In order to determine the configuration at C₂₀ of γ-sitosterol by the conventional chemical method of correlation of configuration,a synthesis of 24-ethyl cholesterol using hyodesoxycholic acid (Ⅳ) as the starting material has been carried out.The series of reactions involved is as follows:IV→Va→Vb→Vc→Vd →VIc→VIf→Ⅷ→VIg→VIh→VIi→24-ethyl cholesterol.However,the final product was found to be β-sitosterol instead of the expected 24-iso-β-sitosterol.