(2aR,4S,4aS,6R,11S,12S,12aR,12bS)-12-benzoyloxy-11-hydroxy-4a,8,13,13-tetramethyl-5-oxo-4-triethylsilyloxy-3,4,4a,5,6,9,10,11,12,12a-decahydro-1H-7,11-methanocyclodeca[3,4]benzo[1,2-b]oxete-6,12b(2aH)diyl diacetate