Bis[(1S,1'S,4R,4'R)-4,7,7-trimethyl-3-oxo-2-oxabicyclo[2.2.1]heptane-1-carboxylic acid] (9R,10R)-4,8,8-trimethyl-2-oxo-9,10-dihydro-2H,8H-benzo[1,2-b:3,4-b']dipyran-9,10-diyl ester