2,2-dimethyl-propionic acid 2-[6-{7-[4-(tert-butyl-dimethyl-silanyloxy)-6-(3-iodo-allyl)-3-methyl-tetrahydro-pyran-2-yl]-6-methyl-hepta-1,4,6-trienyl}-3-(tert-butyl-dimethyl-silanyloxymethyl)-4-hydroxy-3-methyl-tetrahydro-pyran-2-yl]-ethyl ester