Suggested Reaction 1.3.4.-

Left

17alpha,21-Dihydroxy-4-pregnene-3,11,20-trione
+1,4-Dithiothreitol

Right

17alpha,21-Dihydroxy-5beta-pregnane-3,11,20-trione
+Oxidized dithiothreitol

[BiSSCat | GREP ]