Figure 1.

Structures of dafachronic acids synthesized in this study. The 25R isomers of each compound are shown in I-V, with important carbon atoms numbered and stereochemical features defined at C-5 and C-25. Beneath the structures are ball-and-stick models, which illustrate the differences in A/B-ring geometries among these compounds. The 19-methyl groups are highlighted by asterisks, and the 3-ketone oxygen atoms are indicated by arrowheads. Models were rendered by ChemBio 3D Ultra 11.0 after energy minimization with MM2.