tri-tert-butyl [1S,1(4S,5R),3S,4S,5R,6R,7R]-1-(4-acetoxy-5-methyl-3-methylene-6-phenylhexyl)-7-(tert-butoxycarbonyl)oxy-4,6-dihydroxy-2,8-dioxabicyclo[3.2.1]octane-3,4,5-tricarboxylate