2-Butenoic acid, 2-methyl-, (1aR,2R,3S,4aR,6S,7S,7aS,8E,10R,11R,11aS)-2,7-bis(acetyloxy)-1,1a,2,3,4,6,7,10,11,11a-decahydro-11-hydroxy-1,1,3,6,9-pentamethyl-4-oxo-4a,7a-epoxy-5H-cyclopenta(a)cyclopropa(f)cycloundecen-10-yl ester, (2E)- 82513-30-2