2,2,3,3-tetramethoxy-1-oxaspiro<3.5>non-5-ene

methyl 2,2,3,3-tetramethoxycyclobutane-1-carboxylate

2,2,3,3-tetramethoxy-1-oxaspiro[3.5]nonane

2,2,3,3-tetramethoxy-6-methylpyran-4-one

脱氢乙酸