2,2-Dimethyl-propionic acid (E)-(3R,4R,5R,6R,9S,13R,15R)-5-(tert-butyl-dimethyl-silanyloxy)-9,15-dimethoxy-4,6,13-trimethyl-3-triethylsilanyloxy-16-trityloxy-hexadec-10-enyl ester