2-Oxabicyclo[2.2.1]heptane-1-carboxylic acid, 4,7,7-trimethyl-3-oxo-,2-[3-(4-methoxyphenyl)-1,3,4,5,6,7-hexamethylbicyclo[2.2.1]hept-5-en-2-ylidene]ethyl ester