(2E)-4-[(2S,17S)-12-Hydroxy-8,21,21-trimethyl-5-(3-methyl-2-buten-1-yl)-8-(4-methyl-3-penten-1-yl)-14,18-dioxo-3,7,20-trioxahexacyclo[15.4.1.02,15.02,19.04,13.06,11]docosa-4(13),5,9,11,15-pent aen-19-yl]-2-methyl-2-butenoic acid