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We synthesized and tested 3-chlorotyramine as a ligand of the D2 dopamine receptor. This compound displayed a similar affinity by this receptor to that previously reported for dopamine. In order to understand further the experimental results we performed a molecular modeling study of 3-chlorotyramine and structurally related compounds. By combining molecular dynamics simulations with semiempirical (PM6), ab initio and density functional theory calculations, a simple and generally applicable procedure to evaluate the binding energies of these ligands interacting with the D-2 dopamine receptors is reported here. These results provided a clear picture of the binding interactions of these compounds from both structural and energetic view points. A reduced model for the binding pocket was used. This approach allowed us to perform more accurate quantum mechanical calculations as well as to obtain a detailed electronic analysis using the Quantum Theory of Atoms in Molecules (QTAIM) technique. Molecular aspects of the binding interactions between ligands and the D-2 dopamine receptor are discussed in detail. A good correlation between the relative binding energies obtained from theoretical calculations and experimental IC50 values was obtained. These results allowed us to predict that 3-chlorotyramine possesses a significant affinity by the D-2-DR. Our theoretical predictions were experimentally corroborated when we synthesized and tested 3-chlorotyramine which displayed a similar affinity by the D-2-DR to that reported for DA.

Rabbit liver carboxylesterase (rCE) was evaluated as the catalyst for the enantioselective hydrolysis of (+/-)-3-endo-acetyloxy-1,8-cineole [(+/-)-4], which yields (1S,3S,4R)-(+)-3-acetyloxy-1,8-cineole [(+)-4] and (1R,3R,4S)-(-)-3-hydroxy-1,8-cineole [(-)-3]. Enantioselective asymmetrization of meso-3,5-diacetoxy-1,8-cineol (5) gives (1S,3S,4R,5R)-(-)-3-acetyloxy-5-hydroxy-1,8-cineole (6), with high enantioselectivity. rCE has been chosen to perform both experiments and molecular modeling simulations. Docking simulations combined with molecular dynamics calculations were used to study rCE-catalyzed enantioselective hydrolysis of cineol derivatives. Both compounds were found to bind with their acetyl groups stabilized by hydrogen bond interactions between their oxygen atoms and Ser221.