The stereochemical outcome of the epoxidation of Δ14–15 cholestanes with mCPBA is controlled by the steric bulk of a C17 substituent. When the C17 is in the β configuration, the epoxide is formed in the α face, whereas if the C17 is trigonal (flat) or the substituent is in the α configuration, the epoxide is formed in the β face. The presence of a hydroxyl substituent at C20 does not influence the
Δ 14-15胆甾烷与 mCPBA 环氧化的立体
化学结果由 C17 取代基的空间位阻控制。当C17为β构型时,在α面形成
环氧化物,而如果C17为三角形(平)或取代基为α构型,则在β面形成
环氧化物。C20 处羟基取代基的存在不影响环氧化的立体
化学结果。