Conformational Analysis of 19-Oxygenated Steroids with a 4-Ene or 2, 4-Diene Structure, Potential Intermediates of Aromatase Reaction, with Semiempirical Molecular Orbital PM3 Calculations

Abstract

Conformational analysis of potent competitive inhibitors of aromatase, androst-4-enes 5, as well as 2, 4-diene steroids 3, 4, and 6 was carried out, using theoretical calculations, to determine the stereochemistry of their aromatase-catalyzed oxygenation. In the steroids examined, both the 19-alcohols and the 19-aldehydes favor the above-A ring conformation among the possible three in each. The results suggest that the 3-deoxy steroid 5a as well as the 2, 4-diene steroids 4a and 6a would be oxygenated at C-19 by aromatase through the same stereomechanism as that involved in the androstenedione aromatization.