5,5,7a,7b,12,12,15b-heptamethyl-5,5a,6,7,7a,7b,8,9,10,11,12,13,13a,13b,14,15,15a,15b-octadecahydro-3H-13,9a-(epoxymethano)chryseno[2,1-c]oxepin-3-one