(4aS)-1,4aβ-dimethyl-4,4a,7,8-tetrahydronaphthalene-2,5(3H,6H)-dione-5-ethyeneacetal

((1R,2R,4aS,8aS)-5-Formyl-1,2,4a-trimethyl-1,2,3,4,4a,7,8,8a-octahydro-naphthalen-1-yl)-acetic acid ethyl ester