6-[(1E,3E,5E)-6-[(1R,2R,3R,5R,7R,8R)-7-ethyl-2,8-dihydroxy-1,8-dimethy l-4,6-dioxabicyclo[3.3.0]oct-3-yl]hexa-1,3,5-trienyl]-4-methoxy-5-meth yl-pyran-2-one