Parameterization and validation of Gromos force field to use in conformational analysis of epoxidic systems

In order to study the conformational space of new natural products derivatives using molecular mechanics (MM) and molecular dynamics (MD), the Gromos force field has been expanded to include epoxidic systems. The parameterization and validation of Gromos were done to simulate 22, 23 epoxides in brassinosteroids analogs. The parameters were derived with an emphasis on the dependence between energy and dihedral angle due to its relevance in the conformational analysis. Molecular dynamics simulations of two model systems similar to those of interest were performed to validate the force field with the proposed parameters. Excellent agreement has been obtained between the MD simulation and the results of a potential energy surface (PES) calculated at B3LYP/6-31G∗∗ level.