Showing structure for [1aR-(1aalpha,4beta,4abeta,5beta,9aS*)]-1a,2,4,4a,5,9-Hexahydro-4,4a,6-trimethyl-9-oxo-3H-oxireno[8,8a]naphtho[2,3-b]furan-5-yl ester 3-methyl-2-butenoic acid