(4aR,6S,7R,8aS)-6-{4-[(2R,3S,5R,6S)-5-Benzyloxy-6-(2-benzyloxy-ethyl)-3-(tert-butyl-dimethyl-silanyloxy)-tetrahydro-pyran-2-yl]-but-2-ynyl}-7-(tert-butyl-dimethyl-silanyloxy)-2,2,4a-trimethyl-hexahydro-pyrano[3,2-d][1,3]dioxine