2-Butenoic acid, 2-methyl-, 4,4a,5,6,7,8,8a,9-octahydro-3,4a,5-trimethyl-8-oxonaphtho(2,3-b)furan-4-yl ester, (4R-(4alpha(E),4abeta,5beta,8abeta))- 86537-99-7