(3E,3aS,4R,6S,7S,7aR) methyl 3a-acetoxy-7-<(t-butyldimethylsilyl)oxy>-6-hydroxy-3-iodomethylidene-6-methyl-octahydrobenzofuran-4-carboxylate 生成 (3E,3aS,4R,7S,8S,8aR) 3a-acetoxy-8-<(t-butyldimethylsilyl)oxy>-3-iodomethylidene-7-methyl-hexahydro-4,7-methanofuro<2,3.d>oxepin-5-(4H)-one