Conformational free energy differences in steroids. Part VI. Intramolecular electrostatic interactions in 3-azidocholestan-6-ones: conformational preference of the azido-group

Abstract

Equilibrations of 3α- and 3β-azido-5α-cholestan-6-ones with their 5β-isomers were influenced by intramolecular electrostatic interactions between the azide and ketone groups. Calculated values for these interactions were in reasonable accord with the experimental findings. N.m.r. spectroscopic examination of cyclohexyl azide at –80° in carbon disulphide, [²H₄]methanol, and [²H₈]toluene provided a value for the conformational preference of the azido-group; the most accurate figure was 0·80 ± 0·06 kcal mol^–1 for 2M-solutions in carbon disulphide. Differences between the conformational preferences of the azido-, isocyanato-, and isothiocyanato-groups are discussed.