(1R,2S,4aR,5S,6R,8S,8aR)-8-(Acetyloxy)-8a-[(acetyloxy)methyl]-5-[(2S,3aR,6aS)-hexahydrofuro[2,3-b]furan-2-yl]octahydro-5,6-dimethylspiro[naphthalene-1(2H),2′-oxiran]-2-yl 2-methylpropanoate