11-(tert-butyl-dimethyl-silanyloxy)-7-[1-(tert-butyl-dimethyl-silanyloxy)-3-(4-methyl-3,6-dihydro-2H-pyran-2-yl)-allyl]-15-methyl-13-methylene-6,21-dioxa-bicyclo[15.3.1]henicosa-3,9,19-trien-5-one