{(4aS,5R,5aS,9aR,10aS)-4a-[(S)-1-(2-Benzyloxy-ethyl)-2-methyl-allyl]-2,2,5a-trimethyl-decahydro-naphtho[2,3-d][1,3]dioxin-5-ylmethoxy}-tert-butyl-dimethyl-silane