A comparative molecular modeling study of dydrogesterone with other progestational agents through theoretical calculations and nuclear magnetic resonance spectroscopy

6-Dehydroretroprogesterone (dydrogesterone) and three other natural or synthetic progestins (progesterone, retroprogesterone, and 6-dehydroprogesterone) were submitted to a conformational study through theoretical calculations at the B3LYP/6-31G* level and high field NMR spectroscopy. The study allows to define the role of the two structural features which differentiate these steroids, i.e., the C9 and C10 configuration and the C6–C7 unsaturation. The combined effects of the conformational preference of A ring, determined by the configuration at C9 and C10, and the enhanced rigidity due to the C6–C7 double bond, could account both for the higher activity and selectivity of dydrogesterone with respect to the other three steroids.