(2R,3aS,5aS,6R,10bS,10cR)-2,6-dihydroxy-3a,10b-dimethyl-7-(propan-2-yl)-1,2,3,3a,5a,6,10b,10c-octahydro-4H,9H-[2]benzofuro[7,1-fg]isochromene-4,9-dione