4,7-Epoxyisobenzofuran-1,3-dione, 3a,4,7,7a-tetrahydro-, (3a.alpha.,4.beta.,7.beta.,7a.alpha.)- 6118-51-0 7-Oxabicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic anhydride, exo- NSC144085