(4aR,5aS,10aR,11aS)-9-[(2R,3S,5R,6S)-5-Benzyloxy-6-benzyloxymethyl-3-(naphthalen-2-ylmethoxy)-tetrahydro-pyran-2-ylmethyl]-2,2-di-tert-butyl-4a,5a-dimethyl-octahydro-1,3,5,8,10-pentaoxa-2-sila-cyclohepta[b]naphthalene