(2R,4S,6E,8E,10E)-1-(4-methoxy-5-methylidene-2-oxo-2,5-dihydrofuran-3-yl)-2,4-dimethyldodeca-6,8,10-triene-1,5-dione = (1R,3R,6S,7E,10S,12R)-17-methoxy-3,10,12-trimethyl-16-oxatricyclo[12.2.1.0(1,6)]heptadeca-4,7,14(17)-triene-9,13,15-trione — reaction