31500-38-6 5-Norbornene-2,3-dicarboximide, N-ethyl-, (Z)-endo- NSC 68810 cis-3,6-Endomethylene-1,2,3,6-tetrahydrophthalic acid N-ethylimide cis-endo-N-Ethyl-5-norbornene-2,3-dicarboximide