(3aβ,,6aα,9aα,9bβ,9cβ)-1,2,3,3a,6a,9a,9b,9c-Octahydro-1,1,6,8,8,9c-hexamethyl-5H-furo[4',3',2':4,5]naphtho[1,2-d][1,3]dioxol-5-one