(1R*,5R*,7R*,8S*)‐3‐(3,4‐Dihydroxy­benzo­yl)‐4‐hydr­oxy‐8‐methyl‐1,5,7‐tris­(3‐methyl‐2‐buten­yl)‐8‐(4‐methyl‐3‐penten­yl)bicyclo­[3.3.1]non‐3‐ene‐2,9‐dione