(3S,3aS,6aR,7R,8R,9R,9aR,10aR,12R,12aS)-8-((tert-butyldimethylsilyl)oxy)-2,7,10,10,12-pentamethyl-5,13-dioxo-6a,7,9,9a,10,10a,11,12-octahydro-3H,8H-9,12a-methanocyclopenta[1,10]cyclopropa[6,7]cyclodeca[1,2-d][1,3]dioxol-3-yl acetate