3a,4,5,6,6a,7,9,10-Octahydro-8-hydroxy-α,3,3,11,11-pentamethyl-13-(3-methylbutyl)-7,15-dioxo-1,5-methano-3H,11H-furo[3,4-g]pyrano[3,2-b]xanthene-1-butanal