Crystal and molecular structure of 18α-glycyrrhetinic acid

Abstract

The crystal structure of 18α-glycyrrhetinic acid (trans junction of the D/E rings) has been determined in order to compare its stereochemical features with those of the known 18β form (cis junction of the D/E rings). The two stereoisomers exhibit different physiological actions. A comparison of their common moieties shows significant differences between the conformations of the unsaturated C ring, with some torsion angles differing by more than ten degrees. Further differences involve the convexity of the ABCD region, which in the α form is smaller than that observed in the β isomer, and smaller than that reported for the mean steroid configuration.