127331-49-1 5-Ethyl 7-oxabicyclo(2.2.1)heptane-2,3,5-tricarboxylate (2-exo,3-exo,5-endo)- 5-endo-(Ethoxycarbonyl)endothall 7-Oxabicyclo(2.2.1)heptane-2,3,5-tricarboxylic acid, 5-ethyl ester, (2-exo,3-exo,5-endo)-