(2’S,4aR,4bS,6aS,7aS,8aS,8bS,8cR)-4a,6a-dimethyl-4,4a,4b,5,6,6a,8,8a,8b,8c-decahydro-2H,3’H-spiro[cyclopropa[4,5]cyclopenta[1,2-a]phenanthrene-7,2′-furan]-2,5′(3H,4’H,7aH)-dione