(5aR,5bR,7aS,8R,10aS,11aR,11bR,13aR)-8-(3-Furyl)-1,1,5a,7a,11b-pentamethyl-5b,6,7,7a,8,11b,13,13a-octahydrooxireno[4,4a]isochromeno[6,5-g][2]benzoxepine-3,10,12(1H,5aH,10aH)-trione