1-[(3aR,3bS,5aS,5bS,8aR,9aS,9bS,11aS)-3a,5a,7,7-tetramethyltetradecahydro-5bH-[1]benzothieno[5',4':4,5]indeno[1,2-d][1,3]dioxol-5b-yl]ethanone