Epalons: Synthesis of 7-norallopregnanolone

The title compound 2 was prepared from (20R)-pregn-5-ene-3 beta,20-diyl 3-a cetate 20-benzoate (3) via (20R)-3 beta-acetoxy-20-benzoyloxy-5-oxo-5,6-sec opregnan-6-oic acid (5) and (20R)-3 beta-acetoxy-20-benzoyloxy-7-nor-5 beta ,6 alpha-pregnane-6,5-carbolactone (6). An intermediate 7-norpregn-5-ene de rivative - (20R)-7-norpregn-5-ene-3 beta,20-diyl 3-acetate 20-benzoate (7) - was hydrogenated using diimide in statu nascendi. The inversion of config uration at carbon C-3 was carried out via (20R)-7-nor-5 alpha-pregnane-3 be ta,20-diyl 3-tosylate 20-benzoate (12) and (20R)-7-nor-5 alpha-pregnane-3 a lpha,20-diyl 20-benzoate 3-formate (13).