methyl (4'S,4'aS,7'R,8'aR)-4',7'-dimethyl-2'-oxospiro[1,3-dioxolane-2,6'-3,4,5,7,8,8a-hexahydrochromene]-4'a-carboxylate 生成
methyl (4'aS,7'R,8'aR)-4',7'-dimethyl-3'-prop-2-enoxyspiro[1,3-dioxolane-2,6'-5,7,8,8a-tetrahydro-2H-chromene]-4'a-carboxylate