An analog with high similarity to the transition state of the ene reaction between 1-alkenes and maleimide has been designed and synthesized. The reaction mechanism was studied using propene as a representative 1-alkene. The MP2/6-31G*//HF/6-31G* level of accuracy was used for the ab initio reaction modeling. Although the semiempirical AM1 method does not provide accurate reaction energetics, the transition state geometries were found to be in good agreement with the corresponding HF/6-3lG* structures. The endo transition state of the reaction between 1-butene and maleimide was used for the analog design. The structures for both transition state and its putative analogs were optimized using the AM1 method. The transition state and its analogs were compared by rigid body field fitting. The X-ray structure of the analog suggests a reasonable agreement between the computational and the experimental results. The analog is now used as a hapten to obtain catalytic antibodies.