Treatment of 3-oxo-4, 5-oxido steroids with lead tetraacetate results in acetoxylation in the 2α-position as could be shown by independent synthesis of the acetoxylated compounds. The products of this reaction rearrange even under very mild conditions (chromatography on silicagel or alumina) to the corresponding 2,3-dioxo-Δ4 compounds. The influence of structure and conformation of the various intermediates
用四
乙酸铅处理3-oxo-4,5-氧化甾体会导致2α-位的乙酰氧基化,这可以通过乙酰氧基化化合物的独立合成来证明。该反应的重新排列,即使在非常温和的条件(在
硅胶或氧化铝层析)为相应的2,3-二氧代Δ产品4的化合物。讨论了各种中间体的结构和构象对其NMR光谱的影响。提出了这种新转变的机制。