(E)-(S)-5-(tert-Butyl-dimethyl-silanyloxy)-7-[(1R,2S,3R,5S)-5-(tert-butyl-dimethyl-silanyloxy)-3-triethylsilanyloxy-2-(2-triethylsilanyloxy-ethyl)-cyclopentyl]-hept-6-enoic acid methyl ester