Translational energy release and stereochemistry of steroids 4—Epimeric 3‐keto and 3‐hydroxy steroids

The translational energy, T , released during CH 3 ˙ loss from the molecular ions of epimeric steroid ketones and from both molecular and [M‐H 2 O] + ˙ ions of epimeric alcohols of the androstane, pregnane and cholestane series, differing in the mode of the A / B ring junction, has been measured. These data provide a simple and rapid method for identifying the configuration of the epimeric centres. Of the compounds studied, it is found in 3‐hydroxy steroids that the 5β‐isomers release the smaller amounts of translational energy for CH 3 ˙ loss. In most of the 3‐keto steroids investigated, the opposite is found, i.e. the larger T values are observed for the 5β‐isomers. Exceptions occur when further keto groups are introduced at the 11‐ or 17‐positions. A small range of epimeric pairs of 17‐hydroxy, 17‐keto and 4‐keto steroids have also been studied, the 5β‐isomer giving the lower T value in each case. The importance of hydroxy and keto groups at the various sites within the steroid structure in determining the T values is discussed.