[4aS,(-)]-1,4,4a,5,6,6a,9,13,13aβ,13b-Decahydro-4aβ-hydroxy-12-methoxy-4,4,6aβ,8,13bα-pentamethyl-2H-benzo[a]furo[3,4-i]xanthene-3,11-dione