(3aS,5S,8R,9aS,10S,12S,13aR,13bS)-6,9a,14,14-tetramethyl-13-methylene-2,9-dioxo-5,10-bis((triethylsilyl)oxy)-5,8,9,9a,10,11,12,13,13a,13b-decahydro-4H-3a,7-methanobenzo[3,4]cyclodeca[1,2-d][1,3]dioxole-8,12-diyl diacetate