(4R)-5-[(1a'S,2R,3a'R,4'R,7a'S,10a'S)-4'-(acetyloxy)-3'-methylidene-1a',2',3',3a',7a',8',9',10a'-octahydro-4'H-spiro[oxirane-2,10'-oxireno[6,7]cyclonona[1,2-c]pyran]-7'-yl]-2-methylpent-2-ene-4,5-diyl diacetate