{(2S,3R,5S,6R)-5-Benzyloxy-6-benzyloxymethyl-2-[(4aS,6R,7S,9aR)-7-(4-methoxy-benzyloxy)-octahydro-1,5-dioxa-benzocyclohepten-6-ylmethyl]-tetrahydro-pyran-3-yloxy}-triethyl-silane