(2’S,4aS,4bS,6aS,7aS,8aS,8bS,8cR,8dS,9aR)-4a,6a-dimethylhexadecahydro-3’H-spiro[cyclopropa[4,5]cyclopenta[1,2-a]cyclopropa[l]phenanthrene-7,2′-furan]-2,5′(3H,4’H)-dione