(1S,2R,4S,4aS,5S,6R,8aR)-6-Benzyloxy-5-benzyloxymethyl-1-(tert-butyl-dimethyl-silanyloxymethyl)-2,4-dihydroxy-4a-(2-trimethylsilanyl-ethoxymethoxymethyl)-decahydro-naphthalene-1-carboxylic acid methyl ester