Suggested Reaction 1.3.4.-

Left

11beta,21-Dihydroxy-3,20-dioxo-4-pregnen-18-al
+1,4-Dithiothreitol

Right

11beta,21-Dihydroxy-3,20-oxo-5beta-pregnan-18-al
+Oxidized dithiothreitol

[BiSSCat | GREP ]