39622-53-2;(1.alpha.,2.alpha.,4.alpha.,7.alpha.)-3-Oxatricyclo[5.1.0.0(2,4)]-oct-5-ene-6,7-dicarboxylic acid dimethylester;(1alpha,2alpha,4alpha,7alpha)-3-Oxatricyclo(5.1.0.0(2,4))oct-5-ene-6,7-dicarboxylic acid dimethyl ester