(2aR,4S,4aS,6R,9S,11S,12S,12aR,12bS)-12b-(Acetyloxy)-12-(benzoyloxy)-1,2a,3,4,4a,6,9,10,11,12,12a,12b-dodecahydro-9,11-dihydroxy-4a,8,13,13-tetramethyl-4,6-bis[(triethylsilyl)oxy]-7,11-methano-5H-cyclodeca[3,4]benz[1,2-b]oxet-5-one-