4-{(2R,3R)-3-[(1E,3E)-5-(tert-Butyl-dimethyl-silanyloxy)-4-methyl-penta-1,3-dienyl]-2,3-dimethyl-4-triisopropylsilanyloxy-2,3-dihydro-benzofuran-7-yl}-4-hydroxy-2-methoxy-3-methyl-cyclobut-2-enone