5β-(3-Furyl)-4,4',5,5',6',6'aβ-hexahydro-8'-methylspiro[furan-3(2H),7'(10'H)-naphtho[1,8a-c]furan]-2,3',10'(3'aβH)-trione